WO2000065127A1

WO2000065127A1 - Apparatus and method for delivery of vapor to a cvd chamber

Info

Publication number: WO2000065127A1
Application number: PCT/US2000/011201
Authority: WO
Inventors: John J. Hautala; Johannes F. M. Westendorp; Louise S. Barriss; Robert W. Milgate
Original assignee: Tokyo Electron Limited; Tokyo Electron Arizona, Inc.
Priority date: 1999-04-27
Filing date: 2000-04-26
Publication date: 2000-11-02

Abstract

CVD reactor (11) is provided with precursor delivery system (12) having evaporation vessel (31) in which high molecular weight solid precursor is converted to vapor by heating it to vapor pressure of at least about 3 Torr. Vessel (31) is connected to CVD reactor chamber (11) through tube (50) of relatively large diameter having small diameter orifice (52). Controller (60) monitors pressure upstream and downstream of orifice (52) and controls flow control device in tube upstream of orifice (52) to produce desired flow rate of precursor vapor into CVD reactor (11). Flow rate is controlled in accordance with standard flow algorithm modified by factors retrieved from look-up flow calibration table in response to measurements of pressures across tube (50).

Description

APPARATUS AND METHOD FOR DELIVERY OF VAPOR TO A CVD CHAMBER

This application is related to the following commonly assigned and copending U.S. patent applications, filed by inventors hereof on even date herewith, which are hereby expressly incorporated by reference herein, entitled: PECVD of Ta Films from Tantalum Halide Precursors; PECVD of TaN Films from Tantalum Halide Precursors;

Thermal CVD of Tan Films from Tantalum Halide Precursors; Plasma Treated Thermal CVD of Tan Films from Tantalum Halide Precursors;

CVD TiN Plug Formation from Titanium Halide Precursors; CVD of Integrated Ta and TaN_x Films from Tantalum Halide

Precursors; and

CVD TaN_x Plug Formation from Tantalum Halide Precursors. Field of Invention

This invention relates to chemical vapor deposition (CVD) and particularly to the delivery to a CVD chamber of vapor from sources that are normally solid at standard temperatures and pressures. Particularly, the invention relates to the delivery of vapors of substances such as CVD precursors to CVD chambers 00/65127

- 2 - for the formation of films, and more particularly, of barrier layer films of, for example, tantalum or tantalum compounds or of titanium or titanium compounds. Background of the Invention

Chemical vapor deposition (CVD) processes such as tnose used in the manufacture of semiconductor devices require delivery of quantities of vapor to a CVD reactor at precisely controlled rates. The quality of the deposited films as well as the efficiency of the deposition process depends in part on the level of precision with which delivery of precursor vapor can be controlled. Film purity, film uniformity, film resistivity and fiim deposition rate are affected by the rates at which gases carrying the materials to be deposited, or which are to react with those gases, are delivered into the deposition chamber.

Materials, particularly metals such as titanium and tantalum, are deposited to form films of the metal, or of compounds of the metal such as titanium nitride ortantaium nitride, by reacting gases such as hydrogen, nitrogen, ammonia or combinations thereof with halides of tantalum or titanium that are delivered to a reaction chamber in vapor form. The metal halide vapor is often produced in an evaporation vessel from which it is usually delivered to the CVD reaction chamber mixed with an inert carrier gas such as helium or argon. The metal halide is typically in a solid state when at room temperature and is vaporized from a liquid or solid state in an evaporation vessel that has been evacuated to a vacuum pressure level. Carrier gas flows through the evaporation vessel and where it is combined with the precursor vapor at a pressure greater than that of the CVD reaction chamber to which the precursor is to be delivered. The carrier gas picks up the evaporated precursor by mixing 0/65127

- 3 - with it so that the mixture can be delivered through passages into the CVD reaction chamber.

