WO2014001569A1

WO2014001569A1 - Molecule sensor that can be integrated into a mobile terminal

Info

Publication number: WO2014001569A1
Application number: PCT/EP2013/063835
Authority: WO
Inventors: Abdelkader Souifi; Vincent Aimez; Dominique Drouin; Jean-Pierre Cloarec
Original assignee: Institut National Des Sciences Appliquees De Lyon; Universite Claude Bernard Lyon 1; Centre National De La Recherche Scientifique (Cnrs); Ecole Centrale De Lyon; Universite De Sherbrooke
Priority date: 2012-06-29
Filing date: 2013-07-01
Publication date: 2014-01-03
Also published as: FR2992774B1; FR2992774A1

Abstract

The present invention concerns a device for detecting target molecules comprising a source (21) and a drain (22) extending on a substrate (10), and an island (23) between the source (21) and the drain (22), the island (23) forming a tunnel junction between the source (21) and the drain (22), characterised in that the device further comprises a nano-object (40) extending at right angles to the island (23), the nano-object (40) being functionalised to sense at least one target molecule.

Description

INTEGRABLE MOLECULE SENSOR IN A MOBILE TERMINAL

FIELD OF THE INVENTION

The present invention relates to the general technical field of semiconductor switching circuits, such as one-electron transistors (SETs) based for example on the Coulomb blocking mechanism.

The invention finds particular but not limited to application in the production of gas sensor type components, such as chemical or biological sensors integrable on the new generations of mobile phones.

BACKGROUND OF THE INVENTION

The evolution of information and communication technologies (ICT) has enabled the development of new generations of mobile phones operating on conventional radio frequency networks, 3G or WiFi, for example. These everyday objects make it possible, beyond telephone communications, to access various services via the Internet.

Thanks to the integration of GPS sensors, motion sensors, sound sensors and image sensors, these phones also allow new functionality for navigation, audio, video and many other applications.

These developments are notably related to the increase of memory capacity of these phones which allows the storage of software dedicated to these applications.

However, we note that some of these sensors consume a lot of energy at the expense of the autonomy of phones.

Moreover, at present, there is no telephone comprising a sensor for recording a taste or smell.

An object of the present invention is to provide a low-consumption sensor for capturing a taste or smell with a high sensitivity (of the order of some ppm), especially for use in a mobile terminal such as a mobile phone .

Another object of the present invention is to provide a method for obtaining such a sensor. More generally, an object of the present invention is to provide a low power semiconductor switching component and its associated manufacturing method. BRIEF DESCRIPTION OF THE INVENTION

For this purpose, the invention proposes a target molecule detection device comprising a source and a drain extending on a substrate, and an island between the source and the drain, the island forming a double tunnel junction between the source and the the drain, remarkable in that the device further comprises a nano-object extending to the right of the island, the nano-object being functionalized to capture at least one targeted molecule.

It will be understood in the following that when a layer A is mentioned as being "on" a layer B, it may be directly on the layer B, or may be located above the layer B and separated from said layer B by one or more intermediate layers.

It will also be understood that when a layer A is referred to as being "on" a layer B, it may cover the entire surface of the layer B, or a portion of said layer B.

The realization of a device as described above allows to obtain an autonomous sensor of taste or smell, compact and easily integrated into a phone.

Preferred but non-limiting aspects of the device according to the invention are the following:

the nano-object may be a nano-wire, preferably having a diameter of between 50 and 100 nanometers,

the nano-object can extend vertically or horizontally to the right of the island,

- The dimensions of the island can be as follows:

the length of the island can be between 30 and 70 nanometers, preferably equal to 50 nanometers,

the width of the island can be between 10 and 30 nanometers, preferably equal to 20 nanometers, the thickness of the island may be between 1 and 10 nanometers, preferably equal to 5 nanometers;

- The distance between the island and the source and the island and the drain may be between 1 and 10 nanometers.

