WO1999016929A1

WO1999016929A1 - Liquid reagent delivery system

Info

Publication number: WO1999016929A1
Application number: PCT/US1998/020020
Authority: WO
Inventors: Edward A. Sturm; Peter S. Kirlin; Peter C. Van Buskirk; Dennis F. Brestovansky
Original assignee: Advanced Technology Materials, Inc.
Priority date: 1997-09-26
Filing date: 1998-09-25
Publication date: 1999-04-08
Also published as: AU9507298A

Abstract

A liquid delivery system (110) dispensing a liquid (114) for subsequent processing. The liquid delivery system in one embodiment comprises a pressurizable reservoir (112) for holding a liquid (114), a pressurizing gas source (118) coupled with the reservoir (112) and constructed and arranged to selectively impose a pressure on liquid (114) therein to effect discharge of liquid (114) from the reservoir (112), and a liquid mass flow controller (150) joined in liquid flow relationship to the reservoir (112) for receiving the liquid (114) discharged therefrom, and for dispensing the liquid (114) after flowing through the mass flow controller (150), as a flow-controlled liquid stream. The flow-controlled liquid stream may for example be a precursor liquid reagent for a vapor deposition process, which is vaporized subsequent to dispensing to form a reagent source vapor for chemical vapor deposition (CVD) or other vapor deposition process.

Description

LIQUID REAGENT DELIVERY SYSTEM

Field of the Invention

This invention relates generally to an apparatus and method for delivery of liquid reagents, by which liquid may be dispensed to downstream equipment and operations, e.g., downstream vaporization of a dispensed liquid reagent, for transport of the resulting vapor to a deposition zone such as a chemical vapor deposition (CVD) reactor.

Description of the Related Art

In the formation of thin films, layers and coatings on substrates, a wide variety of source materials have been employed. These source materials include reagents and precursor materials of widely varying types, and in various physical states. To achieve highly uniform thickness layers of a conformal character on the substrate, vapor phase deposition has been used widely as a technique. In vapor phase deposition, the source material may be of initially solid form that is sublimed or melted and vaporized to provide a desirable vapor phase source reagent. Alternatively, the reagent may be of normally liquid state, which is vaporized, or the reagent may be in the vapor phase in the first instance.

In the manufacture of advanced thin film materials, a variety of reagents may be used. These reagents may be used in mixture with one another in a multicomponent fluid that is utilized to deposit a corresponding multicomponent or heterogeneous film material. Such advanced thin film materials are increasingly important in the manufacture of microelectronic devices and in the emerging field of nanotechnology. For such applications and their implementation in high volume commercial manufacturing processes, it is essential that the film morphology, composition, and stoichiometry be closely controllable. This in turn requires highly reliable and efficient means and methods for delivery of source reagents to the locus of film formation.

Examples of advanced thin film materials include refractory materials such as high temperature superconducting (HTSC) materials including YBa₂Cu3θ_x, wherein x is from about 6 to 7.3, BiSrCaCuO, and TIBaCaCuO. Barium titanate, BaTiθ3, and barium strontium titanate, Ba_xSrι._xTiθ3, have been identified as ferroelectric and photonic materials with unique and potentially very useful properties in thin film applications of such materials. Ba_xSrι__xNb₂θ₆ is a photonic material whose index of refraction changes as a function of electric field and also as a function of the intensity of light upon it. Lead zirconate titanate, PbZri__xTi_xO3, is a ferroelectric material whose properties are very interesting. The Group II metal fluorides, BaF2, CaF2, and SrF2, are useful for scintillation detecting and coating of optical fibers. Refractory oxides such as Ta2U5 are coming into expanded use in the microelectronics industry; Ta₂U₅ is envisioned as a thin-film capacitor material whose use may enable higher density memory devices to be fabricated.

Thin films comprising the Group π metal fluorides, BaF₂, CaF₂, and SrF₂, are potentially very useful as buffer layers for interfacing between silicon substrates and HTSC or GaAs overlayers or between GaAs substrates and HTSC or silicon overlayers, and combinations of two or all of such metal fluorides may be employed in forming graded compositions in interlayers providing close lattice matching at the interfaces with the substrate and overlayer constituents of the composite. For example, a silicon substrate could be coated with an epitaxial layer of BaF₂/CaF₂, SrF₂/CaF₂, or SrF₂/CaF₂/BaF₂, whose composition is tailored for a close lattice match to the silicon. If the ratio of the respective Group II metal species in the metal fluoride interlayers can be controlled precisely in the growth of the interlayer, the lattice constant could be graded to approach the lattice constant of GaAs. Thus, a gallium arsenide epitaxial layer could be grown over the metal fluoride interlayer, allowing the production of integrated GaAs devices on widely available, high quality silicon substrates. Another potential use of such type of metal fluoride interlayers would be as buffers between silicon substrates and polycrystalline HTSC films for applications such as non-equilibrium infrared detectors. Such an interlayer would permit the HTSC to be used in monolithic integrated circuits on silicon substrates.

BaTiO₃ and Ba_xSrι-_xNb₂O₆ in film or epitaxial layer form are useful in photonic applications such as optical switching, holographic memory storage, and sensors. In these applications, the BaTiO₃ or Ba_xSrι__xNb₂O₆ film is the active element. The related ferroelectric material PbZrι._xTi_xO₃ is potentially useful in infrared detectors and thin film capacitors well as filters and phase shifters.

Chemical vapor deposition (CVD) is a particularly attractive method for forming thin film materials of the aforementioned types, because it is readily scaled up to production runs and because the electronic industry has a wide experience and an established equipment base in the use of CVD technology which can be applied to new CVD processes. In general, the control of key variables such as stoichiometry and film thickness, and the coating of a wide variety of substrate geometries is possible with CVD. Forming the thin films by CVD permits the integration of these materials into existing device production technologies. CVD also permits the formation of layers of the refractory materials that are epitaxially related to substrates having close crystal structures.

CVD requires that the element source reagents, i.e., the precursor compounds and complexes containing the elements or components of interest must be sufficiently volatile to permit gas phase transport into the chemical vapor deposition reactor. The elemental component source reagent must decompose in the CVD reactor to deposit only the desired element at the desired growth temperatures. Premature gas phase reactions leading to particulate formation must not occur, nor should the source reagent decompose in the lines before reaching the reactor deposition chamber. When compounds are desired to be deposited, obtaining optimal properties requires close control of stoichiometry that can be achieved if the reagent can be delivered into the reactor in a controllable fashion. In this respect the reagents must not be so chemically stable that they are non-reactive in the deposition chamber.

Desirable CVD reagents therefore are fairly reactive and volatile. Unfortunately, for many of the refractive materials described above, volatile reagents do not exist. Many potentially highly useful refractory materials have in common that one or more of their components are elements, i.e., the Group II metals barium, calcium, or strontium, or the early transition metals zirconium or hafnium, for which no or few volatile compounds well-suited for CVD are known. In many cases, the source reagents are solids whose sublimation temperature may be very close to the decomposition temperature, in which case the reagent may begin to decompose in the lines before reaching the reactor, and it therefore is very difficult to control the stoichiometry of the deposited films from such decomposition - susceptible reagents.

When the film being deposited by CVD is a multicomponent substance rather than a pure element, such as barium titanate or the oxide superconductors, controlling the stoichiometry of the film is critical to obtaining the desired film properties. In the deposition of such materials, which may form films with a wide range of stoichiometries, the controlled delivery of known proportions of the source reagents into the CVD reactor chamber is essential. In other cases, the CVD reagents are liquids, but their delivery into the CVD reactor in the vapor phase has proven difficult because of problems of premature decomposition or stoichiometry control. Examples include the deposition of tantalum oxide from the liquid source tantalum ethoxide and the deposition of titanium nitride from bis(dialkylamide)titanium reagents.