The use of a carrier gas presents the disadvantage that the concentration of the precursor gas in the carrier is not precisely known. As a result, accurate metering of a mixture of a carrier gas and a precursor vapor to the CVD reaction chamber does not insure delivery of accurate flow rates of the precursor vapor alone to the reactor. This lack of accuracy in the delivery of the precursor can cause the reactants in the CVD chamber to be either too rich or too lean. This is especially a problem with precursors of high molecular weights of greater than 300 atomic mass units (AMUs), particularly molecular weights in the 500-600

AMU range such as TiX_x, where the precursor molecular weight is substantially greater than that of the low molecular weight carrier, such as argon or helium.

The use of a carrier gas also has the tendency to pick up solid particulates of the precursor in the evaporation vessel and delivering them to the CVD reaction chamber where they present the same disadvantages as other particulate contaminants. Particulates on the surface of a semiconductor wafer during processing can result in the production of defective semiconductor devices. Such particulates are often generated when the precursor is in a solid powder state in the evaporation vessel. With a solid precursor powder, for example, carrier gas can entrain small particles of the precursor powder and transfer them to the processing chamber. A precursor gas can also burrow into the surface of a solid precursor, changing its effective surface area and affecting its evaporation rate over time, which impairs the accuracy of precursor flow rate delivery to the processing chamber. The use of a solid precursor source presents a surface area that is susceptible to change during the evaporation process. As solid material turns to vapor, different rates of evaporation can occur at different portions of the solid material surface. This causes the rate of precursor production to change, which can cause precursor concentration in the carrier gas and the rate of flow of precursor vapor to the reactor to vary.

For the reasons stated above and other reasons, there is a need for a better apparatus and method for delivery of reaction precursor vapor from solid sources to a CVD chamber. Summary of the Invention

An objective of the present invention is to deliver precursor vapor from a source that is in a solid state at standard temperature and pressure to a reaction chamber for use in a chemical vapor deposition (CVD) reaction, and particularly to deliver precursor vapor to a CVD reactor at a precisely controlled rate. A further objective of the present invention is to deliver precursor vapor to a CVD chamber while minimizing the introduction of particulate contamination into the chamber in the process.

In accordance with the principles of the present invention, an evaporation vessel is provided for supplying precursor vapor to a CVD reactor. Solid precursor material is placed in the vessel where it is converted to vapor. In the preferred embodiments of the invention, the evaporation vessel is connected to the CVD reactor chamber through a tube of relatively large diameter in which is placed a small diameter orifice. The solid precursor is heated in the evaporation vessel to a temperature sufficient to produce a precursor vapor pressure that will 00/651

- 5 - cause a flow of the precursor vapor through the tube and orifice and into the CVD reaction chamber at an acceptable flow rate. A controller monitors the pressure upstream and downstream of the orifice and controls a flow control device in the tube upstream of the orifice to produce a desired flow rate of precursor vapor through the tube and into the processing chamber of the CVD reactor.

Preferably, the flow rate is controlled in accordance with factors retrieved from a look-up table in response to the measurements of the pressures. The data in the look-up tables accounts for the flow characteristics of the tube and the orifice, and determines a flow control output signal to which the flow control responds in a way that takes into account both choked and unchoked flow characteristics of the tube and orifice.

In the preferred embodiment of the invention, the evaporation vessel is evacuated and then filled with the precursor vapor without the introduction of carrier gas so that the precursor is the only material occupying the vessel. In this way, the total rate of flow through the tube and the orifice is the rate of flow of only precursor vapor, so that the determination of the rate of flow of the precursor does not require a determination or estimate of the concentration of precursor vapor in the carrier gas, which is often difficult to accurately obtain. In certain preferred embodiments of the invention, the normally solid precursor is heated to a liquid state in the evaporation vessel. Preferably, the inside of the evaporation vessel has vertical walls so that a constant surface area of the liquid precursor source is provided and maintained as the level of liquid precursor in the evaporation vessel changes, which constant surface area in turn 00/651

