WO1998055668A1

WO1998055668A1 - Method and apparatus for vapor generation and film deposition

Info

Publication number: WO1998055668A1
Application number: PCT/US1998/011090
Authority: WO
Inventors: James J. Sun; Benjamin Y. H. Liu
Original assignee: Msp Corporation
Priority date: 1997-06-02
Filing date: 1998-06-01
Publication date: 1998-12-10
Also published as: JP2002502465A; DE19882473T1

Abstract

A vapor generator (19, 62) and connected chemical vapor deposition chamber (28) for providing a vapor for operation such as chemical vapor deposition has an atomizer (16, 16A, 38, 50) for forming an aerosol or droplet spray (36, 58, 74, 80) separate from a vaporization chamber (19, 62). The aerosol is passed into a heated vaporization chamber (19, 62) wherein the particles or droplets are flash vaporized and larger droplets are vaporized by direct contact with heated surfaces. The resulting gas/vapor stream is then used for chemical vapor deposition, in a separate chemical vapor deposition chamber (26). The vapor and gas stream is preferably passed through a restricted passageway (22, 44, 68) for mixing before being introduced into the chemical vapor deposition chamber (26).

Description

ETHOD AND APPARATUS FOR VAPOR GENERATION AND FILM DEPOSITION

BACKGROUND OF THE INVENTION

This invention relates to a vaporizer for vapor generation for chemical vapor deposition and related applications. The vaporizer may also be used wherever a vapor generator for the precise and controlled delivery of vapor is needed.

In chemical vapor deposition, source vapors are commonly used as reagents to react with substrate surfaces to form thin films on the substrate. The main advantage of using source vapors is the ease and precision with which vapor flow rate can be controlled. The main limitation is that not all the reagents can be easily stored in vapor form at ambient temperatures. Some reagents such as BST (barium strontium titanate) , SBT (strontium bismuth tantalum) , can be much more easily prepared in liquid form at normal temperature with the addition of solvent. Methods of chemical vapor deposition (CVD) that vaporize a liquid source to generate a source gas are therefore preferred for CVD deposition of materials such as BST, SBT, and similar reagents .

One common method used to generate vapor for chemical vapor deposition is to bubble a gas through a heated liquid reagent. As the gas bubbles through the liquid, it is saturated with the reagent vapor. The vapor is then carried by the gas flow to a chamber for deposition. The bubbler generally works well with a pure reagent in liquid form, but is unsuitable for vaporizing materials for BST and SBT deposition. The reagent used for BST and SBT film deposition usually must be dissolved in a solvent and then vaporized. When such a liquid solution is vaporized in a bubbler, the solvent will evaporate more quickly because of its higher volatility. This will cause the concentration of the reagent material in the liquid solution to increase with time. The output vapor quality from the bubbler, therefore, will change with time, causing difficulty in controlling the deposition rate, and the thickness of the film produced. Another disadvantage is the thermal decomposition of the reagents in the bubbler due to the direct contact of the reagent liquid with the heated surface of the bubbler. This premature decomposition may cause variations in the composition in the deposited films • and poor reproducibility in film stoichiometry between different CVD deposition runs. Other disadvantages include the large size of the bubbler and a very rapid change in vaporization rate with operating temperature. Very precise temperature control of the bubbler, therefore, is required.

Patents US-A-5361800 and US-A-5371828 to Ewing disclose a vaporizer including a heater assembly in thermal contact with a stack of thermally conductive, thin, flat disks biased together with a spring-loaded anvil. A heater assembly heats the disks to a temperature in excess of the flash point of the liquid at the process pressure. Liquid is supplied from a pumping system through a tube passing through the center of the coaxial stacked disks and is forced between the parallel disks, against the bias of the spring-loaded anvil . The liquid is heated by the hot surfaces of the disks to a temperature above its flash point and is vaporized. During vaporization, the liquid forms a thin film on the disk surfaces. Increased vaporization surfaces are obtained by using multiple disks. In his method, Ewing uses at least two disk sizes. A liquid film is established on at least a portion of the surfaces of the larger diameter disk for accelerating the vaporization of the liquid.

