WO1996023229A1 - Etchants for use in micromachining of cmos microaccelerometers and microelectromechanical devices and method of making the same - Google Patents
Etchants for use in micromachining of cmos microaccelerometers and microelectromechanical devices and method of making the same Download PDFInfo
- Publication number
- WO1996023229A1 WO1996023229A1 PCT/US1996/001343 US9601343W WO9623229A1 WO 1996023229 A1 WO1996023229 A1 WO 1996023229A1 US 9601343 W US9601343 W US 9601343W WO 9623229 A1 WO9623229 A1 WO 9623229A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- substrate
- mem
- improvement
- accelerometer
- proof mass
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/12—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by alteration of electrical resistance
- G01P15/123—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by alteration of electrical resistance by piezo-resistive elements, e.g. semiconductor strain gauges
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/0802—Details
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
- G01P2015/0822—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass
- G01P2015/0825—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass
- G01P2015/0828—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass the mass being of the paddle type being suspended at one of its longitudinal ends
Definitions
- the invention relates to the field of three-dimensional microstructures, and in particular, to accelerometers compatible with CMOS technology.
- MEMS micro electromechanical systems
- CMOS design rules so that digital circuits can be designed and fabricated using standardized design assumptions and so that the design can be translated and used with substantially different design rules and hence device parameters.
- CMOS wafers using maskless post processing. This is done by stacking an active area, both metal contact cuts, and over-glass cuts, to leave bare silicon exposed when the chips are returned from the foundry. See for example J. Marshall et
- thermopile converters M. Gaitan et al., "Performance of Commercial CMOS Foundry Compatible Multifunction Thermal Converters, " in Proc. 7th Int. Conf. on Solid State Sensors and Actuators (Transducers '93) Yokohama, June 7-10, 1993. at
- CMOS foundry has been used to make high voltage devices.
- Z. Parpia et al. "Modeling with CMOS Compatible High Voltage Device Structures, " in Proc. Symp. High Voltage and Smart Power Devices at 41-50 (1987), Absolute Temperature Sensors.
- the invention is an improvement in a method for fabricating microelectromechanical (MEM) devices.
- the improvement comprises the steps of providing a substantially completed MEM device except for the need of at least one unmasked etch to complete the device.
- the MEM device is etched with a generally isotropic etchant selected from the group of noble gas flourides and tetramethyl ammonium hydroxide. Xenon difluoride is the preferred gas phase etchant, but other flourides of xenon and of other noble gases could be equivalently substituted.
- the etching of the MEM device is performed with a gas phase xenon difluoride, the etching the MEM device is at ambient temperature without external heating, and is performed under a partial vacuum.
- the etching the MEM device is performed in a aqueous solution of tetramethyl ammonium hydroxide with silicic acid.
- the invention is a method for fabricating microelectromechanical (MEM) devices, using a standard integrated circuit (IC) process. comprised of the steps of providing a substantially completed MEM device except for the need of a single unmasked etch to complete the device, and etching the MEM device with xenon difluoride in a gas phase.
- the invention is also a microelectromechanical (MEM) accelerometer defined in a semiconductor substrate comprising a proof mass fabricated on the substrate using integrated circuit processes. At least one and preferably two oxide beams couple the proof mass to the substrate. The oxide beam is at least in part unsupported and extending from the proof mass to the substrate. At least one polysilicon piezoresistor is disposed in the oxide beam.
- the MEM accelerometer is inexpensively manufactured using standard integrated circ technology.
- the accelerometer comprises at least two unsupported oxide beams coupli the proof mass to the substrate.
- Each of the oxide beams has at least one polysilic piezoresistor disposed therein.
- the invention also includes a method of making three dimensional structures usi aluminum micro hinges.
- the hinge is used to create accelerometers wi sensitivity along orthogonal axes.
- the substrate is generally planar and the hinge is deform so that the proof mass is oriented in a predetermined position out of the plane of the substrat
- the accelerometer further comprises at least three of the proof mass fabricated from the substrate using integrated circuit processes and at one hinge.
- Each of t hinges couples a proof mass, support bean and peixoresistor to the substrate. At least one a possibly all three of the proof masses are oriented in a different plane relative to the substrate.
- the hinges are comprised of aluminum.
- the hinges are fabricated using xen difluoride as a gas-phase ambient temperature etchant to define the hinges apart from t substrate and proof mass.
- the hinges are fabricated using a tetrameth ammonium hydroxide aqueous solution with silicic acid to define the hinges apart from t substrate and proof mass.
- the proof mass, hinges, and polysilicon piezoresistor a formed using CMOS processes.
- the invention is also an improvement in a method of mass fabricating microelectromechanical device.
- the improvement comprises providing a device havi portions which must be oriented to predetermined three dimensional positions in order assume final configuration for said device, selected portions of said device having electrically isolat structures for receiving and holding charge for at least a temporary period. Selected amounts electric charge are selectively deposited on said electrically isolated structures to genera electrostatic forces therebetween to move selected portions of said device to assume said fin configuration according to well understood principles of mechanics and electrostati specifically applied to each device topology.
- a scanning electron microscope is used to deposit electron charges on the electrically isolated structures.
- the invention can still further be defined as an improvement in a microelectromechanical (MEM) device having a substrate and a movable part separate from the substrate comprising a derformable hinge coupling the substrate and part.
- the hinge is deformed so that the substrate and separate part form a three dimensional structure.
- the improvement further comprises a sensing element for generating a position signal indicative of the spatial orientation of the part, such as a piezoresistor, capacitive, magnetic or electron tunneling device.
- the improvement further comprises source of a force disposed on the substrate and part for deforming the hinge to form the three dimensional structure, such as a source of electrostatic charge, magnetic fields or thermally generated forces.
- the improvement further comprises a circuit disposed either on the substrate, part or both, which circuit is coupled to the sensing element for processing the position signal, such as sensing, amplifying, filtering controlling or otherwise interfacing to the sensing element or an actuator.
- a circuit disposed either on the substrate, part or both, which circuit is coupled to the sensing element for processing the position signal, such as sensing, amplifying, filtering controlling or otherwise interfacing to the sensing element or an actuator.
- the part is fabricated in a form or out of a substance so that it interacts with electromagnetic radiation, such as particle or x-ray radiation, visible, infrared, ultraviolet or other portions of the electromagnetic spectrum, to achieve a defined function.
- electromagnetic radiation such as particle or x-ray radiation, visible, infrared, ultraviolet or other portions of the electromagnetic spectrum
- Figure 1 is a simplified plan view of a first embodiment of a two beam accelerometer made according to the invention.
- Figure la is a longitudinal cross-sectional of the two beam accelerometer of Figure 1.
- Figure 2 is a schematic of the circuit for the accelerometer shown in Figure 1.
- Figure 3 is a simplified plan view of a second embodiment of a two beam acceleromete including aluminum hinges, made according to the invention.
- Figure 4 is a graph of the percentage change in resistance of the polysilicon strai gauges as a function of the vertical displacement of the surface of the accelerometer of Figure 1 and 3.
- Figure 5 is a graph of the percentage change in resistance of the polysilicon strai gauges as a function of the horizontal displacement of the surface of the accelerometer of Figur 3 after rotation to a plane orthogonal to the substrate.
- Figure 6 is an idealized perspective view of an MEM three dimensional accelerometer.
- Figure 7 is an idealized diagram showing one etching system in which the etchant of th invention is used.
- Figure 8 is an enlarged view of a plurality of plates supported by aluminum hinges mad according to the invention.
- Figure 9 is a side cross-sectional view of an aluminum hinge running between oxid plates and a polysilicon piezoresistor.
- the accelerometers are fabricated using a standard CMO foundry, such as 2 micron double poly, double metal p-well service, provided by Orb Semiconductor from MOSIS service.
- a standard CMO foundry such as 2 micron double poly, double metal p-well service, provided by Orb Semiconductor from MOSIS service.
- a typically accelerometer is shown diagrammatically in Figure 1 with piezoresistors 34 and each support beam 32.
- piezoresistors 34 typically perform two opposing arms of wheatstone bridge in combination with on chip resistors 46.
- the wheatstone bridge circuit typically provides low temperature sensitivity and good power supply rejection.
- the change in resistance is given by the product of the gauge factor of the piezoresistive polysilicon and the strain which the gauge experiences. The result is that the percentage change in output voltage for the wheatstone bridge is one-half the gauge factor times the strain in the gauges.
- the strain at any point in the beam is given by the equation below where M is the bending moment which is being sensed, X is the position along the beam, z is the vertical distance from the center axis, E the modulas elasticity and I the moment inertia of a rectangular cross section.
- An an n-type polysilicon piezoresistor has a gauge factor of roughly -20 with a p-type polysilicon piezoresistor having a gauge factor of between 20 and 30 depending upon grain size and doping.
- Polysilicon gauges are preferred because they are easy to protect during the sensor release etch. The polysilicon is protected by the surrounding oxides. It would also be possible to use the p+ or n+ regions of a type which are typically used as a source drain of FET's for the piezoresistive sensing elements.
- the gauge factor of p+ single crystal silicon is much higher than that of polysilicon by a factor of about 5 depending upon the orientation of the sensor.
- the p+ region is further from the neutral axis of the beam, thereby giving additional sensitivity.
- a dopant sensitive etchant such as EDP or TMAH must be used.
- a electrochemical etch stop could be used by biasing the p+ regions relative to the etcha solution during the etch. Acceleration is turned into a bending moment which in turn is turned into a materi strain, then a resistance change, and then finally a voltage change in the bridge.
- the resultin expression for the output voltage is given by the following equation where W is the width of t proof mass, Lp the length of the proof mass, a the support beam thickness, B the support bea width and A is the acceleration.
- Figure la is a longitudinal cross sectional view taken through sectional lines 4a-4a Figure 1.
- Proof mass 30 is shown as being formed of a sandwich of alternating layers of gla or oxide 47 and metalization 48 and passivated by glass encapsulation 50.
- Proof mass 30 coupled then through a glass and oxide connection 52 to the cantilever beam 32 which also i turn is made of a plurality of glass and oxide layers 47 in which a silicon piezoresistive eleme
- Figures 1 and 3 show designs of two variations of an accelerometer.
- the basic design each includes a proof mass 30 comprised of an oxide plate typically with etch holes and one more support beams 32 into which polysilicon piezoresistors 34 have been disposed.
- Metal a poly layers can also be used to increase the mass of the proof plate.
- the resistance change of the piezoresistors 34 was measured as a function of the ti displacement of these devices. Micromanipulators were used to deflect the tip of the plate a deflection was visually measured using microscope focus for the vertical displacement. T resistance change versus vertical deflection is shown in Figure 4 and the resistance change versus horizontal deflection for a rotated accelerometer is shown in Figure 5.
- electrical connection to the piezoresistor is measured through aluminum hinges 36.
- the resistance of the accelerometer strain gauges shown in Figures 1 and 3 as measured in Figures 4 and 5 was measured using a digital volt meter connected to a wire-wrapped amplifier board built with a gain of 1 ,000 and a bandwidth of DC to 10 Hertz.
- the external amplifier showed a 20 millivolt change when the accelerometer was rolled over from +lg to - lg.
- the 10 millivolt per g output signal corresponds to the deflection in the tens of nanometers per g.
- Polysilicon strain gauges were characterized using several different beam and plate geometries.
- An n-type gauge factor, G was found to vary between -10 and -20 over several tested runs.
- FIG. 6 diagrammatically shows an integrated circuit wafer and substrate in which three accelerometers generally denoted by reference numerals 38a-c are coupled via aluminum hinges 40a-c to an integrated circuit wafer 42 into which an on chip amplifier 44 and other signal conditioning circuitry has been formed.
- the circuitry of chip 44 may also include CMOS amplifiers, filters, analog-to-digital converters, temperature compensation circuitry, calibration circuitry, and digital processing circuitry of any type desired.