While source reagent liquid delivery systems present distinct advantages over conventional techniques, there is often some fraction of the precursor compound that decomposes into very low volatility compounds that remain at the vaporization zone. This deficiency is an important issue in the operation of CVD processes that use thermally unstable solid source precursors that undergo significant decomposition at conditions needed for sublimation. Such decomposition can occur in all reagent delivery systems that involve a vaporization step, including flash vaporizer liquid delivery systems as well as more conventional reagent delivery systems that include bubblers and heated vessels operated without carrier gas.

Although well-behaved CVD precursors vaporized under "ideal" conditions will form no deposits or residue at the vaporization zone, deviations from this situation are common and can be divided into several categories:

1) Reactive impurities in either the precursor or in the carrier gas decompose at the vaporizer temperatures.

2) Spatial and temporal temperature variations occur in the vaporization zone, with temperatures in some regions being sufficient to bring about decomposition.

3) CVD precursors are employed which are thermally unstable at the sublimation temperature.

Optimization of the conditions used in the vaporizer of reagent delivery systems can minimize the fraction of the delivered precursor that decomposes (and remains) at the vaporization zone, but virtually all solid and liquid precursors undergo some decomposition when they are heated for conversion to the gas phase, although this fraction is negligibly small in "well-behaved" compounds. Use of precursors that tend to decompose near their vaporization temperature may be mandated by availability (i.e., where the selected precursor possesses the best properties of available choices) or by economics, where precursor cost is strongly dependent on the complexity of its synthesis.

Additionally, CVD precursors often contain impurities, and the presence of those impurities can cause undesirable thermally activated chemical reactions at the vaporization zone, also resulting in formation of involatile solids and liquids at that location. For example, a variety of CVD precursors (such as tantalum pentaethoxide) are water-sensitive and hydrolysis can occur at the heated vaporizer zone forming tantalum oxide particulates that may be incorporated into the growing tantalum oxide film with deleterious effects.

Despite the advantages of the liquid delivery approach (which include improved precision and accuracy for most liquid and solid CVD precursors and higher delivery rates), the foregoing deficiencies pose a serious impediment to widespread use of the vaporization liquid delivery technique for providing volatilized reagent to the CVD reactor.

Improved liquid delivery systems are disclosed in U.S. Patent 5,204,314 issued April 20, 1993 to Peter S. Kirlin et al. and U.S. Patent 5,536,323 issued July 16, 1996 to Peter S. Kirlin et al., which describe heated foraminous vaporization structures such as microporous disk elements. In use, liquid source reagent compositions are flowed onto the foraminous vaporization structure for flash vaporization. Vapor thereby is produced for transport to the deposition zone, e.g., a CVD reactor. The liquid delivery systems of these patents provide high efficiency generation of vapor from which films may be grown on substrates. Such liquid delivery systems are usefully employed for generation of multicomponent vapors from corresponding liquid reagent solutions containing one or more precursors as solutes, or alternatively from liquid reagent suspensions containing one or more precursors as suspended species.

The art continues to seek improvements in liquid delivery systems for vapor- phase formation of advanced materials, as well as improvements in ancillary equipment such as fluid transport, vaporizer, mixing, and control means associated with the liquid delivery system, and process conditions and techniques for operating the liquid delivery system and ancillary equipment in a maximally efficient manner. One area in which improvement is sought relates to the motive means used to deliver liquid reagents from a storage reservoir to the vaporizer of the deposition system.

Although positive displacement pumps have been employed in prior art liquid delivery and vaporization systems, they have attendant disadvantages that limit their utility. These deficiencies include inadequate durability and reliability, and the susceptibility of the reagents transported under the impetus of such systems to deleteriously interact with the environment. The positive displacement pump is expensive to repair or replace, and consumes a disproportionate portion of the time spent on technical service in the maintenance of the system. Its unsuitability in the reagent transport application relates to the fact that the positive displacement pump was never designed to run continuously for long periods of time, particularly in the movement of air-sensitive chemistries.

In a typical embodiment of a positive displacement pump in a liquid delivery and vaporization system, the pumping action of the pump is dependent on the movement of pistons between the surrounding environment and the reagent liquid, through high density polyethylene seals. These seals are made to fit in a physically tight manner to the piston surface, but such arrangement inherently cannot provide an ultra-high integrity seal. Inevitably, some amount of the reagent adheres to the piston surface and is transported through the seals to the outside environment. Likewise, some of the outside environment is carried back through the seals to the chemical reagent environment. Although this occurrence may be compensated for to some extent by a rigid inert fluid purging protocol, the fact remains that the positive displacement pump does not represent an ideal design for long term use with air and moisture reactive reagents.

Among the advantageous aspects of the positive displacement pump are its ability to aid mixing, such as where reagent mixtures are employed in the formation of multi -component films via CVD, and the rapid start-up response of the positive displacement pump. In operation of the positive displacement pump, there is virtually no ramp to a desired flow rate and no overshoot of the set point for the pump. Very little inert push (displacement) gas pressure is required since the pump provides the pressure needed to move the liquid. Turbulent flow is generated by the pump, which aids in the mixing of the aforementioned multicomponent reagent solutions. Additionally, the agreement between the flow set point and the actual flow is very linear for reliable calibration and good repeatability.

Characteristics of the positive displacement pump which limit its usefulness, apart from the questionable seal integrity discussed above, include: the lack of output for feedback to the user verifying flow and flow rate; moving parts in contact with the reagent which could lead to contamination and particle generation (always an issue for microdevice fabrication, electronic thin film production, and semiconductor processing); the limited range of achievable flow rates (making transitions from research to commercial implementation less than straightforward); pulsing of flow and pressure due to piston movement (necessitating the use of a pulse damper and even then resulting in some non-uniformity at very low flow rates); and perhaps less than optimal accuracy of flow control (e.g., at levels on the order of + 3% versus + 1 to 2% claimed by other flow control devices).

The positive displacement pump system is also considered somewhat complicated by users (even in the research environment where it is most commonly used), has a mean time to repair (MTR) which is too short for practical use in the semiconductor industry, and is difficult to repair or adjust. Such characteristics thus pose a significant barrier to the widespread commercial use of liquid delivery and vaporization systems for applications such as CVD. There is therefore a substantial and continuing need in the art for an alternative liquid metering device overcoming the various deficiencies of the positive displacement liquid pumps heretofore used.

As mentioned, positive displacement pumps have the advantage of facilitating mixing in instances where multi-reagent mixtures are utilized for formation of corresponding CVD-applied films. Thus, the use of alternative liquid metering and flow devices results in the loss of such advantages, and creates potential problems with respect to mixing and delivery of multi-reagent precursor compositions. Multi- component precursor compositions are utilized for formation of a wide variety of films, e.g., mixed oxide films, ferroelectrics, superconductor materials, barium strontium titanate films, strontium bismuth tantalate films, lead lanthanum zirconium titanate films, etc.

For a number of such multi-component films, single source reagents are not available or even feasible in many cases, and "cocktail" precursor compositions (containing multiple precursor compounds, in solution or utilized as a combination of solutions) either have not been developed or, if developed, may not be stable over extended periods of time. Additionally, real-time mixing of reagent components may be desired for other processing reasons, such as enabling the capability of changing precursor component ratios relative to one another, in order to provide graded deposited films, or for sequential deposition of multi-layer films each of which has a distinct composition. For these reasons, it is highly desirable to provide a liquid delivery system with the capability for mixing multiple reagents in situ, at the processing locus.