US-A-5536323 to Kirlin et al . describes a method of delivering an involatile reagent in gaseous form where the involatile reagent source liquid is flash vaporized on a vaporization matrix structure at elevated temperature . The vaporizer comprises a reservoir for supplying an involatile reagent source liquid and a flash vaporization matrix structure. The flash vaporization matrix structure may take the form of a screen, a porous sintered material body or a grid. The

^' flash vaporization matrix structure desirably has at least a 4:1 surface to volume ratio. Both the approach of Ewing and that of Kirlin et al . involve direct contact of a liquid with a heated surface (heated disks in the case of Ewing' s patents and screen, porous sintered material or a grid in the case of Kirlin' s patent) to cause flash vaporization of the reagent. High vaporization rate requires the use of high temperature surfaces, which can cause thermal decomposition of the reagent liquid which comes in contact with the heated surface.

It would be difficult to achieve uniform temperature distribution on all surface areas of all disks using the Ewing disclosure. The disks close to the heat source will have higher temperature than the ones farther away from the heat source due to poor heat conduction through thin disks. Also, in Ewing, the liquid is fed through the path inside of the heating block, where the highest temperature occurs. When the heating block temperature is set at the desired vaporization temperature, the temperature on the surfaces of the disks will be much lower because of conductive and convective heat loss during heat transfer from the heating block to the heating disks. In order to achieve proper temperature at the surfaces of the heating disks, especially for the disks far away from the heat source, the heating block must be operated at a much higher temperature, which contributes to increased thermal decomposition or degradation of the reagent liquid. The liquid path may be clogged, or at least partially clogged, over time, resulting in variations in vapor output and vapor quality.

Similar problems also exist in Kirlin' s vaporizer. It is difficult to achieve uniform temperature distribution on all surface areas of the flash vaporization matrix structure. It is also difficult to deliver liquid to all surface of the flash vaporization matrix structure. The temperature of the surfaces contacting the liquid will suddenly drop when the liquid vaporizes due to energy transfer from the heating surface to the vapor. However, the temperature of the heating surfaces not contacting the liquid will increase due to continuous heat transfer from the heat source to the surface. Another problem exists when it is desired to achieve a large surface to volume ratio of the matrix structure. To achieve a large ratio, the void space in the vaporization matrix must be small. A small void space will increase the risk of clogging as the liquid or vapor thermally decomposes on the heated surface of the matrix with which it comes in contact . As a result, only a moderate surface to volume ratio of the vaporization matrix, in the order of 4:1, can be achieved.

Another approach to achieve flash vaporization of liquid is described in US-A-5547708 to Asaba et al . The reagent liquid is forced through a small orifice in a plate, which is vibrated by a piezoelectric transducer at a known frequency. The reagent liquid is broken up into droplets. The droplet stream then impinges on heated metal disks and is flash vaporized to form vapor. A carrier gas is simultaneously admitted into the vaporizer to carry the vapor into the CVD chamber. There are several potential problems with this particular approach to liquid vaporization. Small drop size is conducive to rapid vaporization of the drop because of the large surface to volume ratio of the liquid drop. This requires the use of small orifices, which may restrict the rate of liquid delivery to the disk, hence the vaporization rate. Small orifice can also become easily clogged, leading to operational problems due to orifice clogging and blockage by contaminant particles in the supply liquid. On the other hand, a large orifice will result in large drop size. The large drop size in turn requires long vaporization time, causing liquid drops hitting the disk to accumulate at the bottom of the disk where it will remain in contact with the heated surface for long periods to cause thermal decomposition or degradation of the reagent liquid.