- the three axis version of the accelerometer design uses one planar accelerometer and two orthogonal hinged accelerometers, each with an integrated low noise CMOS amplifier 44.
- Each proof mass 30 is composed of a stack of all oxides and conductors for a total mass of 2.5 micrograms.
- the support hinges 40a-c extend to form or are coupled to a beam which contains a 1 kilo-ohm polysilicon piezoresistor 34.
- the total area of the three axis system was 4 square millimeters. Substantially better performance is expected to be realized with an integrated CMOS amplifier than an off chip amplified accelerometer.
- FIG. 6 With no external loading, the structures shown in Figure 6 could stand on their own held in place by aluminum hinges 40a-c. A micromanipulator or other external force is used to bend the hinges into the desired position.
- Rotated structures such as shown in Figure 6 can be mad with interlocking braces to keep the structure in the desired position by technique similar t those used with polysilicon structures as described by Pister, "Hinged Polysilicon Structure with Integrated Thin Film Transistors, " in Proc. IEEE Solid State Sensor and Actuato Workshop, Hiltonhead, South Carolina, June 22-25, 1992, at 136-39. Mass assembly of device as shown in Figure 6 can be achieved with the assistance of scanning electro microscopes.
- a beam of high energy electrons are used to deposit a specific amount of charg on an electrically isolated structure to electrostatically bend the hinges so that the structur assumes the final configuration.
- sensors and actuators have previously been demonstrated usin simple post-processing of standard CMOS technology. According to the invention, it is als now possible to assemble simple three-dimensional structures and integral piezoresistiv deflection for sensors. Additionally, a simple new gas-phase approach to CMOS proces etching can be used to fabricate the micromachined structures. With this extensive set o microelectromechanical elements, coupled with a tremendous library of electrical capabilitie available in CMOS technologies, it is possible to design and fabricate sophisticated systems in wide variety of applications with very rapid turnaround time.
- the hinged piezoresistive three-dimensional sensor or accelerometer of the illustrate embodiement can find applications immediately in many devices including but not limited to profilometer, an anemometer, magnetometer, hygrometer, electron tunneling sensors, and i cases where sensitivity is high enough in gyroscopic equipment.
- a new system has been developed which etches silicon highly selectively at moderat temperatures and without hydrodynamic forces potentially damaging to small structures an features. The system is based on the use of the gas phase etchant xenon diflouride, which is a unremarkable white solid at standard temperature and pressure.
- Aluminum hinges and polysilicon piezoresistors have been fabricated using a standard commercial CMOS process with one maskless post-processing step.
- the hinges and piezoresistors have been formed using the metal interconnect and transistor gate layers with CMOS processes.
- Surface machining with xenon diflouride (XeF2) is a simple and effective alternative to standard bulk etchings for this process because of its extreme selectivity and gentle gas-phase etch.
- Xenon diflouride has been synthesized since the early 1960's and is commercially available.
- xenon difluoride is different from the prior art in three major ways. The most significant of which is the highly selective nature of the etch. Semiconductor processing requires a great deal of etching done with as much selectivity and control as possible to produce useful patterns and structures. Xenon diflouride etches silicon preferentially over almost all tested materials which one could encounter in semiconductor processing.
- the second highly distinct feature of xenon diflouride is the gas phase nature of the etch.
- Gas phase etching allows for very gentle processing with no hydrodynamic forces. This gentle processing allows for the construction of thin oxide and metal structures by established processes which would otherwise be totally inaccessible using liquid phase etchants. Hydrodynamic forces in the liquid phase could damage even the grossest of such structures or at least many of the structures described here.
- This technique was originally conceived as a way to selectively etch silicon from standard CMOS technology chips to create microelectromechanical devices. In order to do this 12
- xenon difluoride and tetramethyl ammonium hydroxide hav been developed as extremely effective etchants for MEMS applications.
- One apparatus 10 f using the etchant is shown in Figure 7 where a chamber 12 connected by a valve 16 to a sourc 18 of xenon diflouride. Gas or nitrogen purging is also provided to chamber 12 through valv 20.
- valve 16 is opened and small amounts of xenon diflouride vaporize in the lo pressure and enter the vessel.
- the etch is performed in vapor phase at room temperature wit no external energy sources at a partial pressure of 1-4 Torr. Under these conditions, etch rat as high as 10 microns per minute have been observed with 1 to 3 microns per minute bein typical.
- the etch is isotropic and independent of silicon doping compounds as well as highl selective.
- this etching system introduces no hydrodynamic forces. It has been used by us to release microscopic mechanical structures hooked directly into accompanying electronics. The gentle nature of this etching system allows the researchers to etch silicon out from underneath silicon dioxide or metal hinges only a few microns wide and hundreds of microns long. This technique of etching allows for the construction of complicated micromechanical structures directly integrated on chip with analog and digital electronics; all at relatively low cost as the CMOS technological infrastructure is well established.
- TMAH tetramethyl ammonia hydroxide
- the etch is nearly isotropic.
- the primary differen between structures etched in liquid TMAH silicic acid solutions and structures etched in g phase xenon difluoride is the drying induced bending of the support beams.
- the aluminum hinge acts as a plastical deformable flexural hinge similar in function to the polyimide hinges described by Suzuki al., "Creation of an Insect Base Microrobot with an External Skeleton and Elastic Joints, " Proc. IEEE Microelectronic Mechanical Systems Workshop, Travemunde, Germany, Februa 4-7, 1992 at 190-95.
- the hinge is created by running a line of metal over bare silicon.
- T strain gauge is comprised of a polysilicon resistor protected from the etchant by surroundi oxides.
- a typical CMOS process will have an additional layer of metal and polysilicon shown in Figure 9 which is a simplified cross section of aluminum trace 22 running betwe oxide plates 24 and a contacting polysilicon piezoresistor 26.
- the oxide and first metal over-etch into silicon substrate 28 causes aluminum trace 22 be lower than oxides 24.
- all of the metal layers can be used make hinges, separately or in combination.
- much of the silicon substrate in the op areas is removed by the over-etch of the oxide and metal layers, resulting in metal traces whi are recessed into the substrate after fabrication as shown in Figure 9.
- the oxide plates and aluminum hinges will suspended over silicon pits.
- the multilayer structures are generally surprisingly fl considering the heterogeneity of the thin films. Strain gradient induced deflections are typica less than 10 microns for cantilevers with lengths less than 300 microns. On a recent r however, the tip deflection of a 300-micron oxide cantilever was over 100 microns. General this excessive curvature is undesirable.
- the resistance of loops of aluminum as shown in Figure 8 is between 1 and 2 oh before and after the etch. Aluminum can be deformed elastically over small range of moti 15
- An accelerometer is comprised of a proof mass and a force detection system.
- Existing silicon micromachined accelerometers are typically made from custom bulk micromachining processes which are designed to yield proof masses in the order of magnitude of milligrams.
- High performance accelerometers are typically either used for capacity of position sensing or force feedback sensing. Virtually all accelerometers use off-chip electronics to detect a condition the measured electrical signal.
- etchants of the invention and in particular, xenon difluoride are particularly advantageous when used to fabricate microelectromechanical devices using a polymer layer.
- Traditionally it has been difficult to integrate polymer layers into MEMS processes because of the tendancy of bulk and surface etchants to destroy the polymers. Because of the extreme selectivity of xenon difluoride, uses of many if not most of these polymers should now be possible.
Abstract
What is described in the present specification are accelerometers using tiny proff masses (30) and piezoresistive force detection. The devices may include deformable hinges (40a-c) to allow the fabrication of three dimensional structures. A new system has been developed which etches silicon highly selectively at moderate temperature and without hydrodynamic forces potentially damaging to small structures and features. The system is based on the use of the gas phase etchant xenon difluouride, which is an unremarkable white solid at standard temperature and pressure.
Description
ETCHANTS FOR USE IN MICROMACHINING OF CMOS MICROACCELEROMETERS
AND MICROELECTROMECHANICAL DEVICES
AND METHOD OF MAKING THE SAME
Background of the Invention
/. Field of the Invention
The invention relates to the field of three-dimensional microstructures, and in particular, to accelerometers compatible with CMOS technology.
2. Description of the Prior Art
The marriage of semiconductor fabrication technology with electromechanical microstructures has given rise to the theoretical possibility of a vast array of microsensors, microtransducers and microactuators that can potentially be made in large numbers at low cost to perform a wide variety of functions, particularly when integrally combined with integrated circuits.
However, the development of an application in micro electromechanical systems (MEMS) is often restricted by process-related barriers. Even conceptual designs can take a substantial amount of process development time. The development of a design for a device is typically coupled to process parameters, so that the process designer and the application designer must be in close communication, if not in fact, be the same person.
This is sharply contrasted with the state of integrated circuit design, in which it is possible to design good circuits without expert knowledge of the fabrication processes. Integrated circuit fabrication has produced scaleable CMOS design rules so that digital circuits can be designed and fabricated using standardized design assumptions and so that the design can be translated and used with substantially different design rules and hence device parameters.
Several research groups in Europe and North America have demonstrated that it is possible to micromachine commercial CMOS wafers using maskless post processing. This is done by stacking an active area, both metal contact cuts, and over-glass cuts, to leave bare silicon exposed when the chips are returned from the foundry. See for example J. Marshall et
5 al.. "Realizing Suspended Structures on Chips Fabricated by CMOS Foundry Processes Through MOS1S Service, " NISTIR 5402, U.S. National Institute of Standards and Technolog\ . Gaithersburg, Maryland 20899 (1994). The chips are then etched in EDP or some other anisotropic etchant. This technique was demonstrated in the late 1980's and has been used to produce a variety of micromachined components, including: infrared emitting arrays for thermal 0 scene simulation, M. Parameswaran et al., "Commercial CMOS Fabricated Integrated Dynamic Thermal Scene Simulator, " IEEE Int. Elec. Dev. Mtg., San Francisco. California, December 13-16, 1991, at 753-56; thermopile converters, M. Gaitan et al., "Performance of Commercial CMOS Foundry Compatible Multifunction Thermal Converters, " in Proc. 7th Int. Conf. on Solid State Sensors and Actuators (Transducers '93) Yokohama, June 7-10, 1993. at
15 1012-14; thermal actuators. M. Parameswaran et al., "CMOS Electrothermal Microactuator, " in Proc. IEEE Microelectro Mechanical Systems Workshop, Napa. California. February 1 1-14. 1990, at 128-31, flow sensors. D. Moser, "CMOS Flow Sensors, " Ph.D. Thesis ETH Zurich. Physical Electronics Laboratory, Swiss Federal Institute of Technology, Zurich, Switzerland, and resonant hygrometers, T. Boltshauser et al., "Piezoresistive Membrane Hygrometers
20 Based on IC Technology, " Sensors and Materials, 5(3): 125-34 (1993) and H. Baltes, "CMOS as a Sensor Technology, " Sensors and Actuators A37-38.51-6 (1993).
Additionally, CMOS foundry has been used to make high voltage devices. Z. Parpia et al., "Modeling with CMOS Compatible High Voltage Device Structures, " in Proc. Symp. High Voltage and Smart Power Devices at 41-50 (1987), Absolute Temperature Sensors. P.
25 Krummenacher et al., "Smart Temperature Sensor in CMOS Technology, " Sensors and Actuators. A21-23:636-38 (1990). Invisible Light Imaging Arrays. This impressive list of sensors and actuators comes packaged along with all the analog and digital electronics available
in the foundry process. Nevertheless, two limitations of this approach has been the constraints imposed by etching and limited structural components.
Therefore, what is needed is a micromachining process useful in a wide variety of applications and devices, including but not limited to accelerometers, that will allow engineers and scientists from many different disciplines to create new micro electromechancial systems and applications, particularly using post process foundry CMOS wafers.