- 6 - helps maintain a uniform evaporation rate as the precursor source is consumed. The temperatures of surfaces downstream of the precursor source are preferably controlled at temperatures that are higher than the temperature to which the solid source is heated, thereby preventing condensation of the precursor vapor. Such controlled temperatures are all below the reaction temperature of the CVD reaction that is to take place in the CVD processing chamber so that disassociation or other reaction of the precursor does not occur prematurely, but rather only at the surface of the substrate on which the film is to be deposited in the processing chamber. In accordance with a preferred embodiment of the invention, a halide form of a precursor is heated in the evaporation vessel in the absence of carrier gas to produce a vapor pressure in the range of at least about 3 Torr, preferably about 5 to 6 Torr, with pressure in the CVD reactor being preferably in the range of about 0.1 Torr to about 2 Torr, thereby producing a total pressure drop from the evaporation vessel to the CVD reaction chamber of at least about 4 Torr across the tube connecting the evaporation vessel with the CVD reaction chamber, including the flow control devices and orifice connected in the tube. This allows a flow control device in the form of a control valve to be located between the evaporation vessel and the orifice in the tube to produce a pressure drop from the control valve to the CVD reaction chamber that is at least 10 milli- Torr, which can be varied to proportionally control the flow rate.

Precursors such as tantalum pentafiuoride, tantalum pentachloride, tantalum pentabromide and titanium tetraiodide are particularly suitable for use with the present invention. The precursors are heated in the evaporation „„_.««-,, 00/65127

- 7 - chamber to the temperature that produces a desired vapor pressure in the evaporation chamber. If melting of the precursor from a solid to a liquid produces an acceptable vapor pressure, heating the precursor to a liquid state is preferred. If alternative halide forms of a desired metal precursor are available and are regarded as in all other respects equal, the one that produces the desired vapor pressure while in a liquid state is preferred.

The present invention preferably employs a process controller that contains a multiplier table with values that control a flow control valve at the upstream end of the line from the evaporation chamber to the CVD chamber. Different sets of values are provided for choked and uπchoked flow. Choked flow occurs when the flow through the orifice in the tube reaches a point where it is no longer dependent on the pressure downstream, but only the pressure upstream of the orifice. Unchoked flow is dependent on the ratio of the outlet pressure to the inlet pressure. The controller determines the characteristics of the flow and provides the appropriate multiplier for the control signal to the control valve at the inlet side of the tube.

These and other objectives of the present invention will be readily apparent from the following detailed description of the present invention in which: Brief Description of the Drawings The figure is a schematic diagram of one preferred embodiment of a CVD system embodying principles of the present invention. Detailed Description of the Preferred Embodiments

The figure diagrammaticaily illustrates a chemical vapor deposition (CVD) system 10 that includes a CVD reactor 11 and a precursor delivery system 12, 0/65127

- 8 - connected to the reactor 11 and which includes the system components

responsible for the delivery of precursor vapor to the reactor 11. In the reactor 11 , a reaction is carried out to convert a precursor vapor of, for example, tantalum chloride or other tantalum halide compound, into a film such as, for example, a barrier layer film of tantalum or tantalum nitride.

The precursor delivery system 12 is made up of a source 13 of precursor vapor and a metering system 15. The source 13 has an outlet 14, which connects to the metering system 15, which in turn is connected to a reactant gas inlet 16 of the CVD reactor 11. The source 13 is configured to supply a precursor vapor, for example a tantalum halide vapor, from a solid or liquid tantalum halide compound, at a rate that is sufficient to support the CVD reaction in the chamber 11. The compound is one that is in a solid state when at standard temperature and pressure. The precursor in the source is maintained at a controlled temperature that will produce a desired vapor pressure of the precursor at the outlet 14 of the source 13 where it connects to the metering system 15. Preferably, the vapor pressure of the precursor itself is sufficient to allow the metering system 15 to deliver the precursor vapor to the reactor 11 at a desired flow rate without the use of a carrier gas. The metering system 15 maintains a flow of the precursor vapor from the source 13 into the reactor 11 at a rate that is sufficient to maintain a commercially viable CVD process in the reactor 11.