The method and apparatus described in the present application for vaporization and thin film deposition using atomized liquid precursor chemicals differ from those described in the past in which droplet aerosols are used. In US-A-5278138 to Ott et al . a multicomponent liquid precursor is first atomized to form an aerosol having droplet diameters primarily in the 0.1 to 10 μm in diameter range. The aerosol is then mixed with a suitable oxygen-containing carrier gas and injected into a reactor with a heated zone for vaporization and subsequent chemical vapor deposition to

SBBSI1TUTE produce superconducting thin films, such as yttrium- barium-copper-oxide. Similarly US-A-5271957 to Wernberg et al . describes the formation of LiNb0₃ thin films with special electrooptic, ferroelectric and piezoelectric properties by aerosolizing a liquid precursor chemical and introducing the aerosol into a conventional reactor for vaporization and chemical deposition. In both cases, the reactor used is conventional. The addition of a separate heating zone in the reactor allows the liquid source chemical in aerosol form to be vaporized for subsequent deposition on a substrate in the reactor.

SUMMARY OF THE INVENTION The present invention provides a vaporizer using an aerosol generator that atomizes a liquid into small and larger droplets carried in a gas stream at substantially room temperature. The aerosol in the form of a spray is carried into a heated chamber for vaporization as the gas stream moves across a heated wall of the chamber and is discharged. The aerosol generator breaks the liquid into droplets both large and small, that vaporize. The resultant vapor/gas mixture is introduced into a separate chemical vapor deposition (CVD) chamber. The two chamber approach permits optimizing each chamber for its desired function. The atomization can be accomplished with reagent liquid at or near normal room temperature so that no thermal degradation of the material will take place during the atomization step. The atomized reagent droplets are mixed with a carrier gas flowing into the atomizer to form an aerosol of suspended reagent droplets. This aerosol is then introduced into a vaporizer having a vaporization chamber where the aerosol (including larger droplets) comes in contact with heated wall surfaces. As heat is transferred from

SUBSTITUTESHEET(RULE 2β) the heated surface to the flowing aerosol stream, the gaseous medium around the suspended reagent droplets becomes heated first. The heated gas in turn heats the suspended aerosol droplets to cause them to vaporize. Direct physical contact between the liquid reagent and the heated surfaces in the vaporization chamber can thus be greatly reduced or avoided. This leads to greatly reduced thermal decomposition of liquid reagent which is caused by direct contact between the liquid droplets and the heated surface. Larger droplets are vaporized upon contact with the heated walls, but decomposition is minimized. The vaporizer is capable of provided a stable source of vapor, with precisely controllable operating characteristics for chemical vapor deposition of metal, semiconductor or insulating thin films and related applications.

There is little clogging of the vaporizer due to material decomposition by direct contact with a heated surface. Flash vaporize of the reagent liquid is carried out in a rapid and reproducible manner. The method and apparatus in the preferred form achieves a high vaporization rate, with reduced physical size over existing equipment because the vaporizer can be compact but the interior of the vaporization chamber has a large, effective vaporization surface area. This system also increases the rate of vapor output per unit of carrier gas input, thus increasing the vapor/carrier gas mass ratio. The present invention provides a vaporizer with a rapid time response so that vapor is generated the instant the aerosol is introduced into the heated vaporization chamber. The transfer to the separate CVD chamber can be through an orifice, a capillary tube or other restrictive passageway to obtain turbulent mixing for uniform mixing of the vapor and carrier gas. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic block diagram of a vapor generator made according to the present invention;

Figure 2 is a schematic diagram of a vapor generator such as that shown in Figure 1 used in connection with a chemical vapor deposition chamber for thin film deposition of materials carried in the gas/vapor mixture obtained;

Figure 3 is a schematic diagram of a compressed gas atomizer or aerosol generator for forming a reagent aerosol for the heated vaporization chamber of

Figure 1, with parts in section and parts broken away;

Figure 4 is a schematic diagram^' of an ultrasonic atomizer for forming an aerosol for the heated vaporization chamber of Figure 1;