Brief Summary of the Invention
The invention is an improvement in a method for fabricating microelectromechanical (MEM) devices. The improvement comprises the steps of providing a substantially completed MEM device except for the need of at least one unmasked etch to complete the device. The MEM device is etched with a generally isotropic etchant selected from the group of noble gas flourides and tetramethyl ammonium hydroxide. Xenon difluoride is the preferred gas phase etchant, but other flourides of xenon and of other noble gases could be equivalently substituted. In the embodiment where the etching of the MEM device is performed with a gas phase xenon difluoride, the etching the MEM device is at ambient temperature without external heating, and is performed under a partial vacuum.
In an alternative embodiment the etching the MEM device is performed in a aqueous solution of tetramethyl ammonium hydroxide with silicic acid. Somewhat more specifically the invention is a method for fabricating microelectromechanical (MEM) devices, using a standard integrated circuit (IC) process. comprised of the steps of providing a substantially completed MEM device except for the need of a single unmasked etch to complete the device, and etching the MEM device with xenon difluoride in a gas phase. The invention is also a microelectromechanical (MEM) accelerometer defined in a semiconductor substrate comprising a proof mass fabricated on the substrate using integrated circuit processes. At least one and preferably two oxide beams couple the proof mass to the substrate. The oxide beam is at least in part unsupported and extending from the proof mass to
the substrate. At least one polysilicon piezoresistor is disposed in the oxide beam. As a resu the MEM accelerometer is inexpensively manufactured using standard integrated circ technology.
Preferably the accelerometer comprises at least two unsupported oxide beams coupli the proof mass to the substrate. Each of the oxide beams has at least one polysilic piezoresistor disposed therein.
The invention also includes a method of making three dimensional structures usi aluminum micro hinges. In one embodiment, the hinge is used to create accelerometers wi sensitivity along orthogonal axes. The substrate is generally planar and the hinge is deform so that the proof mass is oriented in a predetermined position out of the plane of the substrat In one embodiment the accelerometer further comprises at least three of the proof mass fabricated from the substrate using integrated circuit processes and at one hinge. Each of t hinges couples a proof mass, support bean and peixoresistor to the substrate. At least one a possibly all three of the proof masses are oriented in a different plane relative to the substrate. The hinges are comprised of aluminum. The hinges are fabricated using xen difluoride as a gas-phase ambient temperature etchant to define the hinges apart from t substrate and proof mass. Alternatively, the hinges are fabricated using a tetrameth ammonium hydroxide aqueous solution with silicic acid to define the hinges apart from t substrate and proof mass. Specifically, the proof mass, hinges, and polysilicon piezoresistor a formed using CMOS processes.
The invention is also an improvement in a method of mass fabricating microelectromechanical device. The improvement comprises providing a device havi portions which must be oriented to predetermined three dimensional positions in order assume final configuration for said device, selected portions of said device having electrically isolat structures for receiving and holding charge for at least a temporary period. Selected amounts electric charge are selectively deposited on said electrically isolated structures to genera electrostatic forces therebetween to move selected portions of said device to assume said fin configuration according to well understood principles of mechanics and electrostati
specifically applied to each device topology. In the illustrated embodiment a scanning electron microscope is used to deposit electron charges on the electrically isolated structures.
The invention can still further be defined as an improvement in a microelectromechanical (MEM) device having a substrate and a movable part separate from the substrate comprising a derformable hinge coupling the substrate and part. The hinge is deformed so that the substrate and separate part form a three dimensional structure.
The improvement further comprises a sensing element for generating a position signal indicative of the spatial orientation of the part, such as a piezoresistor, capacitive, magnetic or electron tunneling device. The improvement further comprises source of a force disposed on the substrate and part for deforming the hinge to form the three dimensional structure, such as a source of electrostatic charge, magnetic fields or thermally generated forces.
The improvement further comprises a circuit disposed either on the substrate, part or both, which circuit is coupled to the sensing element for processing the position signal, such as sensing, amplifying, filtering controlling or otherwise interfacing to the sensing element or an actuator.
In some embodiments the part is fabricated in a form or out of a substance so that it interacts with electromagnetic radiation, such as particle or x-ray radiation, visible, infrared, ultraviolet or other portions of the electromagnetic spectrum, to achieve a defined function. The invention may be better visualized by now turning to the following drawings wherein like elements are referenced by like numerals.
Brief Description of the Drawings
Figure 1 is a simplified plan view of a first embodiment of a two beam accelerometer made according to the invention.
Figure la is a longitudinal cross-sectional of the two beam accelerometer of Figure 1. Figure 2 is a schematic of the circuit for the accelerometer shown in Figure 1.
Figure 3 is a simplified plan view of a second embodiment of a two beam acceleromete including aluminum hinges, made according to the invention.
Figure 4 is a graph of the percentage change in resistance of the polysilicon strai gauges as a function of the vertical displacement of the surface of the accelerometer of Figure 1 and 3.
Figure 5 is a graph of the percentage change in resistance of the polysilicon strai gauges as a function of the horizontal displacement of the surface of the accelerometer of Figur 3 after rotation to a plane orthogonal to the substrate.
Figure 6 is an idealized perspective view of an MEM three dimensional accelerometer. Figure 7 is an idealized diagram showing one etching system in which the etchant of th invention is used.
Figure 8 is an enlarged view of a plurality of plates supported by aluminum hinges mad according to the invention.
Figure 9 is a side cross-sectional view of an aluminum hinge running between oxid plates and a polysilicon piezoresistor.
The invention as described in the context of the illustrated embodiment as well various other embodiments can now be understood by turning to the following detaile description.
Detailed Description of the Preferred Embodiments
What is described in the present specification are accelerometers using tiny pro masses and piezoresistive force detection. Conventional wisdom would indicate that th approach would not yield useful sensors. However, in fact, according to the invention, suc devices are suitable in a wide range of applications. In the illustrated embodiment, the accelerometers are fabricated using a standard CMO foundry, such as 2 micron double poly, double metal p-well service, provided by Orb Semiconductor from MOSIS service. When an additional etching step is performed on th
chips after they are received from the CMOS fabricator to free the acceleration sensing element without harming the existing electronics on the chip. Using standard process and existing fabrication facilities, fabrication costs for tested chips is well below one dollar in comparison to currently existing accelerometers having a comparable performance, which accelerometers typically cost between 30 and 300 dollars.
A typically accelerometer is shown diagrammatically in Figure 1 with piezoresistors 34 and each support beam 32. As shown in the schematic of Figure 2, piezoresistors 34 typically perform two opposing arms of wheatstone bridge in combination with on chip resistors 46. The wheatstone bridge circuit typically provides low temperature sensitivity and good power supply rejection. The change in resistance is given by the product of the gauge factor of the piezoresistive polysilicon and the strain which the gauge experiences. The result is that the percentage change in output voltage for the wheatstone bridge is one-half the gauge factor times the strain in the gauges. In a simplified model, the strain at any point in the beam is given by the equation below where M is the bending moment which is being sensed, X is the position along the beam, z is the vertical distance from the center axis, E the modulas elasticity and I the moment inertia of a rectangular cross section.
An an n-type polysilicon piezoresistor has a gauge factor of roughly -20 with a p-type polysilicon piezoresistor having a gauge factor of between 20 and 30 depending upon grain size and doping. Polysilicon gauges are preferred because they are easy to protect during the sensor release etch. The polysilicon is protected by the surrounding oxides. It would also be possible to use the p+ or n+ regions of a type which are typically used as a source drain of FET's for the piezoresistive sensing elements. The gauge factor of p+ single crystal silicon is much higher than that of polysilicon by a factor of about 5 depending upon the orientation of the sensor. In addition, the p+ region is further from the neutral axis of
the beam, thereby giving additional sensitivity. To release the structure while preserving the p region, a dopant sensitive etchant such as EDP or TMAH must be used. Alternatively, a electrochemical etch stop could be used by biasing the p+ regions relative to the etcha solution during the etch. Acceleration is turned into a bending moment which in turn is turned into a materi strain, then a resistance change, and then finally a voltage change in the bridge. The resultin expression for the output voltage is given by the following equation where W is the width of t proof mass, Lp the length of the proof mass, a the support beam thickness, B the support bea width and A is the acceleration. L
V . -b 2 W f
•^ • A
Figure la is a longitudinal cross sectional view taken through sectional lines 4a-4a Figure 1. Proof mass 30 is shown as being formed of a sandwich of alternating layers of gla or oxide 47 and metalization 48 and passivated by glass encapsulation 50. Proof mass 30 coupled then through a glass and oxide connection 52 to the cantilever beam 32 which also i turn is made of a plurality of glass and oxide layers 47 in which a silicon piezoresistive eleme
34 has been embedded at a distance z off the center or neutral axis of beam 32. Figures 1 and 3 show designs of two variations of an accelerometer. The basic design each includes a proof mass 30 comprised of an oxide plate typically with etch holes and one more support beams 32 into which polysilicon piezoresistors 34 have been disposed. Metal a poly layers can also be used to increase the mass of the proof plate. By adding a support pla and aluminum hinges 36, the design of Figure 1 can be rotated out of the plane of the wafer shown in the design of Figure 3.
The resistance change of the piezoresistors 34 was measured as a function of the ti displacement of these devices. Micromanipulators were used to deflect the tip of the plate a deflection was visually measured using microscope focus for the vertical displacement. T
resistance change versus vertical deflection is shown in Figure 4 and the resistance change versus horizontal deflection for a rotated accelerometer is shown in Figure 5.
In the embodiment of Figure 3, electrical connection to the piezoresistor is measured through aluminum hinges 36. The resistance of the accelerometer strain gauges shown in Figures 1 and 3 as measured in Figures 4 and 5 was measured using a digital volt meter connected to a wire-wrapped amplifier board built with a gain of 1 ,000 and a bandwidth of DC to 10 Hertz. Using a wheatstone bridge configuration with a half bridge on chip, the external amplifier showed a 20 millivolt change when the accelerometer was rolled over from +lg to - lg. The 10 millivolt per g output signal corresponds to the deflection in the tens of nanometers per g.
Polysilicon strain gauges were characterized using several different beam and plate geometries. An n-type gauge factor, G, was found to vary between -10 and -20 over several tested runs.
Figure 6 diagrammatically shows an integrated circuit wafer and substrate in which three accelerometers generally denoted by reference numerals 38a-c are coupled via aluminum hinges 40a-c to an integrated circuit wafer 42 into which an on chip amplifier 44 and other signal conditioning circuitry has been formed. The circuitry of chip 44 may also include CMOS amplifiers, filters, analog-to-digital converters, temperature compensation circuitry, calibration circuitry, and digital processing circuitry of any type desired. The three axis version of the accelerometer design uses one planar accelerometer and two orthogonal hinged accelerometers, each with an integrated low noise CMOS amplifier 44. Each proof mass 30 is composed of a stack of all oxides and conductors for a total mass of 2.5 micrograms. The support hinges 40a-c extend to form or are coupled to a beam which contains a 1 kilo-ohm polysilicon piezoresistor 34. The total area of the three axis system was 4 square millimeters. Substantially better performance is expected to be realized with an integrated CMOS amplifier than an off chip amplified accelerometer.