The reactor 11 is a generally conventional CVD reactor and includes a vacuum chamber 20 that is bounded by a vacuum tight chamber wall 21. In the chamber 20 is situated a substrate support or susceptor 22 on which a substrate 0/65127

- 9 - such as a semiconductor wafer 23 is supported. The chamber 20 is maintained

at a vacuum appropriate for the performance of a CVD reaction that will deposit a film such as a tantalum or tantalum nitride barrier layer on the semiconductor wafer substrate 23. A preferred pressure range for the CVD reactor 11 is in the range of from 0.2 to 5.0 Torr, preferably in the range of from 1 to 2 Torr. The vacuum is maintained by controlled operation of a vacuum pump 24 and of inlet gas sources 25 that may include, for example, an inert gas source 27 for a gas such as argon (Ar) or helium (He) and one or more reducing gas sources 26 of, for example, hydrogen (H₂), nitrogen (N₂), or ammonia (NH₃), for use in carrying out a metal halide reduction reaction, such as a reaction to deposit Ta or TaN or TiN, for example. The gases from the sources 25 enter the chamber 20 through a showerhead 28 that is situated at one end of the chamber 20 opposite the substrate 23, generally parallel to and facing the substrate 23.

The precursor gas source 13 includes a sealed evaporator 30 having therein an evaporation vessel 31 , which is preferably in the shape of a cylinder having a vertically oriented axis of symmetry 32. The vessel 31 has a cylindrical inner wall 33 formed of a high temperature tolerant and non-corrosive material such as the alloy INCONEL 600. The inside surface 34 of the wall 33 is highly polished and smooth. The wall 33 has a flat circular closed bottom 35 and an open top, which is sealed by a cover 36 of the same heat tolerant and non- corrosive material as the wall 33. The outlet 14 of the source 13 is situated in the cover 36. The cover 36 is sealed to a flange ring 37 that is integral to the top of the wall 33 by a vacuum tight seal 38. When high temperatures are used, such as those needed for Til₄ pr TiBr₄, the seal 38 is preferably a high - 10 - temperature tolerant vacuum compatible seal material such as HELICOFLEX, which is formed of a C-shaped nickel tube surrounding an INCONEL coil spring. With materials requiring lower temperatures, such as TaCI₅ and TaF₅, a conventional elastomeric O-ring may be used to seel the cover 36 to the flange ring 37.

Connected to the vessel 31 through the cover 36 is a source 39 of a carrier gas or purge gas, which is preferably an inert gas such as helium or argon. The source 13 includes a mass of precursor material such as tantalum fluoride, tantalum chloride or tantalum bromide (TaX) contained in and situated at the bottom of the vessel 31 , which is loaded into the vessel 31 at standard temperature and pressure in a solid state. The vessel 31 is filled with tantalum halide vapor by placing the solid mass of TaX in the vessel 31 and sealing the cover 36 to the top of the vessel wall 33, then heating the wall 33 of the vessel 31 to raise the temperature of the TaX compound sufficiently high to achieve a desired TaX vapor pressure in vessel 3 .

The precursor halide is supplied as a precursor mass 40 that is placed at the bottom of the vessel 31 , where it is heated, preferably to a liquid state as long as the resulting vapor pressure is in an acceptable range. Purge gas and TaX vapors are, however, first evacuated from the vessel 31 with a vacuum pump 41 , which is connected through the cover 36, so that only TaX vapor from the TaX mass 40 remains in the vessel 31. Where the mass 40 is liquid, the vapor lies above the level of the liquid mass 40. Because wall 33 is a vertical cylinder, the surface area of TaX mass 40, if a liquid, remains constant regardless of the extent of depletion of the TaX. - 11 - The delivery system 12 is not limited to direct delivery of a precursor 40 but can be used in the alternative for delivery of precursor 40 along with a carrier gas, which can be introduced into the vessel 31 from gas source 39. Such a gas may be hydrogen (H₂) or an inert gas such as helium (He) or argon (Ar). Where a carrier gas is used, it may be introduced into the vessel 31 so as to distribute across the top surface of the precursor mass 40 or may be introduced into the vessel 31 so as to percolate through the mass 40 from the bottom 35 of the vessel 31 with upward diffusion in order to achieve maximum surface area exposure of the mass 40 to the carrier gas. Yet another alternative is to vaporize a liquid that is in the vessel 31. However, such alternatives add undesired particulates and do not provide the controlled delivery rate achieved by the direct delivery of the precursor, that is, delivery without the use of a carrier gas. Therefore, direct delivery of the precursor is preferred.