In instances where short-term capability and stability of the precursor composition is not an issue, and vaporization of multiple source reagents can be accomplished in the same temperature regime, on-line premixing of a large volume of precursors with one another is a potential solution to the co-delivery problems associated with multiple reagents. Standard mixing manifolds may not be able to accommodate enough material to allow the user to mix the precursor multi-component composition and then pressurize same for delivery by means other than positive displacement pumps, e.g., with two-stage pumping. Since commercial scale CVD operations require large volumes of source reagent compositions, such precursor compositions may need to be delivered at elevated pressures, e.g., above 25 psi. As a further problem, the flow turbulence created by high pressure piston movement in positive displacement pumps is lost if such positive displacement pumps are not employed, so that homogeneity of the mixed precursor composition may be reduced by the use of alternative liquid motive transport means, if separate and additional means are not employed to remedy such deficiency when positive displacement pumps are not present in the process system. It would therefore be a significant advance in the art to provide a liquid delivery system accommodating a wide variety of source reagent precursors, which does not utilize positive displacement pumps, but nonetheless is highly efficient in construction and operation.

Accordingly, it is an object of the present invention to provide an improved liquid delivery and vaporization system for introduction of CVD source reagent precursors to CVD reactors.

It is another object of the invention to provide an improved liquid metering means and method for delivery of liquid reagents from a supply vessel containing same to the vaporization locus at which the liquid reagent is volatilized for transport to a deposition locus, e.g., a CVD reactor. It is a further object of the invention to provide a mixing means that is usefully employed in a liquid delivery system for delivery of multi-component source reagent compositions to a vaporizing locus for subsequent deposition of material on a suitable substrate.

It is another object of the invention to provide an improved liquid mixing and delivery means permitting delivery of multi -component source reagent compositions to vaporizer and deposition apparatus, at elevated pressures, e.g., up to and above 25 psi.

Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.

SUMMARY OF THE INVENTION

The present invention relates to a liquid delivery apparatus and method, for dispensing a liquid to downstream equipment or operations. Such liquid may for example comprise a reagent that is dispensed to a downstream vaporization system, in which the liquid reagent is vaporized for subsequent vapor-phase deposition of material therefrom on a substrate.

In one aspect, the invention relates to a liquid delivery system, comprising:

a pressurizable reservoir for holding a liquid;

a pressurizing gas source coupled with the reservoir and constructed and arranged to selectively impose a pressure on liquid therein to effect discharge of liquid from the reservoir; and

a liquid mass flow controller joined in liquid flow relationship to the reservoir for receiving the liquid discharged therefrom, and for dispensing the liquid after flow through the mass flow controller, as a flow-controlled liquid stream.

Such liquid delivery system may further comprise mixing means, e.g., a mixing vessel, mixing valve or mixing manifold, joined in liquid flow relationship to the liquid mass flow controller for receiving the flow-controlled liquid stream therefrom, with a source of at least one other liquid joined in liquid flow relationship to the mixing means, for mixing the liquids introduced thereto and discharging a mixed liquid stream. The source of such at least one other liquid may be similarly constructed and comprise a second pressurizable reservoir for holding a second liquid, and a second pressurizing gas source coupled with the second reservoir to impose a pressure on the liquid therein to effect discharge of liquid from the second reservoir to the mixing means.

In another aspect, the invention relates to a liquid delivery and vaporization system, comprising a liquid delivery system as variously described hereinabove, and a vaporizer receiving the flow-controlled liquid stream for vaporization thereof to form a vapor. A still further aspect of the invention relates to a liquid delivery, vaporization and deposition system, comprising a liquid delivery and vaporization system of the type variously described above, and means for receiving said vapor and depositing material on a substrate therefrom, such as a vapor deposition chamber containing the substrate therein.

Another aspect of the invention relates to a liquid reagent delivery system for delivering a multicomponent reagent material from independent liquid reagent sources from which the individual reagents may vary in pressure relative to one another. Such liquid reagent delivery system comprises a supply manifold coupled in supply relationship to the respective liquid reagent sources, wherein the supply manifold is physically divided into discrete segments by pressure-deformable separation elements. Each segment of the supply manifold is arranged to discharge to a mixing means. The pressure-deformable separation elements are responsively deformable to pressure so that volume of respective segments of the supply manifold are dynamically allocated in response to pressure, to equalize the pressure in the supply manifold, and thereby accommodate pressure variation of the respective liquid reagents flowed to the supply manifold.

Another aspect of the invention relates to a liquid reagent delivery system including a mixing vessel receiving respective liquid reagents from sources thereof coupled in flow relationship to the mixing vessel, for discharge of a mixed multicomponent liquid from the mixing vessel, wherein pressure of the respective liquid reagents is independently variable at the respective sources thereof. Such system comprises means for sensing pressure of each liquid reagent and responsively adjusting flow of the respective liquid reagents to maintain a predetermined composition of the mixed multicomponent liquid discharged from the mixing vessel.

The means for sensing and responsively adjusting flow of respective liquid reagents to the mixing vessel in the aforementioned system may for example comprise flow conduits interconnecting the mixing vessel with the respective liquid reagent sources, with flow control valves disposed in the flow conduits, and pressure sensors operatively arranged to sense pressures of liquid reagents from the respective liquid reagent sources for responsively adjustment of the flow control valves in the respective liquid reagent flow conduits to maintain the predetermined mixed multicomponent liquid composition.

A still further aspect of the invention relates to a mixing and dispensing system for supplying a multicomponent liquid reagent stream, such system comprising:

a reservoir for holding liquid reagents for mixing therein to form multicomponent liquid reagent and for discharging the multicomponent liquid reagent stream;

a pressurizing gas source coupled in gas flow relationship with the reservoir and constructed and arranged for selectively imposing gas pressure on the multicomponent liquid reagent in the reservoir to effect discharge of the multicomponent liquid reagent stream from the reservoir;

a mixing manifold comprising a valve block with multiple liquid inlet ports communicating with valve block passages discharging respective liquid reagents from respective liquid inlet ports into the reservoir;

at least two liquid reagent sources, each coupled in liquid flow relationship to a port of the valve block;

flow control valves respectively disposed in the liquid inlet ports of the valve block; and

means for controllably adjusting the flow control valves in respective liquid inlet ports of the valve block, to selectively adjust the flow control valves for achieving a desired compositional mix of respective liquid reagents in the multicomponent liquid reagent discharged from the reservoir.

Yet another aspect of the invention relates to a mixing and dispensing system for mixing of liquid reagents from respective sources thereof and dispensing of a mixed multicomponent liquid reagent stream, such system comprising:

a multi-position mixing valve coupled in liquid flow relationship to the liquid reagent sources, wherein each position of the multi-position valve couples the valve with a discrete one of the liquid reagent sources, the mixing valve being coupled with a mixing valve discharge for dispensing of the mixed multicomponent liquid reagent stream from the mixing valve; and

means for motively, cyclically and repetitively positioning the valve in different ones of its respective multiple positions in such manner as to mix predetermined flows of respective liquid reagents from the respective sources thereof, to dispense the mixed multicomponent liquid reagent stream from the mixing valve discharge having a predetermined composition.