With no external loading, the structures shown in Figure 6 could stand on their own held in place by aluminum hinges 40a-c. A micromanipulator or other external force is used to bend
the hinges into the desired position. Rotated structures such as shown in Figure 6 can be mad with interlocking braces to keep the structure in the desired position by technique similar t those used with polysilicon structures as described by Pister, "Hinged Polysilicon Structure with Integrated Thin Film Transistors, " in Proc. IEEE Solid State Sensor and Actuato Workshop, Hiltonhead, South Carolina, June 22-25, 1992, at 136-39. Mass assembly of device as shown in Figure 6 can be achieved with the assistance of scanning electro microscopes. A beam of high energy electrons are used to deposit a specific amount of charg on an electrically isolated structure to electrostatically bend the hinges so that the structur assumes the final configuration. A wide variety of sensors and actuators have previously been demonstrated usin simple post-processing of standard CMOS technology. According to the invention, it is als now possible to assemble simple three-dimensional structures and integral piezoresistiv deflection for sensors. Additionally, a simple new gas-phase approach to CMOS proces etching can be used to fabricate the micromachined structures. With this extensive set o microelectromechanical elements, coupled with a tremendous library of electrical capabilitie available in CMOS technologies, it is possible to design and fabricate sophisticated systems in wide variety of applications with very rapid turnaround time.
The hinged piezoresistive three-dimensional sensor or accelerometer of the illustrate embodiement can find applications immediately in many devices including but not limited to profilometer, an anemometer, magnetometer, hygrometer, electron tunneling sensors, and i cases where sensitivity is high enough in gyroscopic equipment. Other applications where suc devices can be anticipated as having immediate application automotive crash sensing wher requirements of 1 kHz bandwidth and +/-50 g range sensitivity is needed and disk drive shoc sensing, in smart packages and in sporting equipment. A new system has been developed which etches silicon highly selectively at moderat temperatures and without hydrodynamic forces potentially damaging to small structures an features. The system is based on the use of the gas phase etchant xenon diflouride, which is a unremarkable white solid at standard temperature and pressure.
11
Aluminum hinges and polysilicon piezoresistors have been fabricated using a standard commercial CMOS process with one maskless post-processing step. The hinges and piezoresistors have been formed using the metal interconnect and transistor gate layers with CMOS processes. Surface machining with xenon diflouride (XeF2) is a simple and effective alternative to standard bulk etchings for this process because of its extreme selectivity and gentle gas-phase etch. Xenon diflouride has been synthesized since the early 1960's and is commercially available.
The use of xenon difluoride is different from the prior art in three major ways. The most significant of which is the highly selective nature of the etch. Semiconductor processing requires a great deal of etching done with as much selectivity and control as possible to produce useful patterns and structures. Xenon diflouride etches silicon preferentially over almost all tested materials which one could encounter in semiconductor processing.
The second highly distinct feature of xenon diflouride is the gas phase nature of the etch. Gas phase etching allows for very gentle processing with no hydrodynamic forces. This gentle processing allows for the construction of thin oxide and metal structures by established processes which would otherwise be totally inaccessible using liquid phase etchants. Hydrodynamic forces in the liquid phase could damage even the grossest of such structures or at least many of the structures described here.
Lastly the process is run without externally input heat. Although there may be some slight heat output from the actual etching itself the fact that the processing is done in a low temperature environment allows for silicon etching masked by uncured photoresist or other low temperature materials.
The problem which prompted development of this technique was the fabrication of micromechanical structures with integrated electronics. No other currently available technique allows for the use of standard CMOS to build satisfactory micromechanical structures with integrated electronics.
This technique was originally conceived as a way to selectively etch silicon from standard CMOS technology chips to create microelectromechanical devices. In order to do this
12
we needed a highly selective, but minimally damaging system for etching silicon. Xeno diflouride had previously been used to etch the silicon away from the back side of a aluminum-silicon dioxide interface.
The illustrated embodiment is shown in the context of a piezoresistive acceleromete but it is to be specifically understood that any type of MEM device could be made consiste with the teachings of the invention.
When the chips return from the foundry, they require a single unmasked etch f finishing prior to die separation. The traditional EDP etch is useful for etching pits in structure with dimensions on the order of 100 microns, but for longer etches, the aluminum metalizatio in the bonding pads is destroyed. Hydrazene monohydrate has been proposed as a mor selective etchant but the health hazards of this material are substantially worse than EDP, whic itself is a fairly toxic substance.
According to the invention xenon difluoride and tetramethyl ammonium hydroxide hav been developed as extremely effective etchants for MEMS applications. One apparatus 10 f using the etchant is shown in Figure 7 where a chamber 12 connected by a valve 16 to a sourc 18 of xenon diflouride. Gas or nitrogen purging is also provided to chamber 12 through valv 20. Once chamber 12, with samples inside, has been pumped down to a moderate vacuum b pump 14, valve 16 is opened and small amounts of xenon diflouride vaporize in the lo pressure and enter the vessel. The etch is performed in vapor phase at room temperature wit no external energy sources at a partial pressure of 1-4 Torr. Under these conditions, etch rat as high as 10 microns per minute have been observed with 1 to 3 microns per minute bein typical. The etch is isotropic and independent of silicon doping compounds as well as highl selective.
This system has been used to etch a number of CMOS chips containing MOSFETs an other circuit elements, all of which were unaffected. Not only are aluminum and oxide pro against this etch, and thus candidates for masking, but photoresist and other polymer coatin also work as well. Unfortunately the gas phase etchant does attack chromium so certain for of stainless steel must be avoided in the design of chamber 12. Inconel, monel, and other suc
alloys designed for use in fluorine based etching systems may be used, however, and no problems have been encountered from a system designed using components derived from commercial reactive ion etching systems.
In addition to its highly selective and CMOS compatible nature this etching system introduces no hydrodynamic forces. It has been used by us to release microscopic mechanical structures hooked directly into accompanying electronics. The gentle nature of this etching system allows the researchers to etch silicon out from underneath silicon dioxide or metal hinges only a few microns wide and hundreds of microns long. This technique of etching allows for the construction of complicated micromechanical structures directly integrated on chip with analog and digital electronics; all at relatively low cost as the CMOS technological infrastructure is well established.
The extreme selectivity of xenon difluoride to silicon dioxide and silicon nitride has previously been known, D. E. Ibbotson et al., "Comparison of Xenon Difluoride in F-Atom Reactions with Silicon and Silicon Dioxide, " Appl. Physics Phys. Lett. 44(12):1 129-31 (1984), and H.F. Winters et al., "The Etching of Silicon with Xenon Difluoride Vapor, " Applied Physics Letters 34(1): 70-3 (1979). For example, 40 nanometer gate oxide is sufficient to protect the polysilicon gate from underside etch. We have also shown that xenon difluoride is extremely selectively to aluminum and photoresist. Simple mask test structure is made from 50 nanometer thick aluminum have been successfully released. A single layer of hard baked photoresist makes excellent etched mask. Chips bonded in standard ceramic chip carriers have been etched and tested successfully.
Silicon doping of tetramethyl ammonia hydroxide (TMAH) solutions have also been demonstrated as a method for improving the selectivity of TMAH to aluminum. C U Schnakenberg et al, "TMAH W Etchants for Silicon Micromachining, " in Proc. 6th Int. Conf. on Solid State Sensors and Actuators (Transducers '91) San Francisco, June 1991 at 815-18. By adding silicic acid directly, we have seen similar results. Cantilevered or end structure such as shown in Figure 8 have been produced using an etch solution of 80 milliliters of 25 percent TMAH, 16 grams of silicic acid, and balanced deionized water in a 250 milliliter beaker. The
chip was etched at 70 degrees for 24 hours, with the resulting etch depth of between 50 to 1 microns varying upon the surface pattern.
As can be seen from Figure 8, the etch is nearly isotropic. The primary differen between structures etched in liquid TMAH silicic acid solutions and structures etched in g phase xenon difluoride is the drying induced bending of the support beams.
Consider for example the use of the disclosed etchants for the fabrication of aluminum hinge and a polysilicon strain gauge. The aluminum hinge acts as a plastical deformable flexural hinge similar in function to the polyimide hinges described by Suzuki al., "Creation of an Insect Base Microrobot with an External Skeleton and Elastic Joints, " Proc. IEEE Microelectronic Mechanical Systems Workshop, Travemunde, Germany, Februa 4-7, 1992 at 190-95. The hinge is created by running a line of metal over bare silicon. T strain gauge is comprised of a polysilicon resistor protected from the etchant by surroundi oxides. A typical CMOS process will have an additional layer of metal and polysilicon shown in Figure 9 which is a simplified cross section of aluminum trace 22 running betwe oxide plates 24 and a contacting polysilicon piezoresistor 26.
The oxide and first metal over-etch into silicon substrate 28 causes aluminum trace 22 be lower than oxides 24. In a two or more metal process, all of the metal layers can be used make hinges, separately or in combination. Similarly, much of the silicon substrate in the op areas is removed by the over-etch of the oxide and metal layers, resulting in metal traces whi are recessed into the substrate after fabrication as shown in Figure 9.
Once the structure has been etched, the oxide plates and aluminum hinges will suspended over silicon pits. The multilayer structures are generally surprisingly fl considering the heterogeneity of the thin films. Strain gradient induced deflections are typica less than 10 microns for cantilevers with lengths less than 300 microns. On a recent r however, the tip deflection of a 300-micron oxide cantilever was over 100 microns. General this excessive curvature is undesirable.
The resistance of loops of aluminum as shown in Figure 8 is between 1 and 2 oh before and after the etch. Aluminum can be deformed elastically over small range of moti
15
and thereafter deforms plastically. Hinges are rotated using mechanical probes and can be rotated well past 90 degrees. The resistance of the plastically deformed aluminum lines also remains constant at between 1 to 2 ohms even after several deformations. Aluminum lines fail at current densities above 10 microamps per square micron before and after the etch. An accelerometer is comprised of a proof mass and a force detection system. Existing silicon micromachined accelerometers are typically made from custom bulk micromachining processes which are designed to yield proof masses in the order of magnitude of milligrams. High performance accelerometers are typically either used for capacity of position sensing or force feedback sensing. Virtually all accelerometers use off-chip electronics to detect a condition the measured electrical signal.
The etchants of the invention, and in particular, xenon difluoride are particularly advantageous when used to fabricate microelectromechanical devices using a polymer layer. Traditionally it has been difficult to integrate polymer layers into MEMS processes because of the tendancy of bulk and surface etchants to destroy the polymers. Because of the extreme selectivity of xenon difluoride, uses of many if not most of these polymers should now be possible.
It should now be readily appreciated that the advantages of the invention is that surface micromachining techniques instead of bulk techniques can be used, that piezoresistive sensing instead of capacitive sensing will be possible, that integrated circuits instead of off-chip electronics can be integrally fabricated with the sensing device, and that the entire device can be made from standard CMOS or equivalently substitutable technologies instead of requiring a customized fabrication technique or processes.
Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims.
The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings,
but to include by special definition in this specification structure, material or acts beyond t scope of the commonly defined meanings. Thus if an element can be understood in the conte of this specification as including more than one meaning, then its use in a claim must understood as being generic to all possible meanings supported by the specification and by t word itself.
The definitions of the words or elements of the following claims are, therefore, defin in this specification to include not only the combination of elements which are literally forth, but all equivalent structure, material or acts for performing substantially the sa function in substantially the same way to obtain substantially the same result. In addition to the equivalents of the claimed elements, obvious substitutions now or lat known to one with ordinary skill in the art are defined to be within the scope of the defin elements.
The claims are thus to be understood to include what is specifically illustrated a described above, what is conceptionally equivalent, what can be obviously substituted and al what essentially incorporates the essential idea of the invention.
Claims
1. In a method for fabricating microelectromechanical (MEM) devices, an improvement comprising:
providing a substantially completed MEM device through standard IC processing except for the need of at least one unmasked etch to complete said device; and
etching said MEM device with a generally isotropic etchant selected from the group of noble gas flourides and tetramethyl ammonium hydroxide.
2. The improvement of Claim 1 wherein etching said MEM device is performed with a gas phase xenon difluoride.
3. The improvement of Claim 2 wherein etching said MEM device is at ambient temperature without external heating.
4. The improvement of Claim 3 wherein etching said MEM device is performed under a partial vacuum.
5. The improvement of Claim 1 wherein etching said MEM device is performed in a aqueous solution of tetramethyl ammonium hydroxide with silicic acid.