Where it is desirable to introduce the precursor into the reaction chamber 11 through the showerhead 28 along with a carrier gas, it is preferred that the carrier gas be introduced into tube 50 near its outlet end, from a source 87 connected downstream of the downstream pressure sensor 57 of the metering system 15 so that it does not interfere with the accurate flow rate delivery of direct precursor delivery that is preferred with the system 10. To maintain the temperature of the precursor 40 in the vessel 31 , the bottom 35 of the wall 33 is in thermal communication with a heater 44, which maintains the precursor 40 at a controlled temperature, preferably above its melting point, at such a temperature that will produce a vapor pressure in the approximate range of at least about 3 Torr. preferably in the range of from about - 12 -

4 to about 10 Torr, when pure precursor vapor is used, and at a lower vapor

pressure of about 1 Torr when a carrier gas is used. The exact vapor pressure depends upon other variables such as the quantity of carrier gas, the effective surface area of the mass 40 and other variables. In a direct tantalum delivery system 10, that is, in a system for delivery of tantalum precursors without a carrier gas, a preferred vapor pressure can be maintained of at least 5 Torr by heating the a tantalum halide precursor in the 95°C to 205°C range, depending on the tantalum halide compound being used. For tantalum pentahalides the desired temperatures are as follows: at least about 95°C for TaF₅; at least about 145°C for TaCI₅; and at least about 205°C for TaBr₅. The melting points of the respective fluoride, chloride and bromide of tantalum are in the 97°C to 265°C range. A much higher temperature is required for tantalum pentaiodide (Tal_s) to produce a sufficient vapor pressure in the vessel 31. In any event, temperatures should not be so high as to cause premature reaction of the precursor vapor with reducing gases in a mixing chamber within the showerhead 28 or elsewhere before contacting the wafer 23.

For purposes of example, a temperature of 180°C is assumed to be the control temperature for the heating of the bottom 35 of the vessel 31. This temperature is appropriate for producing a desired vapor pressure with a titanium tetraiodide (Til₄) precursor. Given this temperature at the bottom 35 of the vessel 31 , to prevent condensation of the precursor vapor on the walls 33 and on the cover 36 of the vessel 31 , the cover 36 is maintained at a higher temperature than the heater 44 at the bottom 35 of the wall 33 of, for example, 190°C, by a separately controlled a heater 45 that is in thermal contact with the 0/65127

- 13 - outside of the cover 36. The temperature in the vessel 31 should be kept below the temperature at which TaX gas disassociates to form Ta⁺ and X^" atoms.

The sides of the vessel wall 33 are surrounded by an annular trapped air space 46, which is contained between the vessel wall 33 and a surrounding concentric outer aluminum wall or can 47. The can 47 is further surrounded by an annular layer of silicone foam insulation 48. This temperature maintaining arrangement keeps the vapor in a volume of the vessel bounded by the cover 36, the sides of the walls 33 and the surface 42 of the precursor mass 40 in temperature range of between 180°C and 190°C and at a pressure of at least about 3 Torr, preferably at least about 5 Torr. The temperature that is appropriate to maintain the desired pressure will vary with the precursor material, which is primarily contemplated as a being tantalum halide or titanium halide compound. Vapors from other precursors that are solid at room temperature but have low vapor pressures can be similarly delivered. The vapor flow metering system 15 includes a delivery tube 50 of at least

1/2 inch in diameter, or at least 10 millimeters inside diameter, and preferably larger so as to provide no appreciable pressure drop at the flow rate desired, which is at least approximately 2 to 40 standard cubic centimeters per minute (SCCM). The tube 50 extends from the precursor gas source 13, to which it connects at its upstream end to the outlet 14, to the reactor 11 to which it connects at its downstream end to the inlet 16. The entire length of the tube from the evaporator outlet 14 to the reactor inlet 16 and the showerhead 28 of the reactor chamber 20 is also preferably heated to above the evaporation 00/65127

- 14 - temperature of the precursor gas, for example, to 195°C. The precursor is

preferably at its coldest point in the system 10 at the precursor mass 40.