The invention also relates to a method for manufacturing a target molecule detection device, characterized in that it comprises the following steps:

forming on a substrate such as silicon, a source, a drain and an island between the source and the drain, to form a single-electron transistor,

the formation of a nano-object such as a nanowire at the right of the island,

the functionalization of the nano-object to allow the capture of at least one targeted molecule.

the step of forming the source, the drain and the island may comprise the deposition of an electrically insulating layer on the substrate and the formation of the source, the drain and the island in the electrically insulating layer;

the method may further comprise, prior to the step of forming the nano-object, a step of depositing an insulating layer on the source, the drain and the island;

the step of forming the nano-object may comprise:

o the introduction of the mono-electron transistor into a growth chamber,

depositing a liquid catalyst pad at the right of the island, and

o the growth of the nano-object between the catalyst pad and the island by introducing a gaseous mixture based on silicon in the growth chamber;

the process may further comprise, prior to depositing the liquid catalyst pad, the following steps:

o the deposition of a mask on the source, the drain and the island,

o the insolation of the mask above the island by electronic lithography to create a growth pattern of the nano-object. The invention also relates to a mobile terminal comprising communication means and processing means, remarkable in that it comprises at least one device as described above. BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more apparent from the following description of several alternative embodiments, given by way of non-limiting examples, from the attached drawings in which:

FIG. 1 diagrammatically illustrates an embodiment of the component according to the invention,

FIG. 2 schematically illustrates a network of components according to the invention,

FIG. 3 is a partial schematic representation of the component according to the invention;

FIG. 4 illustrates an exemplary method of manufacturing the component according to the invention,

FIG. 5 illustrates a source / drain electric current curve as a function of a source / island electrical voltage,

FIG. 6 illustrates another example of a method of manufacturing the component according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the component according to the invention and its associated manufacturing method will now be described with reference to the figures. In these different figures, the equivalent elements of the circuit and of the method bear the same numerical references.

Although the idea of associating an "electronic nose" with mobile phones is already quite widespread, the technical solutions allowing the integration of such a feature face the problems of energy consumption.

Most current gas sensors use resistance variation measurements or optical measurements. A disadvantage of these sensors is that they are active at high temperatures, which requires providing a significant amount of energy. The present invention proposes to provide a low-consumption chemical or biological sensor based on nanotechnologies. Advantageously, this type of sensor can operate at ambient temperature, and can be integrated directly on silicon CMOS electronic chips that enable data processing.

The invention is based on the use of a new type of sensor allowing an individual count of the targeted molecules. These sensors use a technology combining:

nanoscale bio-antennas, such as nano-wires, for the reception function of the targeted molecules, and

- Mono-electron transistors (or "SET", acronym for the expression "single electron transistor") for transduction.

Referring to Figure 1, there is illustrated an alternative embodiment of the electronic component according to the invention.

The component comprises a substrate 10 such as a silicon substrate. The component also comprises a first layer 20 electrically insulating on the substrate. This first insulating layer is for example a layer of silicon oxide SiO 2 or titanium oxide ΤΊΟ 2.

On the first electrically insulating layer, the component comprises a source 21, a drain 22, and an island 23 between the source 21 and the drain 22. A first tunnel junction is formed between the source 21 and the batch 23 and a second tunnel junction is formed between the i lot 23 and the drain 22.

Preferably, the tunnel junction surfaces between the source 21 and the island 23 on the one hand and between the island 23 and the drain 22 on the other hand are the smallest possible. This makes it possible to minimize the capacity of the tunnel junctions and thus to increase the operating temperature of the component.

More precisely, the width "I" and the thickness "e":

the face 21 1 of the source 21 opposite the block 23,

the face 231 of the island 23 opposite the source 21,

the face 232 of the island 23 facing the drain 22, and

the face 221 of the drain 22 opposite the block 23, are chosen so as to minimize the area of these faces (see Figure 3).

To do this, the thickness "e" of each of these faces may be chosen less than 10 nanometers, preferably less than 5 nanometers, and even more preferably less than or equal to 3 nanometers. Similarly, the width "I" of these faces may be chosen less than 100 nanometers, preferably less than 50 nanometers, and even more preferably less than or equal to 30 nanometers.

For an electron transistor (SET) made of titanium, the following dimensions make it possible to obtain a sensor operating at ambient temperature and having a total capacity of 0.52 aF:

Thickness of Ti: 2 nm

o Width of Ti lines: 20 nm

o Source / island and island / source distance: 8 nm with TiOx

o Island length: 50 nm

Island / nano-object distance: 20 nm with Si02

o Nano-object / island surface: 50 nm x 20 nm

These dimensions make it possible to obtain a source source / island and drain / island of 0.17 aF as well as an island / nano-object capacity of 0.17 aF.

With a total capacity of 0.52 aF, the charge energy is 309 meV, which is more than enough for room temperature operation.