6. In a method for fabricating microelectromechanical (MEM) devices, an improvement comprising:
providing a substantially completed MEM device except for the need of a single unmasked etch to complete said device; and
etching said MEM device with xenon difluoride in a gas phase.
7. A microelectromechanical (MEM) accelerometer defined in a semiconductor substrate comprising:
a proof mass fabricated from said substrate using integrated circuit processes;
at least one beam coupling said proof mass to said substrate, said beam being at least in part unsupported and extending from said proof mass to said substrate; and
at least one polysilicon piezoresistor disposed in said beam,
whereby said MEM accelerometer is inexpensively manufactured using standard integrated circuit technology.
8. The accelerometer of Claim 7 further comprising at least two unsupported beams coupling said proof mass to said substrate, each of said beams having at least one polysilicon piezoresistor disposed therein.
9. The accelerometer of Claim 7 wherein said substrate is generally planar and further comprising a hinge which is deformed so that said proof mass is oriented in a predetermined position out of the plane of said substrate.
10. The accelerometer of Claim 9 further comprising:
at least three of said proof masses fabricated from said substrate using integrated circuit processes;
at least three hinges, each of said hinges coupling one of said three proof masses to said substrate,
at least three beams coupled to corresponding ones of said three hinges, each of said beams being at least in part unsupported and extending from said proof mass to said substrate; and
at least three polysilicon piezoresistors, one of three polysilicon piezoresistors being disposed in each of said three beams,
wherein said proof masses are each oriented in a different plane relative to said substrate so that a three-axis accelerometer is provided.
11. The accelerometer of Claim 7 wherein said hinges are comprised of aluminum.
12. The accelerometer of Claim 11 wherein said beams are fabricated using xenon difluoride as a gas-phase ambient temperature etchant to define said beams apart from said substrate and proof mass.
13. The accelerometer of Claim 11 wherein said beams are fabricated using a tetramethyl ammonium hydroxide aqueous solution with silicic acid to define said beams apart from said substrate and proof mass.
14. The accelerometer of Claim 7 wherein said proof mass and polysilicon piezoresistor are formed using CMOS processes.
15. The accelerometer of Claim 14 wherein said beams are fabricated using xenon difluoride as a gas-phase ambient temperature etchant to define said beams apart from said substrate and proof mass.
16. The MEMS device of Claim 14 wherein said beam is defined and separated from said substrate through use of solution of tetramethyl ammonium hydroxide in silicic acid.
17. The MEMS device of Claim 9 wherein said proof mass, hinge and polysilicon piezoresistor are formed using CMOS processes.
18. In a method for fabricating microelectromechanical (MEM) devices, an improvement comprising:
providing a substantially completed MEM device except for the need of a single unmasked etch to complete said device; and 5 etching said MEM device with a substantially isotropic etchant selected from
6 the group of xenon difluoride and an aqueous solution of tetramethyl ammonium
7 hydroxide and silicic acid.
1 19. In a method for fabricating microelectromechanical (MEM)
2 devices, an improvement comprising:
3 providing a substantially completed MEM CMOS device except for the need
4 of at least one unmasked etch to complete said device; and
5 etching said MEM CMOS device with a generally isotropic etchant selected
6 from the group of xenon difluoride and tetramethyl ammonium hydroxide.
1 20. The improvement of Claim 19 wherein said substantially
2 completed MEM CMOS device is an accelerometer having an integrated circuit
3 substrate, a proof mass and a piezoresistive sensing element coupling said substrate to
4 said proof mass, but remaining undefined from them, wherein said etching defines
5 said sensing element by a single etch step by said generally isotropic etchant.
l
21. In a method of mass fabricating a microelectromechanical device,
"> an improvement comprising:
3 providing a device having portions which must be oriented to predetermined
4 three dimensional positions in order assume a final configuration for said device,
5 selected portions of said device having electrically isolated structures for receiving
6 and holding charge for at least a temporary period; and selectively depositing selected amounts of electric charge on said electrically isolated structures to generate electrostatic forces therebetween to move selected portions of said device to assume said final configuration.
22. The improvement of Claim 21 where selectively depositing selected amounts of electric charge on said electrically isolated structures is performed by selective control of a scanning electron microscope which is directed to deposit electron charges on said electrically isolated structures.
23. An improvement in a microelectromechanical (MEM) device having a substrate and a movable part separate from said substrate comprising a conductive derformable hinge coupling said substrate and part.
24. The improvement of claim 23 wherein said hinge is deformed so that said substrate and separate part form a three dimensional structure.
1 25. The improvement of claim 24 further comprising a sensing means for generating a position signal indicative of the spatial orientation of said part.
ι
26. The improvement of claim 24 further comprising force means disposed on said substrate and part for deforming said hinge to form said three
3 dimensional structure.
27. The improvement of claim 25 further comprising circuit means disposed on said substrate or part and coupled to said sensing means for processing said position signal.
28. The improvement of claim 23 wherein said part is interacts with electromagnetic radiation.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/379,751 US5726480A (en) | 1995-01-27 | 1995-01-27 | Etchants for use in micromachining of CMOS Microaccelerometers and microelectromechanical devices and method of making the same |
US08/379,751 | 1995-01-27 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1996023229A1 true WO1996023229A1 (en) | 1996-08-01 |
WO1996023229A9 WO1996023229A9 (en) | 1996-10-17 |
Family
ID=23498532
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1996/001343 WO1996023229A1 (en) | 1995-01-27 | 1996-01-26 | Etchants for use in micromachining of cmos microaccelerometers and microelectromechanical devices and method of making the same |
Country Status (2)
Country | Link |
---|---|
US (1) | US5726480A (en) |
WO (1) | WO1996023229A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0870170A2 (en) * | 1995-12-24 | 1998-10-14 | Dan Haronian | Micro-electro-mechanics systems (mems) |
US5998816A (en) * | 1997-01-31 | 1999-12-07 | Mitsubishi Denki Kabushiki Kaisha | Sensor element with removal resistance region |
US6355181B1 (en) | 1998-03-20 | 2002-03-12 | Surface Technology Systems Plc | Method and apparatus for manufacturing a micromechanical device |
US6409876B1 (en) | 1997-05-13 | 2002-06-25 | Surface Technology Systems, Plc | Apparatus for etching a workpiece |
US7670203B2 (en) * | 2000-08-30 | 2010-03-02 | Agere Systems Inc. | Process for making an on-chip vacuum tube device |
Families Citing this family (221)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6674562B1 (en) * | 1994-05-05 | 2004-01-06 | Iridigm Display Corporation | Interferometric modulation of radiation |
US20010003487A1 (en) * | 1996-11-05 | 2001-06-14 | Mark W. Miles | Visible spectrum modulator arrays |
US7297471B1 (en) * | 2003-04-15 | 2007-11-20 | Idc, Llc | Method for manufacturing an array of interferometric modulators |
US6680792B2 (en) * | 1994-05-05 | 2004-01-20 | Iridigm Display Corporation | Interferometric modulation of radiation |
US8014059B2 (en) * | 1994-05-05 | 2011-09-06 | Qualcomm Mems Technologies, Inc. | System and method for charge control in a MEMS device |
US7123216B1 (en) * | 1994-05-05 | 2006-10-17 | Idc, Llc | Photonic MEMS and structures |
US6710908B2 (en) | 1994-05-05 | 2004-03-23 | Iridigm Display Corporation | Controlling micro-electro-mechanical cavities |
US7550794B2 (en) * | 2002-09-20 | 2009-06-23 | Idc, Llc | Micromechanical systems device comprising a displaceable electrode and a charge-trapping layer |
US7898722B2 (en) * | 1995-05-01 | 2011-03-01 | Qualcomm Mems Technologies, Inc. | Microelectromechanical device with restoring electrode |
US6969635B2 (en) * | 2000-12-07 | 2005-11-29 | Reflectivity, Inc. | Methods for depositing, releasing and packaging micro-electromechanical devices on wafer substrates |
US6849471B2 (en) | 2003-03-28 | 2005-02-01 | Reflectivity, Inc. | Barrier layers for microelectromechanical systems |
US5942791A (en) * | 1996-03-06 | 1999-08-24 | Gec-Marconi Limited | Micromachined devices having microbridge structure |
US7929197B2 (en) * | 1996-11-05 | 2011-04-19 | Qualcomm Mems Technologies, Inc. | System and method for a MEMS device |
US7830588B2 (en) * | 1996-12-19 | 2010-11-09 | Qualcomm Mems Technologies, Inc. | Method of making a light modulating display device and associated transistor circuitry and structures thereof |
CH691559A5 (en) * | 1997-04-21 | 2001-08-15 | Asulab Sa | magnetic micro-switch and its production process. |
US5912094A (en) * | 1997-05-15 | 1999-06-15 | Lucent Technologies, Inc. | Method and apparatus for making a micro device |
US5955771A (en) * | 1997-11-12 | 1999-09-21 | Kulite Semiconductor Products, Inc. | Sensors for use in high vibrational applications and methods for fabricating same |
US8928967B2 (en) | 1998-04-08 | 2015-01-06 | Qualcomm Mems Technologies, Inc. | Method and device for modulating light |
KR100703140B1 (en) * | 1998-04-08 | 2007-04-05 | 이리다임 디스플레이 코포레이션 | Interferometric modulation and its manufacturing method |
US6303986B1 (en) | 1998-07-29 | 2001-10-16 | Silicon Light Machines | Method of and apparatus for sealing an hermetic lid to a semiconductor die |
US6350657B1 (en) * | 1998-08-03 | 2002-02-26 | Stmicroelectronics S.R.L. | Inexpensive method of manufacturing an SOI wafer |
JP2000091818A (en) * | 1998-09-11 | 2000-03-31 | Toyota Motor Corp | Manufacture of film-type transmission line and method for connecting the same line |
US6261494B1 (en) * | 1998-10-22 | 2001-07-17 | Northeastern University | Method of forming plastically deformable microstructures |
US6618217B2 (en) * | 1999-02-23 | 2003-09-09 | Texas Instruments Incorporated | System and method for determining the position of a device |
JP4270647B2 (en) | 1999-05-31 | 2009-06-03 | ボールセミコンダクター株式会社 | Inclinometer |
JP4316050B2 (en) | 1999-05-31 | 2009-08-19 | ボールセミコンダクター株式会社 | Micromachine manufacturing method |