/^• In the tube 50 is provided a baffle plate 51 in which is centered a circular orifice 52, which preferably has a diameter of approximately 0.089 inches. With a typical pressure drop from the precursor gas source outlet 14 to the reactor inlet 16, which may be of approximately 5 Torr, for example, a viscous or laminar flow, and not a turbulent flow, is maintained in the tube 50. A variable orifice control valve 53 is provided in the tube 50 between the baffle 51 and the precursor gas source outlet 14 to control the pressure in the tube 50 upstream of the baffle 51 and thereby control the flow rate of precursor gas through the orifice 52 and the tube 50 to the inlet 16 of the reactor 11. A shut-off valve 54 is provided in the line 50 between the outlet 14 of the evaporator 13 and the control valve 53 to close the vessel 31 of the evaporator 13.

Pressure sensors 55-58 are provided in the system 10 to provide information to a controller 60 for use in controlling the system 10, including controlling the flow rate of precursor gas from the delivery system 15 into the chamber 20 of the CVD reactor 11. The pressure sensors include sensor 55 connected to the tube 50 between the outlet 14 of the evaporator 13 and the shut-off valve 54 to monitor the pressure in the evaporation chamber 31. A pressure sensor 56 is connected to the tube 50 between the control valve 53 and the baffle 51 to monitor the pressure upstream of the orifice 52, while a pressure sensor 57 is connected to the tube 50 between the baffle 51 and the reactor inlet 16 to monitor the pressure downstream of the orifice 52. A further pressure sensor 58 is connected to the chamber 20 of the reactor 11 to monitor the - 15 - pressure in the CVD chamber 20. The control valve 53 is operative to affect a pressure drop from the control valve 53, through the orifice 52 and into the reaction chamber 11 that can be varied above about 10 milliTorr and to produce a flow rate of precursor into the chamber 11 that is proportional to this controlled pressure drop.

Control of the flow of precursor vapor into the CVD chamber 20 of the reactor 11 is achieved by the controller 60 in response to the pressures sensed by the sensors 55-58, particularly the sensors 56 and 57 which determine the pressure drop across the orifice 52. When the conditions are such that the flow of precursor vapor through the orifice 52 is unchoked flow, the actual flow of precursor vapor through the tube 52 is a function of the pressures monitored by pressure sensors 56 and 57, and can be determined from the ratio of a) the pressure measured by sensor 56, on the upstream side of the orifice 52, to b) the pressure measured by sensor 57, on the downstream side of the orifice 52. When the conditions are such that the flow of precursor vapor through the orifice 52 is choked flow, the actual flow of precursor vapor through the tube 52 is a function of only the pressure monitored by upstream pressure sensor 57. In either case, the existence of choked or unchoked flow can be determined by the controller 60 by interpreting the process conditions. When the choked/unchoked determination is made by the controller 60, the flow rate of precursor gas can then be determined by the controller 60 through calculation.

Preferably, accurate determination of the actual flow rate of precursor gas is calculated by retrieving flow rate data from lookup or multiplier tables stored in a non-volatile memory 61 accessible by the controller 60. When the actual flow rate of the precursor vapor is determined, the desired flow rate can be maintained by a closed loop feedback control of one or more of the variable orifice control valve 53, the CVD chamber pressure through evacuation pump 24 or control of reducing or inert gases from sources 26 and 27, or by control of the temperature and vapor pressure of the precursor gas in chamber 31 by control of heaters 44 and 45.

Determination of whether the flow through the orifice 52 is choked or unchoked flow and the calculations of flow rate as a function of differential pressure and passage geometry is known in the art, and is explained in A Users Guide to Vacuum Technology, Second Edition, by John F. O'Hanlon, John Wiley & Sons, New York, particularly at pages 29-30 thereof. Such textbook calculations provide an estimate of the flow of high molecular weight precursors such as TiX_x and TaX_x. The controller 60 performs this calculation of theoretical flow rate in response to the pressure and temperature measurements from the sensors. These theoretical flow rate calculations are adjusted by the controller 60 with data from the lookup tables stored in the memory 61.