The mixing valve may for example comprise a two-way cyclic mixing valve, including a housing having a rotary valve element mounted therein for rotation in either of opposing directions to respective ones of the multiple positions. The means for positioning the mixing valve in respective multiple position states thereof may for example comprise a central processing unit operatively coupled to the multi-position mixing valve. The associated system may also comprise means for sensing a liquid characteristic of liquid reagents from the respective sources, and transmitting a corresponding signal to the central processing unit, whereby the mixed multicomponent liquid reagent stream dispensed from the discharge of the mixing valve has a selected liquid characteristic.

In a method aspect, the invention in one embodiment relates to a liquid delivery method, comprising:

providing liquid in a pressurizable holding zone;

imposing a pressurizing gas on the liquid to effect discharge of liquid from the holding zone; and flowing the liquid discharge from the holding zone to a liquid mass flow controller; and

dispensing the liquid after flow through the mass flow controller, as a flow- controlled liquid stream.

Such method may further comprise mixing the flow-controlled liquid stream from the liquid mass flow controller with at least one other liquid, to supply a mixed liquid stream. The method may also further comprise vaporizing the flow-controlled liquid stream, and contacting vapor from vaporization of the flow-controlled liquid stream with a substrate under deposition conditions to deposit a material on such substrate from the vapor.

In another aspect, the invention relates to a method for vapor deposition of material on a substrate wherein the vapor is derived from a multicomponent liquid reagent, such method comprising:

making up the multicomponent liquid reagent by mixing of component liquid reagent streams from respective sources thereof;

vaporizing the multicomponent liquid reagent to form a reagent vapor; and

contacting the reagent vapor with a substrate to deposit said material thereon;

wherein flows of component liquid reagents from their respective sources are controllably adjusted in relation to one another in response to at least one process condition of the respective component liquid reagents.

In a specific aspect, the invention may comprise a liquid reagent delivery and vaporization system including a pressurizable reservoir constructed and arranged to be selectively pressurized when the reservoir contains a reagent liquid during operation of the system. Such construction and arrangement of the reservoir for selective pressurization thereof may include a fluid-tight construction of the reservoir and its coupling to a pressurizing gas source by which pressurized gas is introduced to the reservoir to physically displace the liquid therein so that it egresses from the vessel. A liquid mass flow controller is joined in liquid flow relationship to the pressurizable reservoir in receiving relationship to the pressurized gas-displaced liquid, so that the liquid egresses from the reservoir and flows through the liquid mass flow controller in a controllably metered manner. The liquid then flows from the liquid mass flow controller to the vaporizer for vaporization of the liquid reagent to form reagent source vapor. The source vapor thus formed may then be flowed to a downstream locus, e.g., for chemical vapor deposition, to form a thin film material on a substrate in the CVD reactor.

In another particular embodiment, the invention comprises a reagent liquid delivery system for delivery of a multicomponent source reagent composition. In this embodiment, a mixing manifold and reservoir assembly are provided, in which the reservoir containing reagent liquid is pressurized with suitable pressurizing gas to motively discharge the reagent liquid from the reservoir to a downstream liquid flow control device such as a liquid mass flow controller. The reservoir may be provided with liquid level sensing means so that the reservoir is replenished with reagent liquid components when the liquid level in the reservoir is reduced to a predetermined (set- point) level. The mixing manifold is arranged in a supply relationship to the reservoir, for delivery of the reagent liquid components to the reservoir. The mixing manifold may be provided with suitable high pressure valves to permit maintenance of a desired elevated gas pressure in the reservoir, for delivery of the multicomponent precursor composition to the downstream vaporizer and deposition apparatus, via the flow control device.

The mixing reservoir may be provided with suitable mixing enhancement means, such as diffusers, showerheads, or other flow "spreaders" at the outlets of the mixing manifold which discharge the respective components into the mixing reservoir.

In yet another specific embodiment, the invention comprises a mixing means including a mixing manifold (which may comprise and/or communicate with a mixed liquid volume retention means, such as the mixing reservoir described above). In such liquid delivery system, the mixing manifold is coupled with supply means for the respective liquid components to be mixed in the mixing manifold. A flow controller, such as a liquid mass flow controller, is coupled in flow-receiving relationship to the mixing manifold, to receive the mixed liquid composition therefrom and to discharge the liquid composition at a controlled flow rate. The respective liquid components are delivered to the mixing manifold via supply lines containing controllable valves therein, and such valves are linked to a process control system which is constructed and arranged to control the rate of introduction of the respective liquid components into the mixing manifold. Such process control system may utilize a database, e.g., in a non-volatile memory, for computationally determining the total flow input required for each of the respective precursor components, based on the liquid properties of the respective precursor components. For example, the liquid properties may include thermal (temperature) and viscous properties, which are monitored and utilized to programmably determine the relative amounts of the respective liquid components to be mixed, and to correspondingly control the valves in the lines introducing the respective liquid components to the mixing manifold.

Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of a liquid reagent delivery and vaporization system of the prior art showing a typical apparatus arrangement therefor.

Figure 2 is a schematic representation of a liquid reagent delivery and vaporization system of the present invention, coupled to a chemical vapor deposition reactor.

Figure 3 is a schematic representation of a liquid reagent delivery, vaporization and chemical vapor deposition system according to one embodiment of the present invention.

Figure 4 is a schematic representation of a mixing assembly and flow controller system, according to one embodiment of the invention.

Figure 5 is a schematic representation of a liquid delivery system comprising a diaphragmatic manifold accommodating pressure equalization between respective precursor reagent streams at differing initial pressures.

Figure 6 is a schematic representation of a mixing manifold/reservoir assembly, according to still another embodiment of the invention. Figure 7 is a schematic representation of a mixing and flow control system according to another embodiment of the invention, comprising a two-way cyclic mixing valve, associated liquid supply reservoirs and fluid motive drive means, and a central processing unit for the system.

DETAILED DESCRIPTION OF THE INVENTION. AND PREFERRED EMBODIMENTS THEREOF

The disclosures of the following patents are hereby incorporated herein in their entireties by reference:

U.S. Patent 5,204,314 issued April 20, 1993 to Peter S. Kirlin et al.;

U.S. Patent 5,536,323 issued July 16, 1996 to Peter S. Kirlin et al.; and

U.S. Patent 5,711,816 issued January 27, 1998 to Peter S. Kirlin, et al.

The present invention takes advantage of the fact that the liquid mass flow controller is a much more passive device in flow metering than is the positive displacement liquid pump. The liquid flow stream associated with a liquid mass flow controller is much less turbulent and the flow controller does not "push" or "pull" the liquid as does the positive displacement pump. The liquid mass flow controller simply meters the flow and opens or closes a valve accordingly to increase or decrease liquid flow to match the selected set point for the device.

Liquid mass flow controllers are physically robust, reliable and highly maintenance-free in character. They are capable of sustained continuous operation without deterioration or malfunction.

In order for the composition of a multicomponent vapor to be strictly controlled when the liquid delivery and vaporization system of the invention is employed for the delivery and vaporization of plural liquid components supplied from individual discrete liquid reservoirs, it may be desirable to deploy a mixing means, e.g., a static mixer-containing chamber receiving the plural streams from the associated liquid reservoirs via their respective liquid mass flow controllers, or a mechanical mixer-containing chamber, or other mixing means, whereby the plural liquid streams from the various liquid mass flow controllers is homogeneously blended to produce the multicomponent liquid source reagent for vaporization yielding a corresponding homogeneous vapor for subsequent process usage.

Referring now to the drawings, Figure 1 is a schematic representation of a liquid reagent delivery and vaporization system 10 of the prior art showing a typical apparatus arrangement therefor.