US6057520A (en) * | 1999-06-30 | 2000-05-02 | Mcnc | Arc resistant high voltage micromachined electrostatic switch |
US6229683B1 (en) | 1999-06-30 | 2001-05-08 | Mcnc | High voltage micromachined electrostatic switch |
WO2003007049A1 (en) * | 1999-10-05 | 2003-01-23 | Iridigm Display Corporation | Photonic mems and structures |
US7041224B2 (en) * | 1999-10-26 | 2006-05-09 | Reflectivity, Inc. | Method for vapor phase etching of silicon |
US6290864B1 (en) | 1999-10-26 | 2001-09-18 | Reflectivity, Inc. | Fluoride gas etching of silicon with improved selectivity |
US6942811B2 (en) * | 1999-10-26 | 2005-09-13 | Reflectivity, Inc | Method for achieving improved selectivity in an etching process |
US6949202B1 (en) | 1999-10-26 | 2005-09-27 | Reflectivity, Inc | Apparatus and method for flow of process gas in an ultra-clean environment |
US6960305B2 (en) * | 1999-10-26 | 2005-11-01 | Reflectivity, Inc | Methods for forming and releasing microelectromechanical structures |
US6359374B1 (en) | 1999-11-23 | 2002-03-19 | Mcnc | Miniature electrical relays using a piezoelectric thin film as an actuating element |
US6197610B1 (en) | 2000-01-14 | 2001-03-06 | Ball Semiconductor, Inc. | Method of making small gaps for small electrical/mechanical devices |
US6444135B1 (en) | 2000-01-14 | 2002-09-03 | Ball Semiconductor, Inc. | Method to make gas permeable shell for MEMS devices with controlled porosity |
US20020132113A1 (en) * | 2000-01-14 | 2002-09-19 | Ball Semiconductor, Inc. | Method and system for making a micromachine device with a gas permeable enclosure |
US6521477B1 (en) * | 2000-02-02 | 2003-02-18 | Raytheon Company | Vacuum package fabrication of integrated circuit components |
US6479320B1 (en) | 2000-02-02 | 2002-11-12 | Raytheon Company | Vacuum package fabrication of microelectromechanical system devices with integrated circuit components |
US7010332B1 (en) | 2000-02-21 | 2006-03-07 | Telefonaktiebolaget Lm Ericsson(Publ) | Wireless headset with automatic power control |
US6500356B2 (en) * | 2000-03-27 | 2002-12-31 | Applied Materials, Inc. | Selectively etching silicon using fluorine without plasma |
US20030010354A1 (en) * | 2000-03-27 | 2003-01-16 | Applied Materials, Inc. | Fluorine process for cleaning semiconductor process chamber |
US6690014B1 (en) | 2000-04-25 | 2004-02-10 | Raytheon Company | Microbolometer and method for forming |
US7019376B2 (en) * | 2000-08-11 | 2006-03-28 | Reflectivity, Inc | Micromirror array device with a small pitch size |
US6708491B1 (en) | 2000-09-12 | 2004-03-23 | 3M Innovative Properties Company | Direct acting vertical thermal actuator |
US6483419B1 (en) * | 2000-09-12 | 2002-11-19 | 3M Innovative Properties Company | Combination horizontal and vertical thermal actuator |
US6531947B1 (en) * | 2000-09-12 | 2003-03-11 | 3M Innovative Properties Company | Direct acting vertical thermal actuator with controlled bending |
US6887337B2 (en) | 2000-09-19 | 2005-05-03 | Xactix, Inc. | Apparatus for etching semiconductor samples and a source for providing a gas by sublimation thereto |
US6576556B2 (en) | 2000-09-21 | 2003-06-10 | Mitsubishi Denki Kabushiki Kaisha | Method of manufacturing semiconductor device and method of manufacturing infrared image sensor |
US6908793B2 (en) | 2000-11-22 | 2005-06-21 | The Johns Hopkins University | Method for fabricating a semiconductor device |
US6707591B2 (en) | 2001-04-10 | 2004-03-16 | Silicon Light Machines | Angled illumination for a single order light modulator based projection system |
US6777681B1 (en) | 2001-04-25 | 2004-08-17 | Raytheon Company | Infrared detector with amorphous silicon detector elements, and a method of making it |
AU2002303842A1 (en) * | 2001-05-22 | 2002-12-03 | Reflectivity, Inc. | A method for making a micromechanical device by removing a sacrificial layer with multiple sequential etchants |
US6747781B2 (en) | 2001-06-25 | 2004-06-08 | Silicon Light Machines, Inc. | Method, apparatus, and diffuser for reducing laser speckle |
US6782205B2 (en) | 2001-06-25 | 2004-08-24 | Silicon Light Machines | Method and apparatus for dynamic equalization in wavelength division multiplexing |
US6632698B2 (en) * | 2001-08-07 | 2003-10-14 | Hewlett-Packard Development Company, L.P. | Microelectromechanical device having a stiffened support beam, and methods of forming stiffened support beams in MEMS |
US6829092B2 (en) | 2001-08-15 | 2004-12-07 | Silicon Light Machines, Inc. | Blazed grating light valve |
WO2003027002A2 (en) * | 2001-09-01 | 2003-04-03 | Robert Bosch Gmbh | Method for the production of a micromechanical structure |
US6930364B2 (en) * | 2001-09-13 | 2005-08-16 | Silicon Light Machines Corporation | Microelectronic mechanical system and methods |
US7189332B2 (en) * | 2001-09-17 | 2007-03-13 | Texas Instruments Incorporated | Apparatus and method for detecting an endpoint in a vapor phase etch |
US6933933B2 (en) | 2001-10-02 | 2005-08-23 | Harris Corporation | Pen cartridge that transmits acceleration signal for recreating handwritten signatures and communications |
US20030073302A1 (en) * | 2001-10-12 | 2003-04-17 | Reflectivity, Inc., A California Corporation | Methods for formation of air gap interconnects |
US7009180B2 (en) * | 2001-12-14 | 2006-03-07 | Optiscan Biomedical Corp. | Pathlength-independent methods for optically determining material composition |
US6800238B1 (en) | 2002-01-15 | 2004-10-05 | Silicon Light Machines, Inc. | Method for domain patterning in low coercive field ferroelectrics |
US6835616B1 (en) | 2002-01-29 | 2004-12-28 | Cypress Semiconductor Corporation | Method of forming a floating metal structure in an integrated circuit |
US7026235B1 (en) | 2002-02-07 | 2006-04-11 | Cypress Semiconductor Corporation | Dual-damascene process and associated floating metal structures |
US6794119B2 (en) * | 2002-02-12 | 2004-09-21 | Iridigm Display Corporation | Method for fabricating a structure for a microelectromechanical systems (MEMS) device |
US6574033B1 (en) | 2002-02-27 | 2003-06-03 | Iridigm Display Corporation | Microelectromechanical systems device and method for fabricating same |
US7027200B2 (en) * | 2002-03-22 | 2006-04-11 | Reflectivity, Inc | Etching method used in fabrications of microstructures |
US6965468B2 (en) * | 2003-07-03 | 2005-11-15 | Reflectivity, Inc | Micromirror array having reduced gap between adjacent micromirrors of the micromirror array |
US20030183916A1 (en) * | 2002-03-27 | 2003-10-02 | John Heck | Packaging microelectromechanical systems |
US6652644B1 (en) | 2002-03-29 | 2003-11-25 | Silicon Light Machines, Inc. | Adjusting lithium oxide concentration in wafers using a two-phase lithium-rich source |
US6893498B1 (en) | 2002-03-29 | 2005-05-17 | Silicon Light Machines Corporation | Method and apparatus for adjusting lithium oxide concentration in wafers |
US6808563B1 (en) | 2002-03-29 | 2004-10-26 | Silicon Light Machines Corporation | Controlled partial pressure technique for adjusting lithium oxide concentration in wafers |
KR100461787B1 (en) * | 2002-04-10 | 2004-12-14 | 학교법인 포항공과대학교 | Accelerometers using mems technology and method for manufacturing the same |
US6728023B1 (en) | 2002-05-28 | 2004-04-27 | Silicon Light Machines | Optical device arrays with optimized image resolution |
US6767751B2 (en) * | 2002-05-28 | 2004-07-27 | Silicon Light Machines, Inc. | Integrated driver process flow |
US6822797B1 (en) | 2002-05-31 | 2004-11-23 | Silicon Light Machines, Inc. | Light modulator structure for producing high-contrast operation using zero-order light |
US6829258B1 (en) | 2002-06-26 | 2004-12-07 | Silicon Light Machines, Inc. | Rapidly tunable external cavity laser |
US6777258B1 (en) | 2002-06-28 | 2004-08-17 | Silicon Light Machines, Inc. | Conductive etch stop for etching a sacrificial layer |
US6813059B2 (en) | 2002-06-28 | 2004-11-02 | Silicon Light Machines, Inc. | Reduced formation of asperities in contact micro-structures |
US6714337B1 (en) | 2002-06-28 | 2004-03-30 | Silicon Light Machines | Method and device for modulating a light beam and having an improved gamma response |
JP2004062938A (en) * | 2002-07-25 | 2004-02-26 | Pioneer Electronic Corp | Spherical aberration correcting device and spherical aberration correcting method |
TW593125B (en) * | 2002-08-09 | 2004-06-21 | Ind Tech Res Inst | MEMS type differential actuator |
US6801354B1 (en) | 2002-08-20 | 2004-10-05 | Silicon Light Machines, Inc. | 2-D diffraction grating for substantially eliminating polarization dependent losses |
US7781850B2 (en) * | 2002-09-20 | 2010-08-24 | Qualcomm Mems Technologies, Inc. | Controlling electromechanical behavior of structures within a microelectromechanical systems device |
US7803536B2 (en) | 2002-09-20 | 2010-09-28 | Integrated Dna Technologies, Inc. | Methods of detecting fluorescence with anthraquinone quencher dyes |
US6712480B1 (en) | 2002-09-27 | 2004-03-30 | Silicon Light Machines | Controlled curvature of stressed micro-structures |
US6810883B2 (en) * | 2002-11-08 | 2004-11-02 | Philip Morris Usa Inc. | Electrically heated cigarette smoking system with internal manifolding for puff detection |
US7105361B2 (en) * | 2003-01-06 | 2006-09-12 | Applied Materials, Inc. | Method of etching a magnetic material |
US6806997B1 (en) | 2003-02-28 | 2004-10-19 | Silicon Light Machines, Inc. | Patterned diffractive light modulator ribbon for PDL reduction |
US6829077B1 (en) | 2003-02-28 | 2004-12-07 | Silicon Light Machines, Inc. | Diffractive light modulator with dynamically rotatable diffraction plane |
US6913942B2 (en) | 2003-03-28 | 2005-07-05 | Reflectvity, Inc | Sacrificial layers for use in fabrications of microelectromechanical devices |
WO2004089814A2 (en) * | 2003-04-08 | 2004-10-21 | Bookham Technology Plc | Thermal actuator |
TW594360B (en) * | 2003-04-21 | 2004-06-21 | Prime View Int Corp Ltd | A method for fabricating an interference display cell |
US7005193B2 (en) * | 2003-04-29 | 2006-02-28 | Motorola, Inc. | Method of adding mass to MEMS structures |
TW570896B (en) | 2003-05-26 | 2004-01-11 | Prime View Int Co Ltd | A method for fabricating an interference display cell |
TW589752B (en) * | 2003-05-28 | 2004-06-01 | Au Optronics Corp | Semiconductor acceleration sensor |
WO2005001422A2 (en) * | 2003-06-06 | 2005-01-06 | The Board Of Trustees Of The University Of Illinois | Sensor chip and apparatus for tactile and/or flow |
US6927146B2 (en) * | 2003-06-17 | 2005-08-09 | Intel Corporation | Chemical thinning of epitaxial silicon layer over buried oxide |
US7221495B2 (en) * | 2003-06-24 | 2007-05-22 | Idc Llc | Thin film precursor stack for MEMS manufacturing |
US6980347B2 (en) * | 2003-07-03 | 2005-12-27 | Reflectivity, Inc | Micromirror having reduced space between hinge and mirror plate of the micromirror |
JP4247554B2 (en) * | 2003-07-30 | 2009-04-02 | 独立行政法人理化学研究所 | Mechanochemical sensor |
TW200506479A (en) * | 2003-08-15 | 2005-02-16 | Prime View Int Co Ltd | Color changeable pixel for an interference display |