Figure 5 is a schematic diagram of a compressed gas atomizer combined with a heated vaporization chamber in a single housing for making the design compact and for spraying larger droplets into the vaporization chamber;

Figure 6 is a schematic diagram of the device of Figure 5 showing the use of compressed gas to flush liquids from passageways to avoid drying and plugging; Figure 7 is a schematic diagram of the device of Figure 5 showing the use of a solvent to flush and clean the interior of a vaporization chamber with parts in section and parts broken away; and

Figure 8 is a sectional view of a atomizer nozzle used with the present invention for illustrating dimensional relationships for obtaining the desired size reagent droplets.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 illustrates a vapor generator illustrated generally at 10 which includes a number of components including a carrier gas source 12, and a source of a reagent liquid 14. The carrier gas from source 12 is transferred at high velocity into an aerosol generator or atomizer 16. Reagent liquid from source is introduced into the gas stream or jet in aerosol generator 16. The high velocity gas and reagent liquid provide an output aerosol that moves in a path indicated at 18. The aerosol stream moves into a vaporizer 19 having a heated vaporization chamber 20 that has interior wall surfaces raised to a selected temperature so that it has hot wall surfaces that heat the aerosol stream. The walls are insulated so the exterior remains cool . The gas forming the carrier for the aerosol particles is heated immediately to vaporize droplets in the aerosol. The reagent is vaporized. A gas vapor mixture flows from the vaporizer along a flow path 22.

The aerosol is heated by the hot surfaces of the heated vaporization chamber, which surfaces are heated by heaters represented schematically at 24. Very few aerosol droplets directly contact the interior wall surfaces of vaporization chamber 20, but the droplets are vaporized by heat transfer from the walls to the carrier gas and then to the aerosol particles . The heat transfer through the carrier gas reduces clogging of the vaporizer due to material decomposition. A flash vaporization occurs because of the rapid heating of the carrier gas .

In Figure 2, the gas/vapor mixture moves along the flow path 22 in the manner previously described in connection with Figure 1, and is discharged into a film deposition chamber 26 for chemical vapor deposition

(CVD) , or in other words for depositing a film onto products which are illustrated schematically at 28 supported or suspended within the chamber 26. One key to good chemical vaporization is to have a uniform composition vapor being fed at a uniform rate into the deposition chamber, so that the product will be uniformally coated with the deposited materials. The vaporizer construction thus is of importance to achieve the uniform flow of the vapor, at a relatively high rate for efficiency, while keeping the vaporizer small.

The reagent liquid is formed into an aerosol in the present invention at near normal room temperatures, so that no thermal degradation of the material will take place.

An atomizer or aerosol generator that will provide a uniform discharge of an aerosol is shown schematically in Figure 3. The aerosol generator 16A is shown in somewhat different scale. The compressed gas from source 12 enters a passageway 30 having an orifice or nozzle 32 at the inner end. The orifice or nozzle forms a jet of compressed gas passing through the nozzle 32 and into passageway 33 that aspirates reagent liquid from the source 14 through a passageway 34. The reagent liquid enters the passageway 32 and is broken up into droplets to form the high velocity aerosol stream indicated at 36 that will be expelled along the output path 18.

The pressurized carrier gas flows through the orifice or nozzle 32 to form a high velocity gas jet resulting in the atomization of the liquid reagent and forming the aerosol 36. The reagent liquid from source 14 is introduced into the gas jet in chamber 33 and is atomized to form a droplet aerosol that is at the desired gas/vapor mixture ratio. The aerosol is discharged along the flow path 18, and it is then introduced into the heated vaporization chamber 20. The carrier gas from source 12 and the reagent liquid from source 14, as shown in Figure 4 can be introduced into an ultrasonic aerosol generator or atomizer 38 that uses an ultrasonic transducer 40 mounted to a wall 42 of the aerosol generator or atomizer chamber 39. The ultrasonic generator can extend at least partially into or fully into a pool 43 of the reagent liquid that is introduced into the aerosol generator chamber 39. This ultrasonic transducer 40 provides vibrational energy at a high frequency to break up the reagent liquid into droplets capable of being carried by the carrier gas in a gas stream out through a path 44 as an aerosol . The aerosol is provided to the vaporizer 19. Again, the atomization is done at or near room temperature, so the advantages mentioned for the aerosol generator 16 are available using aerosol generator 38.