Indeed, the charge energy (q / CTotal) of the island is preferably higher than the thermal energy kT (in practice, it is possible for example to choose Ec> 10 kT, ie Ec> 260 meV) to allow a operation of the sensor at room temperature T. Those skilled in the art will appreciate that the total capacity of the "CTotal" island corresponds to the sum of the island / source, island / drain and island / gate capacitors (the functionalised nano-object serving as the grid in the case of the sensor shown in Figure 1.

In the embodiment illustrated in Figure 1, the distance "d" between the source 21 and the lot 23 i is equal to the distance "d '' between I ^* i Lot 23 and the drain 22. This distance" d Is between 2 and 10 nm, in particular depending on the dielectric chosen. For example, the distance "d" may be between 2 and 3 nm when the material constituting the dielectric is SiO 2. The distance "d" can be between 6 and 10 nm when the material constituting the dielectric is TiOx. The island 23 is for example titanium. The dimensions of batch 23 can be variable. By way of non-limiting example, the length "L" and the width "I" of the island 23 may be between 10 and 100 nanometers. However, the length "L" and the width "I" of the island 23 are preferably greater than 10 nanometers to facilitate the positioning of a nano-wire 40 to the right of the island 23. In the illustrated embodiment in Figure 1, the island 23 has a length of 50 nanometers, a width of 20 nanometers and a thickness of 5 nanometers.

The component also comprises a second layer 30 electrically insulating on the island 23. This layer allows a capacitive coupling between the island 23 and the nano-object 40.

Finally, the component comprises a nano-object 40 on the second insulating layer 30. This nano-object 40 forms an antenna for the detection of molecules. The nano-object is for example a metal nano-wire or a nano-silicon wire with a diameter of between 50 and 100 nanometers.

In the context of the present invention, the term "nano-object" is intended to mean a body of which at least one of the dimensions (length, diameter, thickness) is of the order of one nanometer, that is to say less than 500 nanometers and preferably less than 100 nanometers.

Advantageously, the nano-wire 40 extends horizontally or vertically to the right of the island 23. In other words, the nano-wire 40 extends over the second insulating layer 30 above the island 23, the longitudinal axis AA 'of the nano-wire 40 passing through the island 23.

The fact that the nano-wire 40 extends vertically to the right of the island 23 has many advantages. In particular, this vertical configuration makes it easier to detect certain molecules with respect to a horizontal configuration.

Nano-wire 40 is functionalized using a functionalization method known to those skilled in the art. This functionalization makes it possible to increase the chemical and / or biological compatibility of the nano-thread 40 with a targeted molecule. This functionalization induces the creation of keys 41 capable of capturing the target molecule 42. The creation of keys 41 on the nano-wire 40 makes it possible to obtain an antenna capable of specifically recognizing a particular type of molecule. The operating principle of the component illustrated in Figure 1 is as follows. A molecule 42 is captured by a key 41 of the nano-wire 40. This capture of a molecule 42 by the nano-wire 40 gives rise to an exchange of electric charges (arrivals or departure of electrons) between the molecule 42 and the nano-wire 40 forming an antenna. The variation of the potential of the nano-object resulting from the charge exchange induces a charge variation of the island of the transistor with an electron. The one-electron transistor - composed in particular of the source 21, the drain 22 and the batch 23 - then allows the counting of the molecules of interest by counting individual electric charges.

In practice, the measurements of the electrical voltage V _D s between the source and the drain on the one hand and the electrical current ID _S between the source and the drain on the other hand make it possible to determine the number of electrons exchanged and therefore the number of molecules captured. Indeed, V _D s and l _D s vary according to the number of loads in the island, as shown in Figure 5.

For example if we assume that:

- when adding an electron, the curve of the current l _D s as a function of the voltage

Screw is shifted by an AV difference of 50 millivolts, and that

each key exchanges an electron with a captured molecule,

Then an offset of 150 millivolts implies that 3 molecules were captured.

This sensitivity depends on the coupling capacity between the island and the nano-object. With reference to FIG. 2, there is illustrated a matrix 50 comprising a plurality of components 60 such as the component illustrated in FIG. 1. Each component 60 can be functionalized to recognize:

- the same type of molecule,

- a different type of molecules.

The use of a network of components 60 forming sensors with different functionalizations makes it possible to have a chip of chemical sensors (or a bio-chip) allowing the determination of several chemical and / or biological species sequentially or simultaneously.

In a variant, the networking of a plurality of functionalized sensors to the detection of the same molecule makes it possible to increase the sensitivity to the same species of the matrix thus obtained. The component according to the invention has many advantages, especially with respect to a biosensor composed of a MOS transistor and a nano-wire extending horizontally between the source and the drain of said MOS transistor.