In this prior art scheme, a liquid reagent reservoir 12, containing liquid reagent 14, is joined in flow communication with a source 18 of nitrogen or other inert gas by conduit 16 containing flow control valve 20 therein. Liquid reagent is motively withdrawn by means of the positive displacement pump 28 from the reservoir 12 in line 22 and flowed into the mixing manifold 24. The mixing manifold may be fed with reagent liquids from other reservoirs similarly arranged, with respect to the single reservoir illustrated in Figure 1.

Mixed reagent then is flowed in line 26 to the positive displacement pump 28 and is discharged therefrom in line 30, and passed through the pulse damper 32 (to attenuate surges in the flow of the reagent stream) to the vaporizer 36 via line 34. The vaporizer may also receive oxidant or inert carrier gas in line 38 from a suitable source of same (not shown). The vaporizer may be constructed and arranged in any suitable manner, to vaporize the liquid reagent and form reagent vapor.

The reagent vapor, augmented with any oxidant or carrier gas to form a reagent vapor stream, flows in line 40 to the chemical vapor deposition (CVD) chamber 42, in which deposit of the deposition species on a substrate is carried out in a conventional manner to form the desired thin film on the substrate. Effluent gas is discharged from the CVD chamber in line 44 and may be passed to further processing or disposition.

Figure 2 is a schematic representation of a liquid reagent delivery and vaporization system 110 of the present invention, coupled to a chemical vapor deposition reactor 142.

In the Figure 2 system as schematically shown, the corresponding elements of the process system are numbered correspondingly to the same elements in the Figure 1 system, by addition of 100 to the numbers of the same elements of Figure 1. In place of the mixing manifold, positive displacement pump and pulse damper of the Figure 1 system, the Figure 2 arrangement utilizes a liquid mass flow controller 150 conducting liquid directly from the reagent reservoir 112 in lines 122 and 134 to the vaporizer 136. The pressurizing gas source in the Figure 2 system, in contrast to the Figure 1 system, is utilized to provide the motive force on the liquid, and thus may be constructed and arranged to impress a substantially higher pressure on the liquid than in the Figure 1 system, where only a relatively low superatmospheric pressure is applied to the liquid, below that necessary to impel the liquid to flow through the flow circuit of the system. The liquid mass flow controller may be of any appropriate commercially available type, e.g., a Liqui-Flow liquid mass flow controller, commercially available from Porter Instrument Company, Inc.

The apparatus of Figure 2 may be employed to variously handle neat liquids, solutions, and/or liquid reagent "cocktails," i.e., a solution which contains multiple solvents and solutes.

Figure 3 is a schematic representation of a liquid reagent delivery, vaporization and chemical vapor deposition system 160 according to another embodiment of the present invention.

The system 160 comprises a liquid reagent reservoir 162, containing a first liquid reagent 164, which is joined in flow communication with a source 166 of pressurized nitrogen or other inert gas by conduit 168 containing flow control valve 170 therein. Liquid reagent is flowed in line 172 to the liquid mass flow controller 174 and flowed in metered fashion by such device for discharge in line 176 to mixing chamber 180. A liquid reagent reservoir 182, containing a second liquid reagent 184, is joined in flow communication with a source 188 of pressurized nitrogen or other inert gas by conduit 188 containing flow control valve 190 therein. Liquid reagent is flowed in line 192 to the liquid mass flow controller 194 and flowed in metered fashion by such device for discharge in line 196 to mixing chamber 180.

In the mixing chamber 180, the first and second liquid reagents are blended to achieve homogeneity thereof. The resulting multicomponent liquid reagent is flowed in line 198 to the vaporizer 200. The vaporizer 200 may also receive oxidant or inert carrier gas in line 202 from a suitable source of same (not shown). The vaporizer may be constructed and arranged in any suitable manner, to vaporize the liquid reagent and form reagent vapor.

The reagent vapor, augmented with any oxidant or carrier gas to form a reagent vapor stream, flows in line 204 to the chemical vapor deposition (CVD) chamber 206, in which deposit of the deposition species on a substrate is carried out in a conventional manner to form the desired thin film on the substrate. Effluent gas is discharged from the CVD chamber in line 208 and may be passed to further processing or disposition.

Figure 4 is a schematic representation of a mixing manifold and flow control assembly, according to one embodiment of the present invention. The illustrated system 300 comprises a mixing manifold 302 joined in liquid flow communication with respective precursor component reservoirs 304, 306, 308 and 310.

The precursor component reservoir 304 is connected to the mixing manifold 302 by means of precursor feed line 312 having sensor assembly 314 and controllable flow valve 316 therein, as shown. The precursor component reservoir 306 is similarly arranged with respect to precursor feed line 318, sensor assembly 320 and controllable flow valve 322. In like manner, reservoir 308 has associated therewith precursor feed line 324, sensor assembly 326 and controllable flow valve 328, and reservoir 310 is associated with precursor feed line 330, sensor assembly 332 and controllable flow valve 334. Each of the respective precursors from the reservoirs 304, 306, 308 and 310 are introduced into the mixing manifold 302 for mixing therein. The mixing manifold 302 is coupled by conduit 336 to the flow controller 338, e.g., a liquid mass flow controller of a type previously described herein. The flow controller 338 discharges a controlled rate flow of the mixed precursor composition in line 340 to the vaporizer 342, with the resulting source reagent vapor then being flowed in line 344 to CVD reactor 346, from which waste gas is discharged during operation in line 348.

The controllable flow valves 316, 322, 328 and 334 each comprise an actuatable valve element and corresponding actuator/controller means for opening or closing of the valve element in a controllable fashion. The controllable flow valves are controlled by a central processor 350, which may, for example, comprise microprocessor or other computer hardware, software, and/or firmware, preferably including a non-volatile memory which contains liquid property information, including for example thermal, viscous and other properties, the specific characteristics being selectable from a wide variety of possible parameters for the precursor streams being introduced to the mixing manifold 302 in operation of the system.

The central processor 350 is linked by sensor lines 352, 354, 356 and 358 to respective precursor flow sensors 314, 320, 332 and 326, so that a separate sensor is arranged in sensing relationship to each of the precursor streams. The sensor may monitor any suitable process variable, such as thermal properties, viscous properties, etc., with such sensed property information being conveyed from the sensor means via the corresponding signal transmitting lines 352, 354, 356 and 358 to the central processor 350. The central processor is correspondingly programmed to actuate each of the respective controllable flow valves, with control signal transmission lines 360, 362, 364 and 366 respectively conveying control signals to controllable flow valves 328, 334, 316 and 322, to maintain the sensed variables or resulting flow rate, composition, or other controlled (output) variables at a desired set point value or within allowable set point limits.

By this arrangement, the composition of the mixed precursor composition may be selectively controlled or varied, to maintain an appropriate precursor composition in the mixed stream flowed by the flow controller 338 in line 340 to the vaporizer 342.

Thus, the central processor controllably operates the system to provide a desired source composition for the source reagent vapor, so that the corresponding vapor is effectively utilized to produce films in the deposition chamber 346 which are stoichiometrically controlled within close compositional tolerances.

Additionally, although not illustrated, the mixing manifold could be selectively coupleable to more than one flow controller 338, with the mixed precursor composition being selectively divertable to one of the multiple flow controllers, depending on the flow rate desired for a given vaporization and deposition process. Such arrangement takes advantage of the fact that flow controllers may be optimized over a specific flow range. Thus, for example, flow controllers may be employed, with a first flow controller having a flow range such as 0.01 to 1 milliliters per minute, with a second flow controller having a flow range of from 0.1 to 10 milliliters per minute, etc. In another embodiment, a single system of reservoirs with a mixing manifold may be configured to supply flow controllers for vaporizers at different CVD reactors, such as would be found in a manufacturing plant, analogous to central plumbing of another consumable liquid or gas.