In Figure 5, a combined heated vaporization chamber and atomizer is illustrated. In this form of the invention, a housing 48 has an atomizer section 50 that includes a passageway 52 and an orifice or nozzle

54 that receives compressed gas from the source 12. The gas goes through the orifice or nozzle and forms a jet in a passageway 55. The reagent liquid from the source 14 flows through a passageway 56 into the passageway 55 so that the liquid is broken up into droplets by the high velocity jet of gas. The gas jet is discharged as a droplet spray stream indicated at 58. The high velocity droplet spray passes directly through an insulated divider wall 60 in the housing 48. The housing 48 thus defines an interior vaporization chamber

62 that has suitable heaters 64 along its walls. The heaters will heat the walls to a sufficient temperature to cause vaporization of the droplets as the droplet stream passes the walls and with some direct impingement on the walls. The output from the heated vaporization chamber 62 comes out as a gas/vapor mixture through an outlet tube 68 that is a restricted passageway leading to a separate CVD chamber. As shown, the outlet tube 68 includes an orifice 68A between the chamber 62 and the CVD chamber for providing uniform mixing of the gas/vapor mixture by causing turbulence. The outlet tube 68 can include a capillary or other restrictions for promoting the mixing. Thus, passageways 22 and 44 can have orifices or may be otherwise restricted, as desired. The wall 60 has an insulation layer 61 to keep the nozzle 54 at or near room temperature.

Figure 5 shows a compressed gas atomizer spraying liquid reagent droplets directly onto the heated surface in the vaporization chamber opposite from the nozzle. Some of the droplets (usually those larger than about 10 μm in diameter) may hit the heated surface of the opposite wall and be vaporized on contact. Because of the small droplet size produced by the atomizer section 50, vaporization is nearly instantaneous and complete. Smaller droplets, however, do not have enough forward momentum to collide with the heated surface of the opposite wall . They are heated and vaporized by indirect heating through the intervening carrier gas layer. These small droplets do not come into direct physical contact with the heated surface and thermal decomposition does not occur for such small droplets. Overall, thermal decomposition of the reagent liquid is greatly reduced from conventional units used in vaporizing reagents for chemical vapor deposition. Clogging and crust formation in the vaporizer is greatly reduced, or largely eliminated. When vapor generation is stopped by stopping the reagent liquid flow to the vaporizer shown in Figure 5, the solution remaining in the liquid passageway 56 in the atomizer may evaporate to form a residue. To prevent residue formation in the liquid passageway, compressed gas can be introduced into the atomizer as is shown in Figure 6, to blow out the liquid in passageways at the end of a cycle of use. This will insure that the small liquid passageway 56 in the atomizer can be kept clean and free of dried out residue that may cause plugging.

After some period of use, some solid residue may build up on the heated surface in the vaporization chamber. It is desirable to have some means of cleaning such surfaces without removing the unit from the CVD system for maintenance.

In Figure 7, the combined housing 48 having both the aerosol generator section and the heated vaporization chamber section has passageway 56 connected to the valve 70, and a solvent source 78 is connected to the valve 70 in place of compressed gas source 72, to permit introducing solvents into the nozzle 54 and passageways in the aerosol generator. Reagent flow from the source 14 is stopped, when the valve 70 is in its position shown in Figure 7, and the solvent is sprayed under pressure into the heated vaporizer to wash out the build up of residue in the passageways and also in the vaporizer. In other words the solvent will go into the passageway 55 and will be carried in a gas jet 80 into the interior of the chamber section forming the vaporizer to rinse down and clean the wall surfaces. A drain shown at 82 is provided in the housing 48 for draining out the solvent and any residue that the solvent carries with it. Other atomizers, preferably operating at or near room temperature, to form an aerosol or droplet spray also can be used. The combination of other atomizers providing an aerosol or droplet spray that is introduced into a heated vaporization chamber to produce a hot gas/vapor mixture can be achieved by those skilled in the art. Therefore, such combinations are not specifically described.