In particular, the use of a single-electron transistor makes it possible to obtain an electronic sensor of greater sensitivity. The use of a mono-electron transistor also limits the power consumption of the component according to the invention. Finally, the presence of a nano-wire extending vertically I ^* i lot right facilitates component fabrication according to the invention, in particular by avoiding the difficulties associated with connecting a nanowire between a source and a drain (which requires the realization of good ohmic contacts between the nano-wire, the source and the drain).

An example of a method of manufacturing the circuit illustrated in FIG. 1 will now be described.

In one step of the method, a single-electron transistor (or "SET") is created by any technique known to those skilled in the art such as the method described in the document. WO01 / 1689.

A first electrically insulating layer 20 is formed on a silicon substrate 10 (step 100). This first insulating layer 20 may be formed by oxidation of the silicon substrate 10 to obtain a first insulating layer 20 of silicon oxide (SiO2).

A source 21, a drain 22, and a block 23 are formed (step 200) in the first insulating layer 20, the batch 23 being disposed between the source 21 and the drain 22.

Once the mono-electron transistor has been manufactured, a second electrically insulating layer 30 is deposited on the island 23 (step 300). Preferably, the second insulating layer 30 has a thickness of between 5 and 10 nm.

Next, a nano-wire 40 is formed in line with the island 23 of the mono-electron transistor.

A mask is deposited on the second insulating layer 30. This mask is insulated above the island 23 using an electronic lithography technique (also known as "electron beam lithography") to create a pattern nano-wire growth. The use of an electronic lithography technique makes it easier to align the nano-wire on the island. Then VLS (acronym for the expression "Vapor-Liquid-Solid") is formed to form nano-wire 40. It is made by means of a liquid catalyst through which the atoms of the vapor phase are absorbed and diffuse towards the second insulating layer. Nucleation occurs at the interface between the liquid catalyst and the second insulating layer.

A liquid catalyst pad 70 is deposited on the second insulating layer 30 to the right of the island 23 (step 400). More specifically, the liquid catalyst pad 70 is deposited on the pattern obtained by electronic lithography. The liquid catalyst 70 may be gold, platinum, cobalt or any other liquid catalyst known to those skilled in the art. The use of gold or cobalt as a liquid catalyst has the advantage of limiting the manufacturing temperature of the nanowire (approximately 500 ° C.) and thus of limiting the risks of degradation of the mono-electron transistor.

Once the liquid catalyst block 70 has been deposited, a gaseous mixture - for example of SiH4 - is applied. The liquid catalyst pad 70 becomes saturated and a crystallization of silicon is observed under the liquid catalyst pad 70, that is to say between the liquid catalyst and the second electrically insulating layer (step 500).

This induces the creation of a nano-wire 40 of silicon, of nanometric diameter (i.e between 1 and 900 nm) and of length without stress defined according to the intended application.

Once the nano-wire 40 has been created, the liquid catalyst pad 70 can be removed from the top of the nano-wire 40.

Nano-wire 40 is then functionalized to allow the capture of targeted molecules (step 600). This functionalization can be implemented using any functionalization technique known to those skilled in the art.

With reference to FIG. 6, another example of a method for obtaining the circuit illustrated in FIG. 1 is illustrated.

The method comprises a first step of producing a silicon oxide layer on a silicon substrate. A slice 810 is then produced in the silicon oxide layer, the slice having for example a width of 20 nm, a length of 250 nm, and a depth of 20 nm (step 81). In another step, a deposit (step 82) of a titanium layer 820 is made on a portion of the surface of the substrate. This titanium layer extends transversely to the wafer (for example perpendicular to the wafer), at the center thereof. This titanium layer has for example a width of 50 nm, a depth of 50 nm and a length of 60 nm. The deposition of the titanium layer is for example carried out by an electron beam lithography technique.

An oxidation (step 83) of the titanium layer is then carried out to obtain an overlayer of titanium oxide TiOx 830 with a thickness of 8 nm.

In another step of the method, a layer of titanium 840 - for example of thickness 20 nm - is deposited (step 84) over the entire surface of the substrate.

Polishing is then carried out - such as chemical mechanical polishing (or "CMP") - of the entire surface of the substrate so as to obtain a layer titanium 2 to 3 nm thick covering the wafer in the silicon oxide layer (step 85).

In another step of the method, a silicon oxide layer is deposited (step 86) over the entire surface of the substrate so as to cover the wafer containing the titanium layer.