Figure 5 is a schematic representation of a mixing and liquid delivery system 400, comprising a mixing manifold 402 which is joined via a supply manifold 404 to precursor reservoirs 406, 408, 410 and 412, as shown.

The supply manifold 404 comprises a first manifold segment 414 communicating with precursor feed line 416 joined to reservoir 406. A second segment 418 of the supply manifold is joined to precursor feed line 420, third supply manifold segment 422 is joined to precursor feed line 424 and fourth supply manifold segment 426 is joined to precursor feed line 428. Disposed between the respective segments of the supply manifold are diaphragm elements 430, 432, 434 and 436. Each of these diaphragm elements is disposed in the interior volume of the supply manifold 404, to separate adjacent segments of the supply manifold from one another, so that no mixing between adjacent segments takes place. Thus, the diaphragm element constitutes a mixing barrier, but the diaphragm element is dynamically displaceable in response to the variation of pressure in precursor streams on either side, so that the diaphragm element deforms in response to the greater of the pressures on its respective faces, and so that pressure is equalized in the supply manifold 404 by such diaphragm element displacement.

By such arrangement, variation in the pressure of the constituent streams is dynamically adjusted in the supply manifold to equalize pressure and thereby avoid perturbations to or deviations in the composition of the mixed precursor composition produced by the mixing manifold. The mixed precursor composition is flowed from the mixing manifold 402 in conduit 440 to flow controller 442 which may, for example, comprise a liquid mass flow controller of previously described type, and which delivers a metered flow of the mixed precursor composition in line 444 to the vaporizer/CVD complex 446, from which waste vapor is discharged in line 448.

As an alternative to the passive pressure and flow equalization structure illustrated in the embodiment of Figure 5, the differences in pressure of respective precursor feed components may be accommodated with an active control scheme including flow control valves in the various precursor feed lines at the inlet to the mixing manifold, whereby differences in pressure may be sensed, as for example, by a type of control arrangement as shown in Figure 4, with such pressure sensing being used to responsively actuate controllable flow valves to adjust the respective flows of the precursor components to the mixing manifold, so that the composition of the mixed precursor composition ultimately discharged from the mixing manifold is maintained within acceptable compositional limits.

As a still further alternative, and as shown in Figure 5, the previously described system illustrated may in lieu of pressure-deformable diaphragm elements feature pressure taps 430, 432, 434 and 436 (the same elements previously described for purposes of illustration being taken as pressure taps instead of pressure-deformable diaphragm elements), which are joined by pressure signal transmission lines 452, 454, 456 and 458 to the central processing unit 460. The central processing unit 460 determines from the relative pressure sensings the amount of each of the liquid feed materials that should properly be fed to the mixing manifold for the desired mixed liquid composition.

Thus, the central processing unit 460 responsively sends a first control signal in signal transmission line 462 to the actuator assembly 464 comprising a pressurized gas which is directed at appropriate flow rate by the actuator assembly in line 466 to the liquid reservoir 406, to displace the liquid therefrom into feed line 416 for flow to the mixing manifold 402.

In like manner, and simultaneously, the central processing unit 460 responsively sends a second control signal in signal transmission line 468 to the actuator assembly 470 comprising a pressurized gas which is directed in line 472 at appropriate flow rate by the actuator assembly to the liquid reservoir 408, to displace the liquid therefrom into feed line 420 for flow to the mixing manifold 402.

Further, in like manner, and simultaneously, the central processing unit 460 responsively sends a third control signal in signal transmission line 474 to the actuator assembly 476 comprising a pressurized gas which is directed in line 478 at appropriate flow rate by the actuator assembly to the liquid reservoir 410, to displace the liquid therefrom into feed line 424 for flow to the mixing manifold 402.

Finally, in like manner, and simultaneously, the central processing unit 460 responsively sends a fourth control signal in signal transmission line 480 to the actuator assembly 482 comprising a pressurized gas which is directed in line 484 at appropriate flow rate by the actuator assembly to the liquid reservoir 412, to displace the liquid therefrom into feed line 428 for flow to the mixing manifold 402.

By this arrangement, the system is controllably operated to transmit to the mixing manifold 402 a precisely measured amount of each of the respective feed liquid streams, so that the mixed liquid in line 440 discharged from the mixing manifold to the flow controller 442 is of the desired composition.

The present invention thus contemplates the control of multiple precursor feed streams to a mixing manifold, in which the respective streams may be selectively, independently controlled by a central processor. Such central processor may contain data for a number of precursor liquid compositions, which can be accessed by a user of the central processor, to controllably adjust the rates of introduction of various precursors, or precursor components (such as individual solvents of a multicomponent solution), so that a mixed precursor composition is controllably formulated in situ at the locus of the process system carrying out vaporization of the precursor composition for the subsequent formation of a deposited film from the thus- produced vapor.

To achieve precise control of precursor components, as formulated to yield a mixed precursor composition, the controllable flow valves associated with the respective precursor component streams may be cycled according to a predetermined or otherwise selected timing sequence, so that the valves of the system open and close many times during a measurement cycle to ensure that the flow sensor looks at a liquid stream with the appropriate composition, and to avoid errors in measurement and control. The timing sequence and specific arrangement of sensing and control elements may be widely varied within the skill of the art, and is readily determinable without undue experimentation by those of ordinary skill in the field of the invention.

In the practice of the invention utilizing a mixing manifold and flow sensor, sufficient volume needs to be provided for complete mixing of the incoming streams, and various means may be employed to induce turbulence in the mixed volume or otherwise to improve mixing therein.

Figure 6 is a schematic representation of a mixing manifold/reservoir assembly 500, according to another embodiment of the invention. The mixing manifold/reservoir assembly 500 comprises a mixing manifold 502 including a valve block 504 with respective liquid inlet ports 506, 508, 510 and 512, which are coupled to supply means for precursor components, such means, for example, comprising a suitable tank and connecting conduit(s), so that the liquid precursor component is delivered to the valve block, and flowed in metered fashion into the mix reservoir 514.

A pressurizing gas from gas source 516 pressurizes the mix reservoir 514. The pressurizing gas is flowed in line 518 to feed conduit 520, from which the pressurizing gas enters the interior volume of the mix reservoir 514. The mix reservoir 514 may be provided with a liquid level sensor 522, for monitoring the level of liquid in the mix reservoir and responsively opening or closing the valves in valve block 504 to adjust the liquid volume in the mix reservoir to a desired level.

The valve elements 524 in the valve ports 526 of valve block 504 may be suitably coupled with respective valve actuators 530. Each actuator is provided with a valve seal 532 and is connected by power line 534 to suitable power supply means (not shown for clarity). Only a single valve actuator is shown in Figure 6, it being understood that each of the valve elements in the respective ports of the valve block are correspondingly associated with a separate valve actuator therefor.

In the interior volume of the mix reservoir 514, the respective introduced precursor components are mixed with one another. The resulting mixed precursor composition then is flowed in discharge conduit 536 from the reservoir and through the valve block for discharge therefrom in line 538, for subsequent passage to downstream processing means, e.g., vaporizer and chemical vapor deposition apparatus.