In designing compressed gas atomizers for vaporization, it has been found that certain dimensions preferably are maintained to insure proper functioning of the atomizer.

Referring to Figure 8, the dimensions Dl, D2 and D3 are shown. Dl, the diameter of the orifice or nozzle through which the compressed gas flows, is determined by the desired gas flow rate and the compressed gas pressure. D2 , the diameter of the liquid flow passageway, is determined by the liquid feed rate and the vapor output rate required. Too small a D2 will result in insufficient liquid flow to the atomizer, and too large a D2 will cause pulsation in the output vapor flow rate. The preferred ratio of D2 to Dl is between 1 and 5. Similarly, D3 , the distance between the liquid reagent passageway and the compressed gas orifice used to provide a high velocity jet of gas, should also be maintained between reasonable limits. A small D3 will generally result in small droplet sizes, which are desired for rapid vaporization. But too small a D3 will lead to incomplete atomization of the liquid. However, too large a D3 will result in large atomized droplets, which are undesirable because of the long vaporization time needed for large drops. For desired functioning of the atomizer, the ratio of D3 to Dl is preferably between 1 and 20. As distinguished from the prior art, in the present invention, the liquid source chemical is atomized to form an aerosol, which is then vaporized in one chamber to produce a vapor/gas mixture. This mixture is then introduced into a separate chamber to carry out chemical vapor deposition (CVD) , plasma- enhanced chemical vapor deposition (PECVD) , and other film formation steps. This two chamber approach allows for the first chamber to be optimized for vapor generation and the second chamber optimized for chemical vapor deposition. Using two separate chambers, the aerosol generator such as and the vaporization chamber such as 50, 62 can operate at one pressure (for instance, atmospheric pressure at 760 Torr) and the CVD chamber 26 at a lower pressure (for instance, a vacuum pressure of 1 Torr) . The vapor and carrier gas can be uniformly mixed by turbulent mixing hen the mixture is introduced into the CVD chamber through an orifice such as 68A in Figures 5-7, a capillary tube, or other forms of restrictive passageways as the restrictions permit the pressure differential. Uniform mixing of vapor and the carrier gas before introduction into the CVD chamber is important since it allows for the formation of uniform thin films of high quality. This would be impossible with the apparatus of US-A-527138 and 5271957.

The use of an aerosol having small diameter droplets in the 0.1 to 10.0 microns is shown in the prior art. The small droplet diameter limits the liquid to carrier gas ratio that can be achieved. In conventional CVD reactor using gaseous precursors, the mass ratio of the reactant gas (such as silane) to carrier gas (such as nitrogen) is typically a few percent in order to carry out chemical vapor deposition

soBsrmire SHEET _(Rϋ at an acceptable rate for commercial integrated circuit device fabrication. In the case of droplet aerosol that can be produced by conventional atomizers and nebulizers, the precursor droplet mass concentration in the aerosol is typically 1 gram per cubic meter of carrier gas, or a reactant to carrier gas ratio on the order of 0.1%. Such a low reactant to carrier gas ratio, while adequate for making laboratory samples for evaluation, would be inadequate for commercial production purposes.