TWI231865B (en) * | 2003-08-26 | 2005-05-01 | Prime View Int Co Ltd | An interference display cell and fabrication method thereof |
US7094622B1 (en) | 2003-08-27 | 2006-08-22 | Louisiana Tech University Foundation, Inc. | Polymer based tunneling sensor |
TWI232333B (en) * | 2003-09-03 | 2005-05-11 | Prime View Int Co Ltd | Display unit using interferometric modulation and manufacturing method thereof |
US6939472B2 (en) * | 2003-09-17 | 2005-09-06 | Reflectivity, Inc. | Etching method in fabrications of microstructures |
US7645704B2 (en) * | 2003-09-17 | 2010-01-12 | Texas Instruments Incorporated | Methods and apparatus of etch process control in fabrications of microstructures |
US7161728B2 (en) * | 2003-12-09 | 2007-01-09 | Idc, Llc | Area array modulation and lead reduction in interferometric modulators |
US7532194B2 (en) * | 2004-02-03 | 2009-05-12 | Idc, Llc | Driver voltage adjuster |
US7119945B2 (en) * | 2004-03-03 | 2006-10-10 | Idc, Llc | Altering temporal response of microelectromechanical elements |
US7706050B2 (en) * | 2004-03-05 | 2010-04-27 | Qualcomm Mems Technologies, Inc. | Integrated modulator illumination |
US7720148B2 (en) * | 2004-03-26 | 2010-05-18 | The Hong Kong University Of Science And Technology | Efficient multi-frame motion estimation for video compression |
US7476327B2 (en) * | 2004-05-04 | 2009-01-13 | Idc, Llc | Method of manufacture for microelectromechanical devices |
US7644624B2 (en) | 2004-06-04 | 2010-01-12 | The Board Of Trustees Of The University Of Illinois | Artificial lateral line |
GB0413554D0 (en) * | 2004-06-17 | 2004-07-21 | Point 35 Microstructures Ltd | Improved method and apparartus for the etching of microstructures |
US7256922B2 (en) * | 2004-07-02 | 2007-08-14 | Idc, Llc | Interferometric modulators with thin film transistors |
TWI233916B (en) * | 2004-07-09 | 2005-06-11 | Prime View Int Co Ltd | A structure of a micro electro mechanical system |
EP1855142A3 (en) * | 2004-07-29 | 2008-07-30 | Idc, Llc | System and method for micro-electromechanical operating of an interferometric modulator |
US7684104B2 (en) * | 2004-09-27 | 2010-03-23 | Idc, Llc | MEMS using filler material and method |
US20060067650A1 (en) * | 2004-09-27 | 2006-03-30 | Clarence Chui | Method of making a reflective display device using thin film transistor production techniques |
US20060065622A1 (en) * | 2004-09-27 | 2006-03-30 | Floyd Philip D | Method and system for xenon fluoride etching with enhanced efficiency |
US7553684B2 (en) * | 2004-09-27 | 2009-06-30 | Idc, Llc | Method of fabricating interferometric devices using lift-off processing techniques |
US7813026B2 (en) * | 2004-09-27 | 2010-10-12 | Qualcomm Mems Technologies, Inc. | System and method of reducing color shift in a display |
US7920135B2 (en) * | 2004-09-27 | 2011-04-05 | Qualcomm Mems Technologies, Inc. | Method and system for driving a bi-stable display |
US20060065366A1 (en) * | 2004-09-27 | 2006-03-30 | Cummings William J | Portable etch chamber |
US7719500B2 (en) * | 2004-09-27 | 2010-05-18 | Qualcomm Mems Technologies, Inc. | Reflective display pixels arranged in non-rectangular arrays |
US7369296B2 (en) * | 2004-09-27 | 2008-05-06 | Idc, Llc | Device and method for modifying actuation voltage thresholds of a deformable membrane in an interferometric modulator |
US7373026B2 (en) * | 2004-09-27 | 2008-05-13 | Idc, Llc | MEMS device fabricated on a pre-patterned substrate |
US7369294B2 (en) * | 2004-09-27 | 2008-05-06 | Idc, Llc | Ornamental display device |
US7372613B2 (en) | 2004-09-27 | 2008-05-13 | Idc, Llc | Method and device for multistate interferometric light modulation |
US7808703B2 (en) | 2004-09-27 | 2010-10-05 | Qualcomm Mems Technologies, Inc. | System and method for implementation of interferometric modulator displays |
US7535466B2 (en) * | 2004-09-27 | 2009-05-19 | Idc, Llc | System with server based control of client device display features |
US20060176241A1 (en) * | 2004-09-27 | 2006-08-10 | Sampsell Jeffrey B | System and method of transmitting video data |
US7586484B2 (en) * | 2004-09-27 | 2009-09-08 | Idc, Llc | Controller and driver features for bi-stable display |
US7554714B2 (en) * | 2004-09-27 | 2009-06-30 | Idc, Llc | Device and method for manipulation of thermal response in a modulator |
US7527995B2 (en) * | 2004-09-27 | 2009-05-05 | Qualcomm Mems Technologies, Inc. | Method of making prestructure for MEMS systems |
US7630119B2 (en) * | 2004-09-27 | 2009-12-08 | Qualcomm Mems Technologies, Inc. | Apparatus and method for reducing slippage between structures in an interferometric modulator |
US20060066596A1 (en) * | 2004-09-27 | 2006-03-30 | Sampsell Jeffrey B | System and method of transmitting video data |
US7653371B2 (en) * | 2004-09-27 | 2010-01-26 | Qualcomm Mems Technologies, Inc. | Selectable capacitance circuit |
US7893919B2 (en) | 2004-09-27 | 2011-02-22 | Qualcomm Mems Technologies, Inc. | Display region architectures |
US8008736B2 (en) * | 2004-09-27 | 2011-08-30 | Qualcomm Mems Technologies, Inc. | Analog interferometric modulator device |
US7492502B2 (en) * | 2004-09-27 | 2009-02-17 | Idc, Llc | Method of fabricating a free-standing microstructure |
US7321456B2 (en) * | 2004-09-27 | 2008-01-22 | Idc, Llc | Method and device for corner interferometric modulation |
US7460246B2 (en) * | 2004-09-27 | 2008-12-02 | Idc, Llc | Method and system for sensing light using interferometric elements |
US7420728B2 (en) * | 2004-09-27 | 2008-09-02 | Idc, Llc | Methods of fabricating interferometric modulators by selectively removing a material |
US7936497B2 (en) * | 2004-09-27 | 2011-05-03 | Qualcomm Mems Technologies, Inc. | MEMS device having deformable membrane characterized by mechanical persistence |
US7420725B2 (en) | 2004-09-27 | 2008-09-02 | Idc, Llc | Device having a conductive light absorbing mask and method for fabricating same |
US7417783B2 (en) * | 2004-09-27 | 2008-08-26 | Idc, Llc | Mirror and mirror layer for optical modulator and method |
US7349136B2 (en) * | 2004-09-27 | 2008-03-25 | Idc, Llc | Method and device for a display having transparent components integrated therein |
US7317568B2 (en) * | 2004-09-27 | 2008-01-08 | Idc, Llc | System and method of implementation of interferometric modulators for display mirrors |
US7405861B2 (en) * | 2004-09-27 | 2008-07-29 | Idc, Llc | Method and device for protecting interferometric modulators from electrostatic discharge |
US7944599B2 (en) | 2004-09-27 | 2011-05-17 | Qualcomm Mems Technologies, Inc. | Electromechanical device with optical function separated from mechanical and electrical function |
US7355780B2 (en) * | 2004-09-27 | 2008-04-08 | Idc, Llc | System and method of illuminating interferometric modulators using backlighting |
US7289259B2 (en) * | 2004-09-27 | 2007-10-30 | Idc, Llc | Conductive bus structure for interferometric modulator array |
US7304784B2 (en) * | 2004-09-27 | 2007-12-04 | Idc, Llc | Reflective display device having viewable display on both sides |
US7583429B2 (en) | 2004-09-27 | 2009-09-01 | Idc, Llc | Ornamental display device |
US7130104B2 (en) * | 2004-09-27 | 2006-10-31 | Idc, Llc | Methods and devices for inhibiting tilting of a mirror in an interferometric modulator |
US7302157B2 (en) * | 2004-09-27 | 2007-11-27 | Idc, Llc | System and method for multi-level brightness in interferometric modulation |
US7616013B2 (en) * | 2004-11-11 | 2009-11-10 | Brigham Young University | Micromechanical positional state sensing apparatus method and system |
US8109149B2 (en) | 2004-11-17 | 2012-02-07 | Lawrence Livermore National Security, Llc | Contact stress sensor |
US7311009B2 (en) * | 2004-11-17 | 2007-12-25 | Lawrence Livermore National Security, Llc | Microelectromechanical systems contact stress sensor |
TW200628877A (en) * | 2005-02-04 | 2006-08-16 | Prime View Int Co Ltd | Method of manufacturing optical interference type color display |
US7258010B2 (en) * | 2005-03-09 | 2007-08-21 | Honeywell International Inc. | MEMS device with thinned comb fingers |
WO2007013992A1 (en) * | 2005-07-22 | 2007-02-01 | Qualcomm Incorporated | Support structure for mems device and methods therefor |
EP2495212A3 (en) * | 2005-07-22 | 2012-10-31 | QUALCOMM MEMS Technologies, Inc. | Mems devices having support structures and methods of fabricating the same |
WO2007013939A1 (en) * | 2005-07-22 | 2007-02-01 | Qualcomm Incorporated | Support structure for mems device and methods therefor |
US7630114B2 (en) * | 2005-10-28 | 2009-12-08 | Idc, Llc | Diffusion barrier layer for MEMS devices |
US7795061B2 (en) | 2005-12-29 | 2010-09-14 | Qualcomm Mems Technologies, Inc. | Method of creating MEMS device cavities by a non-etching process |
US7916980B2 (en) | 2006-01-13 | 2011-03-29 | Qualcomm Mems Technologies, Inc. | Interconnect structure for MEMS device |
US7382515B2 (en) * | 2006-01-18 | 2008-06-03 | Qualcomm Mems Technologies, Inc. | Silicon-rich silicon nitrides as etch stops in MEMS manufacture |
US7459686B2 (en) * | 2006-01-26 | 2008-12-02 | L-3 Communications Corporation | Systems and methods for integrating focal plane arrays |
US7462831B2 (en) * | 2006-01-26 | 2008-12-09 | L-3 Communications Corporation | Systems and methods for bonding |
US7655909B2 (en) * | 2006-01-26 | 2010-02-02 | L-3 Communications Corporation | Infrared detector elements and methods of forming same |
US7582952B2 (en) * | 2006-02-21 | 2009-09-01 | Qualcomm Mems Technologies, Inc. | Method for providing and removing discharging interconnect for chip-on-glass output leads and structures thereof |
US7547568B2 (en) * | 2006-02-22 | 2009-06-16 | Qualcomm Mems Technologies, Inc. | Electrical conditioning of MEMS device and insulating layer thereof |
US7550810B2 (en) * | 2006-02-23 | 2009-06-23 | Qualcomm Mems Technologies, Inc. | MEMS device having a layer movable at asymmetric rates |
US7450295B2 (en) * | 2006-03-02 | 2008-11-11 | Qualcomm Mems Technologies, Inc. | Methods for producing MEMS with protective coatings using multi-component sacrificial layers |
US7903047B2 (en) * | 2006-04-17 | 2011-03-08 | Qualcomm Mems Technologies, Inc. | Mode indicator for interferometric modulator displays |
US7527996B2 (en) * | 2006-04-19 | 2009-05-05 | Qualcomm Mems Technologies, Inc. | Non-planar surface structures and process for microelectromechanical systems |
US20070249078A1 (en) * | 2006-04-19 | 2007-10-25 | Ming-Hau Tung | Non-planar surface structures and process for microelectromechanical systems |
US7417784B2 (en) * | 2006-04-19 | 2008-08-26 | Qualcomm Mems Technologies, Inc. | Microelectromechanical device and method utilizing a porous surface |
US7711239B2 (en) | 2006-04-19 | 2010-05-04 | Qualcomm Mems Technologies, Inc. | Microelectromechanical device and method utilizing nanoparticles |
US7369292B2 (en) * | 2006-05-03 | 2008-05-06 | Qualcomm Mems Technologies, Inc. | Electrode and interconnect materials for MEMS devices |