To assist the mixing of precursor components in the mix reservoir 514, the discharge conduit 536 may be provided in a lower interior portion thereof with a mixing enhancement 538, such as a static mixer, turbulator, or like structure, so that the liquid discharged from the assembly in line 538 is of a desired homogeneous character. Additionally, or alternatively, other mixing means may be employed, such as a magnetically coupled stirring element disposed in the interior of the mix reservoir and operatively translated by exteriorly magnetically coupled drive means. Further, the discharge ports in the valve block, from which the introduced precursor liquid is discharged to the interior volume of mix reservoir 514, may be provided with flow dispersing means, to facilitate interspersion of the respective precursor components introduced from the valve block to the mix reservoir.

Figure 7 is a schematic representation of a mixing and flow control system 600 according to another embodiment of the invention, comprising a two-way cyclic mixing valve 602, valve switching actuator 603, associated pressurized liquid supply reservoirs 604 and 606, and a central processing unit 608 for the system.

The two-way cyclic mixing valve 602 comprises a housing 610 having a rotary valve element 612 mounted therein for rotation in the direction indicated by bidirectional arrow Y on valve shaft 614. The rotary valve element 612 has a flow passage 616 therein, which in the illustrated position of the valve element 612 is registered at one end of the passage with liquid supply line 620 coupled with pressurized liquid reservoir 604, and at the other end of the passage is registered with the mixed liquid discharge line 622.

Upon rotation of the valve element 612 to the position shown in dashed line representation in Figure 7, the valve element 612 is registered at one end of the passage with liquid supply line 624 coupled with pressurized liquid reservoir 606, and at the other end of the passage is registered with the mixed liquid discharge line 622. Thus, in the dashed line position, the valve element has been rotated by 90° relative to the position of the passage 616 shown in solid line representation in Figure 7.

The pressure and composition of the liquid in each of the reservoirs 604 and 606 may be monitored and the system responsively actuated to switch the valve element 612 between the respective positions thereof in a cyclic repeating manner to effect mixing and introduction of the liquids from the pressurized reservoirs so that the liquid discharged in the discharge line 616 is of a selected pressure, flow rate and compositional character. This is effectuated by the sensing of the pressurized liquid in reservoir 604 as to the relevant pressure and/or compositional characteristics thereof, with a corresponding sensing signal being passed in line 626 to the central processing unit 608, and concurrent sensing of the pressurized liquid in reservoir 606 as to the relevant pressure and/or compositional characteristics thereof, with a corresponding sensing signal being passed in line 628 to the central processing unit 608, and concurrent sensing of the pressurized liquid in discharge line 622 as to the relevant pressure thereof, with a corresponding signal being passed in line 634 to the central processing unit 608. The respective liquid characteristic sensing signals are processed in the central processing unit 608, and a control output signal is generated by the unit which is passed in signal transmission line 630 to the valve element controller 603. The valve element controller 603 is in turn connected by mechanical coupling 632 to the stem 614 of the rotary valve element, which at suitable rapid switching rate cyclically switches the valve element between a first position as illustrated in which the valve element passage 616 communicates with lines 620 and 622, and the second position in which the valve element passage 616 communicates with lines 624 and 622.

The central processing unit operates according to a selected algorithm, to provide the desired flow rate, pressure and composition to the mixed liquid in line 622, which becomes mixed "in situ" in line 622 by the rapidly cycling valve element, so that small amounts of the respective liquids are dispensed to the discharge line 622 as the valve element is rapidly switched from introducing the liquid from reservoir 604 to introducing the liquid from reservoir 606 into the discharge line, followed by switching of the valve to repeat the sequence, so that the valve element 612 is alternately and repetitively switched between the first and second positions of the valve element, in a cycle which is dependent on the algorithm utilized by the central processing unit 608. By this arrangement, the mixing valve can accommodate time- varying pressure differentials between the respective liquid feed streams and the discharge line, thereby producing a desired concentration and flow rate in the liquid ultimately discharged from line 622 downstream of the mixing valve.

It will be recognized that the system shown in Figure 7 may be varied to accommodate more than two feed liquid streams, the number of streams being dependent on the final output mixed liquid stream desired to be produced in operation of the system. Thus, a system comprising three liquid feed streams may be operated with a three position valve, a system with four liquid feed streams may be operated with a four position valve, etc., with the algorithm being properly modified to accommodate the specific number of streams employed so that the desired mixing operation is carried out to produce a predetermined mixed liquid stream, of appropriate desired pressure, flow rate and composition. INDUSTRIAL APPLICABILITY

The apparatus and method of the invention have utility for the formation of thin films, layers and coatings on substrates, in end use applications such as the manufacture of microelectronic devices and structures generally, as well as in nanotechnology applications. In these implementations, the invention provides close control of film morphology, composition, and stoichiometry. The invention thus has utility for forming films of refractory materials such as for example: high temperature superconducting (HTSC) materials; ferroelectric materials useful in applications such as infrared detectors and thin film capacitors well as filters and phase shifters; photonic materials useful in applications such as optical switching, holographic memory storage, and sensors; materials useful for scintillation detecting and coating of optical fibers; thin-film materials for high density memory devices; buffer layers for interfacing between substrates and overlayers; and materials for monolithic integrated circuits on silicon substrates.

Claims

THE CLAIMS

1. A liquid delivery system, comprising:

a pressurizable reservoir for holding a liquid;

a pressurizing gas source coupled with said reservoir and constructed and arranged to selectively impose a pressure on liquid therein to effect discharge of liquid from the reservoir; and

2. A liquid delivery system according to claim 1, wherein the reservoir comprises a fluid-tight vessel coupled to the pressurizing gas source.

3. A liquid delivery system according to claim 1, further comprising mixing means joined in liquid flow relationship to the liquid mass flow controller for receiving the flow-controlled liquid stream therefrom, with a source of at least one other liquid joined in liquid flow relationship to the mixing means, for mixing the liquids introduced thereto and discharging a mixed liquid stream.

4. A liquid delivery system according to claim 3, wherein said mixing means comprises a mixing element selected from the group consisting of mixing vessels, mixing valves and mixing manifolds.

5. A liquid delivery system according to claim 3, wherein said source of at least one other liquid comprises a second pressurizable reservoir for holding a second liquid, and a second pressurizing gas source coupled with the second reservoir to impose a pressure on the liquid therein to effect discharge of liquid from the second reservoir to the mixing means.

6. A liquid delivery system according to claim 3, wherein said mixing means comprise a mixing vessel.

7. A liquid delivery system according to claim 6, further comprising mixing enhancement means in the mixing vessel.

8. A liquid delivery system according to claim 3, wherein the liquids are delivered from the respective reservoirs to the mixing means by supply lines, with flow control valves in said supply lines, and a process control system operatively associated with and constructed and arranged to control said flow control valves to effect a predetermined rate of introduction of the respective liquids to the mixing means.

9. A liquid delivery system according to claim 8, wherein the process control system utilizes a database for computationally determining flows of the respective liquid reagents required, for make-up of the mixed liquid stream.

10. A liquid delivery system according to claim 9, wherein the database comprises liquid properties, said system further comprising means for monitoring the liquids introduced to the mixing means for at least of one said liquid properties comprised in said database, and responsively controlling the flow control valves to effect mixing of said liquids in desired proportions in said mixing means.

11. A liquid delivery and vaporization system, comprising:

a pressurizable reservoir for holding a liquid;

a pressurizing gas source coupled with said reservoir and constructed and arranged to selectively impose a pressure on liquid therein to effect discharge of liquid from the reservoir;

a liquid mass flow controller joined in liquid flow relationship to the reservoir for receiving the liquid discharged therefrom, and for dispensing the liquid after flow through the mass flow controller, as a flow-controlled liquid stream; and

a vaporizer receiving the flow-controlled liquid stream for vaporization thereof to form a vapor.