The lookup tables in the memory 61 are set up by a calibration process in which a test cylinder or container of a known volume comparable to that of the reaction chamber 11 is connected downstream of the metering system 15 and set to the approximate pressure and temperature parameter ranges of that will be used during processing in the reaction chamber 11. Then, the delivery system 12 is operated to cause flow of the precursor gas into the test cylinder under the same parameters to be used for actual CVD processing. The pressure rise in the test cylinder is measured at various time intervals and the 00/651

- 17 - actual flow rates of precursor gas into the test cylinder are calculated as a function of pressure settings. These calculations are then compared to the flow rate calculations made by the controller using the theoretical equations from the literature. The actual and theoretical flow rates are compared and entries are made into the lookup tables in the memory 61 that will enable the controller 60 to adjust the theoretical calculations to equal the actual flow rate data from the calibration tests. Each system 10 should be separately calibrated in this way. During CVD processing, the calculation and control of precursor flow rate utilizing a flow formula adjusts the flow for different precursor materials, different downstream processing pressures and other parameters, while the use of the table of flow correction multipliers from memory 61 compensates for hardware variations as pressure and the other variable parameters change.

Processes by which the present invention may be used for deposition of tantalum or tantalum compounds or for titanium and titanium nitride compounds are disclosed in the commonly assigned and copending patent applications, filed on even date herewith and incorporated by reference herein, as set forth above.

From the above description of the invention and the preferred embodiments, one skilled in the art will appreciate that variations and additions may be made to the processes and the equipment described without departing from the principles of the invention.

What is claimed is:

Claims

1. A method of delivering halide precursor vapor of a metal coating

material from a solid source thereof to a CVD chamber, the method comprising: enclosing in an evacuated evaporation vessel a high molecular weight metal halide precursor that is a solid at standard temperature and pressure; controlling the temperature of the precursor in the evaporation vessel so as to produce a precursor vapor in the evaporation vessel at a vapor pressure of at least approximately 3 Torr; communicating the precursor vapor through a passage from the evaporation vessel to a CVD chamber, in which chamber a substrate is supported for coating with film of the metal or of a compound of the metal by a

CVD reaction of the precursor, and through a flow restriction orifice in the passage; and controlling the pressure of the precursor vapor across the passage in accordance with stored flow characteristic data to maintain a flow of vapor of the precursor from the evaporation vessel to the CVD chamber through the orifice and passage to deliver precursor vapor to the CVD chamber at a flow rate that will provide for the deposition of the film at a predetermined production rate.

00/65127

- 19 -

2. The method of claim 1 wherein:

the providing of the passage includes providing the passage with a width sufficient for the passage to have an effect on the flow of vapor therethrough that is immaterial relative to the effect on the flow of the orifice.

3. The method of claim 1 wherein:

the controlling of the temperature includes controlling the temperature of the precursor so as to maintain the precursor in a liquid state throughout a substantial portion of its vertical height.

4. The method of claim 3 wherein: the evacuation vessel has at least a portion thereof having a generally uniform horizontal cross sectional area.

5. The method of claim 1 wherein:

the controlling of the pressure includes controlling the ratio of the pressure downstream of the orifice to the pressure upstream of the orifice so as to deliver precursor vapor to the CVD chamber by unchoked flow through the passage at a flow rate that will provide for the deposition of the film at a predetermined production rate.

6. The method of claim 1 wherein:

the controlling of the pressure includes controlling the pressure upstream of the orifice so as to deliver precursor vapor to the CVD chamber by choked flow through the passage at a flow rate that will provide for the deposition of the film at a predetermined production rate.

7. The method of claim 1 further comprising:

automatically monitoring process parameters to determine whether unchoked or choked flow is produced through the passage, and, in response to a determination thereof, controlling pressure by a process selected from the group consisting of: controlling the ratio of the pressure downstream of the orifice to the pressure upstream of the orifice so as to deliver precursor vapor to the

CVD chamber by unchoked flow through the passage at a flow rate that will provide for the deposition of the film at a predetermined production rate; and controlling the pressure upstream of the orifice so as to deliver precursor vapor to the CVD chamber by choked flow through the passage at a flow rate that will provide for the deposition of the film at a predetermined production rate. 00/65127

- 21 -

8. The method of any of claims 1 through 7 wherein: the enclosing of the metal halide precursor and controlling of the precursor temperature are performed without a carrier gas in the evaporation vessel.