US7405863B2 (en) * | 2006-06-01 | 2008-07-29 | Qualcomm Mems Technologies, Inc. | Patterning of mechanical layer in MEMS to reduce stresses at supports |
US7649671B2 (en) * | 2006-06-01 | 2010-01-19 | Qualcomm Mems Technologies, Inc. | Analog interferometric modulator device with electrostatic actuation and release |
US7321457B2 (en) | 2006-06-01 | 2008-01-22 | Qualcomm Incorporated | Process and structure for fabrication of MEMS device having isolated edge posts |
AU2007293476B2 (en) | 2006-06-02 | 2011-07-07 | The Board Of Trustees Of The University Of Illinois | Soft mems |
US7661319B2 (en) * | 2006-06-02 | 2010-02-16 | The Board Of Trustees Of The University Of Illinois | Micromachined artificial haircell |
US7824943B2 (en) * | 2006-06-04 | 2010-11-02 | Akustica, Inc. | Methods for trapping charge in a microelectromechanical system and microelectromechanical system employing same |
US7471442B2 (en) * | 2006-06-15 | 2008-12-30 | Qualcomm Mems Technologies, Inc. | Method and apparatus for low range bit depth enhancements for MEMS display architectures |
US7835061B2 (en) * | 2006-06-28 | 2010-11-16 | Qualcomm Mems Technologies, Inc. | Support structures for free-standing electromechanical devices |
US7385744B2 (en) * | 2006-06-28 | 2008-06-10 | Qualcomm Mems Technologies, Inc. | Support structure for free-standing MEMS device and methods for forming the same |
US7527998B2 (en) * | 2006-06-30 | 2009-05-05 | Qualcomm Mems Technologies, Inc. | Method of manufacturing MEMS devices providing air gap control |
JP4327183B2 (en) * | 2006-07-31 | 2009-09-09 | 株式会社日立製作所 | High pressure fuel pump control device for internal combustion engine |
US7763546B2 (en) | 2006-08-02 | 2010-07-27 | Qualcomm Mems Technologies, Inc. | Methods for reducing surface charges during the manufacture of microelectromechanical systems devices |
US7566664B2 (en) * | 2006-08-02 | 2009-07-28 | Qualcomm Mems Technologies, Inc. | Selective etching of MEMS using gaseous halides and reactive co-etchants |
US7718965B1 (en) | 2006-08-03 | 2010-05-18 | L-3 Communications Corporation | Microbolometer infrared detector elements and methods for forming same |
US20080043315A1 (en) * | 2006-08-15 | 2008-02-21 | Cummings William J | High profile contacts for microelectromechanical systems |
US8153980B1 (en) | 2006-11-30 | 2012-04-10 | L-3 Communications Corp. | Color correction for radiation detectors |
US7733552B2 (en) * | 2007-03-21 | 2010-06-08 | Qualcomm Mems Technologies, Inc | MEMS cavity-coating layers and methods |
US7719752B2 (en) * | 2007-05-11 | 2010-05-18 | Qualcomm Mems Technologies, Inc. | MEMS structures, methods of fabricating MEMS components on separate substrates and assembly of same |
US7569488B2 (en) * | 2007-06-22 | 2009-08-04 | Qualcomm Mems Technologies, Inc. | Methods of making a MEMS device by monitoring a process parameter |
US7851239B2 (en) * | 2008-06-05 | 2010-12-14 | Qualcomm Mems Technologies, Inc. | Low temperature amorphous silicon sacrificial layer for controlled adhesion in MEMS devices |
US8187902B2 (en) * | 2008-07-09 | 2012-05-29 | The Charles Stark Draper Laboratory, Inc. | High performance sensors and methods for forming the same |
US7719754B2 (en) * | 2008-09-30 | 2010-05-18 | Qualcomm Mems Technologies, Inc. | Multi-thickness layers for MEMS and mask-saving sequence for same |
US7864403B2 (en) * | 2009-03-27 | 2011-01-04 | Qualcomm Mems Technologies, Inc. | Post-release adjustment of interferometric modulator reflectivity |
US8581679B2 (en) * | 2010-02-26 | 2013-11-12 | Stmicroelectronics Asia Pacific Pte. Ltd. | Switch with increased magnetic sensitivity |
KR20130100232A (en) | 2010-04-09 | 2013-09-10 | 퀄컴 엠이엠에스 테크놀로지스, 인크. | Mechanical layer of an electromechanical device and methods of forming the same |
CN101905857B (en) * | 2010-07-21 | 2012-07-25 | 中国科学院半导体研究所 | Method for preventing structural layer materials of MEMS (Micro-Electromechanical System) devices from being electrochemically corroded on large scale |
CN101905858B (en) * | 2010-07-21 | 2012-07-25 | 中国科学院半导体研究所 | Method for preventing MEMS (Micro-Electromechanical System) device structural layer material from being electrochemically corroded |
US8765514B1 (en) | 2010-11-12 | 2014-07-01 | L-3 Communications Corp. | Transitioned film growth for conductive semiconductor materials |
US8963159B2 (en) | 2011-04-04 | 2015-02-24 | Qualcomm Mems Technologies, Inc. | Pixel via and methods of forming the same |
US9134527B2 (en) | 2011-04-04 | 2015-09-15 | Qualcomm Mems Technologies, Inc. | Pixel via and methods of forming the same |
US8659816B2 (en) | 2011-04-25 | 2014-02-25 | Qualcomm Mems Technologies, Inc. | Mechanical layer and methods of making the same |
US9091647B2 (en) * | 2012-09-08 | 2015-07-28 | Taiwan Semiconductor Manufacturing Company, Ltd. | Direct sensing bioFETs and methods of manufacture |
EP2966454B1 (en) * | 2014-07-07 | 2017-08-30 | EM Microelectronic-Marin SA | Method for measuring a physical parameter, and electronic circuit for implementing same |
US9927786B2 (en) | 2014-10-02 | 2018-03-27 | Anne Dewitte | Expandable and collapsible shape element for a programmable shape surface |
EP3904846A1 (en) * | 2020-04-29 | 2021-11-03 | Infineon Technologies AG | Thermal emitter with embedded heating element |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4945773A (en) * | 1989-03-06 | 1990-08-07 | Ford Motor Company | Force transducer etched from silicon |
US5357803A (en) * | 1992-04-08 | 1994-10-25 | Rochester Institute Of Technology | Micromachined microaccelerometer for measuring acceleration along three axes |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4487677A (en) * | 1983-04-11 | 1984-12-11 | Metals Production Research, Inc. | Electrolytic recovery system for obtaining titanium metal from its ore |
US5354416A (en) * | 1986-09-05 | 1994-10-11 | Sadayuki Okudaira | Dry etching method |
US4765865A (en) * | 1987-05-04 | 1988-08-23 | Ford Motor Company | Silicon etch rate enhancement |
US4893509A (en) * | 1988-12-27 | 1990-01-16 | General Motors Corporation | Method and product for fabricating a resonant-bridge microaccelerometer |
US4930043A (en) * | 1989-02-28 | 1990-05-29 | United Technologies | Closed-loop capacitive accelerometer with spring constraint |
DE4000903C1 (en) * | 1990-01-15 | 1990-08-09 | Robert Bosch Gmbh, 7000 Stuttgart, De | |
US5126812A (en) * | 1990-02-14 | 1992-06-30 | The Charles Stark Draper Laboratory, Inc. | Monolithic micromechanical accelerometer |
US5221400A (en) * | 1990-12-11 | 1993-06-22 | Delco Electronics Corporation | Method of making a microaccelerometer having low stress bonds and means for preventing excessive z-axis deflection |
US5233874A (en) * | 1991-08-19 | 1993-08-10 | General Motors Corporation | Active microaccelerometer |
US5313835A (en) * | 1991-12-19 | 1994-05-24 | Motorola, Inc. | Integrated monolithic gyroscopes/accelerometers with logic circuits |
US5534107A (en) * | 1994-06-14 | 1996-07-09 | Fsi International | UV-enhanced dry stripping of silicon nitride films |
-
1995
- 1995-01-27 US US08/379,751 patent/US5726480A/en not_active Expired - Lifetime
-
1996
- 1996-01-26 WO PCT/US1996/001343 patent/WO1996023229A1/en active Application Filing
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4945773A (en) * | 1989-03-06 | 1990-08-07 | Ford Motor Company | Force transducer etched from silicon |
US5357803A (en) * | 1992-04-08 | 1994-10-25 | Rochester Institute Of Technology | Micromachined microaccelerometer for measuring acceleration along three axes |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0870170A2 (en) * | 1995-12-24 | 1998-10-14 | Dan Haronian | Micro-electro-mechanics systems (mems) |
EP0870170A4 (en) * | 1995-12-24 | 2000-01-12 | Dan Haronian | Micro-electro-mechanics systems (mems) |
US5998816A (en) * | 1997-01-31 | 1999-12-07 | Mitsubishi Denki Kabushiki Kaisha | Sensor element with removal resistance region |
US6409876B1 (en) | 1997-05-13 | 2002-06-25 | Surface Technology Systems, Plc | Apparatus for etching a workpiece |
US6355181B1 (en) | 1998-03-20 | 2002-03-12 | Surface Technology Systems Plc | Method and apparatus for manufacturing a micromechanical device |
US7670203B2 (en) * | 2000-08-30 | 2010-03-02 | Agere Systems Inc. | Process for making an on-chip vacuum tube device |
Also Published As
Publication number | Publication date |
---|---|
US5726480A (en) | 1998-03-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5726480A (en) | Etchants for use in micromachining of CMOS Microaccelerometers and microelectromechanical devices and method of making the same | |
WO1996023229A9 (en) | Etchants for use in micromachining of cmos microaccelerometers and microelectromechanical devices and method of making the same | |
Rai-Choudhury | MEMS and MOEMS Technology and Applications | |
Polla | Microelectromechanical systems based on ferroelectric thin films | |
Bustillo et al. | Surface micromachining for microelectromechanical systems | |
Elwenspoek et al. | Mechanical microsensors | |
US6816301B1 (en) | Micro-electromechanical devices and methods of manufacture | |
Hoffman et al. | 3D structures with piezoresistive sensors in standard CMOS | |
Linder et al. | Surface micromachining | |
Zhang et al. | A lateral capacitive CMOS accelerometer with structural curl compensation | |
Enikov et al. | Three-dimensional microfabrication for a multi-degree-of-freedom capacitive force sensor using fibre-chip coupling | |
Lin | Selective encapsulations of MEMS: Micro channels, needles, resonators and electromechanical filters | |
Tay et al. | A differential capacitive low-g microaccelerometer with mg resolution | |
Song et al. | Micromachined inertial sensors | |
Tien | Silicon micromachined thermal sensors and actuators | |
CA2377189A1 (en) | Micro-electromechanical devices and methods of manufacture | |
Mokwa | Advanced sensors and microsystems on SOI | |
Gebhard et al. | Microtechnologies for microscaled robots and components | |
Schneider et al. | Integrated micromachined decoupled CMOS chip on chip | |
Sridhar et al. | Trench oxide isolated single crystal silicon micromachined accelerometer | |
Moore et al. | Silicon-on-insulator material for sensors and accelerometers | |
Smith et al. | Micromachined sensor and actuator research at the microelectronics development laboratory | |
Usenko et al. | SOI technology for MEMS applications | |
Lehto | SOI Microsensors and MEMS | |
Balan et al. | Platinum silicide as electrode material of microfabricated quantum electron tunneling transducers |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): CA JP KR SG |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE |
|
COP | Corrected version of pamphlet |
Free format text: PAGES 17-23,CLAIMS,REPLACED BY NEW PAGES 17-22;AFTER RECTIFICATION OF OBVIOUS ERRORS AS AUTHORIZED BY THE INTERNATIONAL SEARCHING AUTHORITY |
|
DFPE | Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101) | ||
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
122 | Ep: pct application non-entry in european phase |