12. A liquid delivery and vaporization system according to claim 11, wherein the reservoir comprises a fluid-tight vessel coupled to the pressurizing gas source.

13. A liquid reagent delivery and vaporization system according to claim 11, further comprising mixing means joined in liquid flow relationship to the liquid mass flow controller for receiving the flow-controlled liquid stream therefrom, with a source of at least one other liquid joined in liquid flow relationship to the mixing means, for mixing the liquids introduced thereto and discharging a mixed liquid stream.

14. A liquid delivery and vaporization system according to claim 13, wherein said mixing means comprises a mixing element selected from the group consisting of mixing vessels, mixing valves and mixing manifolds.

15. A liquid delivery and vaporization system according to claim 13, wherein said source of at least one other liquid comprises a second pressurizable reservoir for holding a second liquid, and a second pressurizing gas source coupled with the second reservoir to impose a pressure on the liquid therein to effect discharge of liquid from the second reservoir to the mixing means.

16. A liquid delivery and vaporization system according to claim 13, wherein said mixing means comprise a mixing vessel.

17. A liquid delivery and vaporization system according to claim 16, further comprising mixing enhancement means in the mixing vessel.

18. A liquid delivery and vaporization system according to claim 13, wherein the liquids are delivered from the respective reservoirs to the mixing means by supply lines, with flow control valves in said supply lines, and a process control system operatively associated with and constructed and arranged to control said flow control valves to effect a predetermined rate of introduction of the respective liquids to the mixing means.

19. A liquid delivery and vaporization system according to claim 18, wherein the process control system utilizes a database for computationally determining flows of the respective liquid reagents required, for make-up of the mixed liquid stream.

20. A liquid delivery and vaporization system according to claim 19, wherein the database comprises liquid properties, said system further comprising means for monitoring the liquids introduced to the mixing means for at least of one said liquid properties comprised in said database, and responsively controlling the flow control valves to effect mixing of said liquids in desired proportions in said mixing means.

21. A liquid delivery, vaporization and deposition system, comprising:

a pressurizable reservoir for holding a liquid;

a liquid mass flow controller joined in liquid flow relationship to the reservoir for receiving the liquid discharged therefrom, and for dispensing the liquid after flow through the mass flow controller, as a flow-controlled liquid stream;

a vaporizer receiving the flow-controlled liquid stream for vaporization thereof to form a vapor; and

means for receiving said vapor and depositing material on a substrate therefrom.

22. A system according to claim 21, wherein said means for receiving said vapor and depositing material on a substrate therefrom comprise a vapor deposition chamber constructed and arranged to contain the substrate therein for contacting of the substrate with the vapor to effect deposition of material thereon.

23. A system according to claim 21, wherein said means for depositing material from the reagent vapor on a substrate comprises a CVD reactor joined in vapor- receiving relationship to the vaporizer.

24. A liquid reagent delivery system for delivering a multicomponent reagent material from independent liquid reagent sources from which the individual reagents may vary in pressure relative to one another, said liquid reagent delivery system comprising a supply manifold coupled in supply relationship to the respective liquid reagent sources, said supply manifold being physically divided into discrete segments by pressure-deformable separation elements, and with each segment of the supply manifold being arranged to discharge to a mixing means, said pressure-deformable separation elements being responsively deformable to pressure so that volume of respective segments of the supply manifold are dynamically allocated in response to pressure, to equalize the pressure in the supply manifold, and thereby accommodate pressure variation of the respective liquid reagents flowed to the supply manifold.

25. A liquid reagent delivery system including a mixing vessel receiving respective liquid reagents from sources thereof coupled in flow relationship to the mixing vessel, for discharge of a mixed multicomponent liquid from the mixing vessel, wherein pressure of the respective liquid reagents is independently variable at the respective sources thereof, comprising means for sensing pressure of each liquid reagent and responsively adjusting flow of the respective liquid reagents to maintain a predetermined composition of the mixed multicomponent liquid discharged from the mixing vessel.

26. A system according to claim 25, wherein the means for sensing and responsively adjusting flow of respective liquid reagents to the mixing vessel comprise flow conduits interconnecting the mixing vessel with the respective liquid reagent sources, with flow control valves disposed in the flow conduits, and pressure sensors operatively arranged to sense pressures of liquid reagents from said respective liquid reagent sources and responsively adjusting the flow control valves in the respective liquid reagent flow conduits to maintain said predetermined mixed multicomponent liquid composition.

27. A mixing and dispensing system for supplying a multicomponent liquid reagent stream, said system comprising:

a pressurizing gas source coupled in gas flow relationship with the reservoir and constructed and arranged for selectively imposing gas pressure on the multicomponent liquid reagent in the reservoir to effect discharge of the multicomponent liquid reagent stream from the reservoir; a mixing manifold comprising a valve block with multiple liquid inlet ports communicating with valve block passages discharging respective liquid reagents from respective liquid inlet ports into the reservoir;

means for controllably adjusting the flow control valves in respective liquid inlet ports of the valve block, to selectively adjust the flow control valves for achieving a desired compositipnal mix of respective liquid reagents in the multicomponent liquid reagent discharged from said reservoir.

28. A system according to claim 27, further comprising a mixing enhancement in the vessel.

29. A system according to claim 28, wherein said mixing enhancement is selected from the group consisting of static mixers, turbulators, and magnetically coupled stirring elements.

30. A mixing and dispensing system for mixing of liquid reagents from respective sources thereof and dispensing of a mixed multicomponent liquid reagent stream, said system comprising:

a multi-position mixing valve coupled in liquid flow relationship to said liquid reagent sources, wherein each position of the multi-position valve couples the valve with a discrete one of said liquid reagent sources, said mixing valve being coupled with a mixing valve discharge for dispensing of the mixed multicomponent liquid reagent stream from the mixing valve; and

means for motively, cyclically and repetitively positioning the valve in different ones of its respective multiple positions in such manner as to mix predetermined flows of respective liquid reagents from said respective sources thereof, to dispense the mixed multicomponent liquid reagent stream from said mixing valve discharge having a predetermined composition.

31. A system according to claim 30, wherein the mixing valve comprises a two- way cyclic mixing valve, including a housing having a rotary valve element mounted therein for rotation in either of opposing directions to respective ones of said multiple positions.

32. A system according to claim 30, wherein said means for positioning the mixing valve in respective multiple position states thereof comprise a central processing unit operatively coupled to the multi-position mixing valve.

33. A system according to claim 32, further comprising means for sensing a liquid characteristic of liquid reagents from the respective sources, and transmitting a corresponding signal to the central processing unit, whereby the mixed multicomponent liquid reagent stream dispensed from the discharge of the mixing valve has a selected liquid characteristic.

34. A liquid delivery method, comprising:

providing liquid in a pressurizable holding zone;

imposing a pressurizing gas on the liquid to effect discharge of liquid from the holding zone; and

flowing the liquid discharge from the holding zone to a liquid mass flow controller; and

35. A method according to claim 34, further comprising mixing the flow- controlled liquid stream from the liquid mass flow controller with at least one other liquid, to supply a mixed liquid stream.

36. A method according to claim 34, further comprising vaporizing the flow- controlled liquid stream.

37. A method according to claim 36, further comprising contacting vapor from vaporization of the flow-controlled liquid stream with a substrate under deposition conditions to deposit a material on such substrate from said vapor.

38. A method for vapor deposition of material on a substrate wherein the vapor is derived from a multicomponent liquid reagent, said method comprising:

vaporizing the multicomponent liquid reagent to form a reagent vapor; and

contacting the reagent vapor with a substrate to deposit said material thereon;