Finally, a nano-wire 870, 880 vertical (step 88) or horizontal (step 87) is produced on the silicon oxide layer.

The use of single-electron transistor in the component according to the invention makes it possible to lift a very important lock in the field of odor sensors or electronic taste, namely the energy consumption. In fact, the monoelectron transistors are fast enough for the charge sensor functions and for the interfacing circuits between the chemical and / or biological sensors and the CMOS data processing and transmission circuits.

The integration of the component illustrated in FIG. 1 on an electronic chip makes it possible to replace the external sensors used in the existing gas detectors by internal sensors, which can be arranged on telescopic supports if necessary. In particular, the component according to the invention can be used as a gas sensor for the safety of people:

- control of the quality of the air inside a structure (home, vehicle, etc.),

- outdoor air quality control

- detection of toxic or explosive gases.

- measurement of a hygrometry rate, etc.

The component according to the invention can also be used as a biological sensor, for example as an ethyltest, or for controlling the composition of a liquid such as water.

Advantageously, the previously described component can be integrated on a mobile terminal chip - such as a mobile phone - which comprises means for appropriate processing of the information captured by the component illustrated in FIG.

In this case, an "air quality control inside a structure" function can for example be activated on a telephone to detect an abnormal increase in a quantity of carbon monoxide. The phone can simply activate a ringtone to inform people on the spot of this anomaly, or to prevent help by sending a call or a text message. Similarly, for an "outside air quality control" function, the information picked up by the component according to the invention can be transmitted over a network. The management of the data sent by a set of users can then make it possible to map the air quality in a given territory.

Also in the case of an integration of the component described above in a mobile phone, it is possible to consider de-energizing the phone when detecting an explosive gas to avoid any risk of explosion related to the electric current supplying the phone.

The reader will have understood that many modifications can be made to the component and manufacturing process described above without physically going out of the new teachings presented here. It is therefore obvious that the examples which have just been given are only illustrations that are in no way limitative.

Claims

A target molecule detection device comprising a source (21) and a drain (22) extending on a substrate (10), and an island (23) between the source (21) and the drain (22), block (23) forming a double tunnel junction between the source (21) and the drain

(22), characterized in that the device further comprises a nano-object (40) extending to the right of the island (23), the nano-object (40) being functionalized to capture at least one targeted molecule. 2 Device according to claim 1, wherein the nano-object (40) is a nano-wire, preferably of diameter between 50 and 100 nanometers.

3 Device according to claim 1 or claim 2, wherein the nano-object (40) extends vertically or horizontally to the right of the island (23).

Device according to any one of claims 1 to 3, wherein:

the length (L) of the island (23) is between 30 and 70 nanometers, preferably equal to 50 nanometers,

the width (I) of the island (23) is between 10 and 30 nanometers, preferably equal to 20 nanometers

- The thickness (e) of the island is between 1 and 10 nanometers, preferably equal to 5 nanometers.

5 Apparatus according to any one of claims 1 to 4, wherein the distance (d) between the island and the source and the island and the drain is between 1 and 10 nanometers.

Process for manufacturing a target molecule detection device, characterized in that it comprises the following steps: the formation (200) on a substrate (10) such as silicon, a source, a drain and an island between the source and the drain, to form a monoelectron transistor,

the formation (500) of a nano-object such as a nano-thread at the right of the batch,

functionalization (600) of the nano-object to allow the capture of at least one targeted molecule. The manufacturing method according to claim 6, wherein the step of forming the source, the drain and the island comprises depositing (100) an electrically insulating layer on the substrate and forming the source, drain and the island in the electrically insulating layer. Manufacturing method according to any one of claims 6 or 7, which further comprises, prior to the step of forming the nano-object, a step of depositing (300) an insulating layer on the source, the drain and the small island. The method of any of claims 6 to 8, wherein the step of forming the nano-object comprises:

the introduction of the mono-electron transistor into a growth chamber,

depositing a liquid catalyst pad at the right of the island, and

the growth of the nano-object between the catalyst pad and the island by introducing a gaseous mixture based on silicon into the growth chamber. The method of claim 9, which further comprises, prior to the deposition of the liquid catalyst pad, the following steps:

- the deposit of a mask on the source, the drain and the island,

- the insolation of the mask above the island by electronic lithography to create a growth pattern of the nano-object. Mobile terminal comprising communication means and processing means, characterized in that it comprises at least one device according to one of claims 1 to 5.