00/65127

- 22 -

9. An apparatus for delivering halide precursor vapor of a metal coating material from a solid source thereof to a CVD chamber comprising: a sealable evaporation vessel having a vacuum pump connected thereto for evacuating the vessel;

the evaporation vessel having a heater controllable to heat high molecular weight metal halide precursor in the vessel to a vapor pressure of at least about 3 Torr in the vessel when the vessel has been evacuated; a gas conducting passage extending from the evaporation vessel and having an outlet connectable to a CVD reaction chamber in which a substrate is to be supported for coating with film of the metal or compound of the metal by a CVD reaction of the precursor, the passage having a flow restriction orifice therein, the passage being of sufficiently wide diameter to so as to insignificantly affect the pressure drop across the tube of vapor flowing through the orifice; and a flow control device connected to the passage upstream of the orifice and having a programmed controller connected thereto, the controller being programmed to control the flow of the precursor vapor from the outlet of the passage accordance with stored flow characteristic data to maintain a flow of vapor of the precursor from the evaporation vessel to the CVD chamber via the orifice and passage to deliver precursor vapor to the CVD chamber at a flow rate that will provide for the deposition of the film at a predetermined production rate. _ΛΛ ._«„_ 00/65127

- 23 -

10. The apparatus of claim 9 wherein:

the heater is controllable to heat a metal halide precursor having a molecular weight of at least 300 atomic mass units to a vapor pressure of at least about 3 Torr.

11. The apparatus of claim 10 wherein:

the heater is controllable to heat a tantalum halide precursor to a vapor pressure of at least about 3 Torr.

12. The apparatus of claim 10 wherein: the heater is controllable to heat a titanium halide precursor to a vapor pressure of at least about 3 Torr.

13. The apparatus of claim 9 wherein: the programmed controller is programmed to control the flow of the precursor vapor from the outlet of the passage accordance in a predetermined relationship to the upstream and downstream pressures across the passage over a predetermined production rate flow range and modifying the relationship in accordance with tabulated data stored in response to calibration of the flow characteristics of the passage.

14. A CVD processing apparatus comprising:

a sealable evaporation vessel having a vacuum pump connected thereto for evacuating the vessel; the evaporation vessel having a heater controllable to heat high molecular weight metal halide precursor in the vessel to a vapor pressure of at least about 3 Torr in the vessel when the vessel has been evacuated; a CVD reaction chamber in which a substrate is to be supported for coating with film of the metal or compound of the metal by a CVD reaction of the precursor; a gas conducting passage extending from the evaporation vessel and having an outlet connected to an inlet of the CVD reaction chamber, the passage having a flow restriction orifice therein, the passage being of sufficiently wide diameter to so as to insignificantly affect the pressure drop across the tube of vapor flowing through the orifice; and a flow control device connected to the passage upstream of the orifice and having a programmed controller connected thereto, the controller being programmed to control the flow of the precursor vapor from the outlet of the passage accordance with stored flow characteristic data to maintain a flow of vapor of the precursor from the evaporation vessel to the CVD chamber via the orifice and passage to deliver precursor vapor to the CVD chamber at a flow rate that will provide for the deposition of the film at a predetermined production rate 00/65127

- 25 -

15. The apparatus of claim 14 wherein:

16. The apparatus of claim 14 wherein:

17. The apparatus of claim 14 wherein: the heater is controllable to heat a titanium halide precursor to a vapor pressure of at least about 3 Torr.

18. The apparatus of claim 14 wherein: the programmed controller is programmed to control the flow of the precursor vapor from the outlet of the passage accordance in a predetermined relationship to the upstream and downstream pressures across the passage over a predetermined production rate flow range and modifying the relationship in accordance with tabulated data stored in response to calibration of the flow characteristics of the passage.