In the present invention as shown in Figures 5-7, an atomizer is used as a sprayer to spray the liquid precursor directly into a heated vaporization chamber. Droplets considerably larger than 10 μm (for instance, 100 μm, or even 1000 μm) in diameter can be sprayed into the chamber for vaporization. This greatly increases the reagent to carrier gas ratio then can be achieved, making it practical to use liquid source chemicals for commercial production purposes. While large droplets may impact on the heated surface and under go some thermal decomposition, the decomposition product will usually remain in the vaporizer and not be carried by the gas flow to cause contamination of the product substrates, which is located in the separate CVD chamber. This effectively isolates the contamination generation process from the film deposition process to enhance the product yield. Using a single reactor for both vaporization and film deposition such as those described by the prior art, the decomposition products generated in the heated zone can easily be re-entrained by the gas flow to contaminate the product substrates located down-stream in the same reactor.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A device to produce a source of a gas stream carrying a vapor of a selected reagent therein comprising an aerosol generator for generating an aerosol in a gas stream, the aerosol being made up of droplets containing the selected reagent, a separate vaporization chamber having heated surfaces over which the gas stream passes, the heated surfaces being heated to a temperature to cause vaporization of the droplets carried in the gas stream whereby the gas stream exits the vaporization chamber carrying vapor formed from the droplets, and a separate chemical vapor deposition (CVD) chamber for receiving the gas stream from the vaporization chamber.

2. The device of claim 1, wherein said aerosol generator has a nozzle, a compressed gas source connected to discharge through the nozzle, to form the gas stream, a passageway open to the nozzle for a liquid containing the reagent to flow into the passageway to form small droplets of the liquid reagent in the gas stream.

3. The device of claim 1, wherein said aerosol generator is at substantial ambient room temperature.

4. The device of claim 1, wherein said aerosol generator and said vaporization chamber are mounted in a single housing such that droplets are sprayed directly into the vaporization chamber, and an insulated wall between the vaporization chamber and the aerosol generator for reducing heat transfer to the aerosol generator.

5. The device of claim 1, wherein said aerosol generator comprises a nozzle for receiving a compressed gas, and forming a gas jet on an outlet side of said nozzle, an atomization region open to the liquid containing the reagent, for the liquid to flow into said region and forming an aerosol in combination with the gas jet, which comprises the gas stream.

6. The device of claim 5 and a valve connected for controlling flow of the liquid reagent into the atomization region of the aerosol generator, said valve being connectable to the liquid reagent and selectively to a source of compressed gas.

7. The device of claim 6 , wherein said aerosol generator has a passageway for carrying a liquid containing the reagent, said passageway having an inlet end, a valve connected to said inlet end, and said valve being selectively coupleable to the source of liquid reagent and to a source of solvent .

8. The device of claim 3 and a restriction that causes turbulent mixing between the outlet and the CVD chamber .

9. A method of forming a vapor and gas mixture for chemical vapor deposition having a vapor of a known reagent therein comprising the steps of forming an aerosol of a liquid containing the reagent, introducing the aerosol into a heated enclosure to vaporize the liquid reagent, causing the gas and vapor formed out from the vaporization chamber, and into a separate chamber for chemical vapor deposition.

SUBSTITUTE SHEET (RIRE 26)

10. The method of claim 9 including the steps of heating a surface of the vaporization chamber to a desired temperature, and passing the aerosol across the surface such that the gas transfers heat to vaporize droplets in said aerosol to form the vapor.

11. The method of claim 9 including the step of passing the gas and vapor formed in the vaporization chamber through a restriction causing turbulent mixing before the gas and vapor formed is introduced into the CVD chamber.

12. The method of claim 11 including the step of maintaining the vaporization chamber and the CVD chamber at different pressures.

13. The method of claim 11 including the step of maintaining the vaporization chamber and the CVD chamber at different temperatures.

14. The method of claim 10 including the step of forming the aerosol by utilizing an ultrasonic aerosol generator, using an ultrasonic transducer to create droplets, and a gas stream to carry the droplets, and passing the aerosol formed into the vaporization chamber .

15. The method of claim 9 including the step of spraying an aerosol containing droplets larger than 10 microns directly into the vaporization chamber to form the gas mixture .