US3892650A

US3892650A - Chemical sputtering purification process

Info

Publication number: US3892650A
Application number: US319409A
Authority: US
Inventors: Jerome J Cuomo; Jr Walter W Molzen
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1972-12-29
Filing date: 1972-12-29
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01

Abstract

A process for purifying the diffuse sputtering region of a sputtering system by providing therein a readily disproportionated active vapor species which decomposes therein to form an active getterer of undesirable reactive gases, such as desorbed and source sputtering gases present in the system. In one example, silane mixed with argon decomposes in the diffuse sputtering region to form films of silicon and compounds thereof throughout the sputtering chamber, which silicon acts to chemically getter the reactive gases present. Using an ultra pure vanadium target, films of vanadium are produced having bulk superconducting and resistivity properties.

Description

United States Patent [191 Cuomo et al.

1 July 1,1975

[ CHEMICAL SPUTTERING PURIFICATION PROCESS [75] Inventors: Jerome J. Cuomo, Bronx; Walter W. Molzen, Jr., Patterson, both of NY.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

22 Filed: Dec. 29,1972

21 Appl.No.:319,409

[52] US. Cl 204/192; 204/298 [51] Int. Cl. C231: 15/00 [58] Field of Search 204/192 [56] References Cited UNITED STATES PATENTS 3,294,669 12/1966 Theuerer 204/192 3,563,873 2/1971 Beyer 204/192 3,655,438 4/1972 Sterling et a1 204/192 3,783,119 1/1974 Gregor et a1 204/192 OTHER PUBLICATIONS Getter Sputtering for the Preparation of Thin Films of Superconducting Elements and Compounds", H. C. Theuerer et al., Journal of Applied Physics, Vol. 35,

No. 3, (2 parts-part 1) pp. 554-555, March 1964.

Superconductive Films Made by Protected Sputtering of Tantalum or Niobium", Journal of Applied Physics, Vol. 33, N0. 5, p. 1898, 1962, by Frerichsw Primary Examiner0scar R. Vertiz Assistant ExaminerWayne A. Langel Attorney, Agent, or FirmJohn A. Jordan I 57] ABSTRACT A process for purifying the diffuse sputtering region of a sputtering system by providing therein a readily dis-- proportionated active vapor species which decomposes therein to form an active getterer of undesirable reactive gases, such as desorbed and source sputtering gases present in the system. In one example, silane mixed with argon decomposes in the diffuse sputtering region to form films of silicon and compounds thereof throughout the sputtering chamber, which silicon acts to chemically getter the reactive gases present. Using an ultra pure vanadium target, films of vanadium are produced having bulk superconducting and resistivity properties.

13 Claims, 1 Drawing Figure 1 CHEMICAL SPUTTERING PURIFICATION PROCESS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sputtering processes. More particularly, the present invention relates to a chemical sputtering purification process, whereby high purity materials, such as films of vanadium or niobium, may be produced.

2. Description of the Prior Art In the process of sputtering pure materials, various techniques are known to aid in attempting to achieve high purity levels. Achieving high purity materials through sputtering depends, to great extent, upon system preconditioning, substrate bias, and general care in choosing gas and target material purity. In particular, it has been shown that pure, and in some cases ultra pure, materials can be sputtered by presputtering with gaseous materials that are active getterers of the undesirable reactive gases present in the sputtering system, and by bias sputtering. Bias sputtering provides a bombardment mechanism of the substrates, which mechanism has been described as a scrubbing" of the depositing surface which acts to desorb loosely held species. Another approach to obtaining high purity materials using the sputtering process, involves the ultra high vacuum techniques of system baking and prepump down pressures of about l X Torr.

Still another approach to obtaining high purity materials using the sputtering process involves getter sputtering techniques. Getter sputtering techniques were developed to eliminate the need for ultra high vaccum systems. Such techniques are described, for example, in an article entitled, Getter Sputtering for the Preparation of Thin Films of Superconducting Elements and Compounds, by H. C. Theuerer et al., Journal of Applied Physics, Vol. 35, No. 3, (2 parts part I) pp. 554-5, March, I964. Another approach which obviates the need of ultra high vacuum techniques, involves a form of back-sputtering operation. An arrangement for carrying out this latter type of sputtering is described by Rudolf Frerichs in an article entitled, Superconductive Films Made by Protected Sputtering of Tantalum or Niobium, Journal of Applied Physics, Vol. 33, No. 5, p. 1898, 1962.

The difficulties and disadvantages in prior art techniques used to obtain high purity materials in sputtering systems resides in the fact that prolonged and sometimes elaborate preconditioning processes are required to prepare the sputtering environment. Still other prior art techniques for obtaining high purity films require somewhat elaborate and cumbersome sputtering apparatus. Accordingly, in the prior art of sputtering high purity materials, considerable steps were taken to reduce the undesirable reactive species from the sputtering environment. The need to reduce or eliminate reactive species from the sputtering environment is particularly acute where efforts are being made to sputter one or more of the more chemically active elements, such as vanadium, niobium. scandium, and the like.

SUMMARY OF THE INVENTION In accordance with the principles of the present invention, there is provided a relatively simple and effective process for purifying the sputtering environment. More particularly. in accordance with the present invention, a process is provided for chemically purifying the sputtering environment by providing within the diffuse sputtering region an active vapor species which acts to chemically getter undesirable reactive species therein, such as reactive gases and the like. Any active vapor species which is easily disproportionated, and which is chemicaly reactive with at least one undesirable species present in the sputtering environment, may be employed. A relatively small percentage of the active vapor species is mixed with the inert sputtering environment species employed. For example, concentrations of the active vapor species ranging between 0.l and 10% may be used, depending upon the relative sputtering rate employed. Typical sputtering pressures range between l X 10 to l X 10 Torr. The active vapor species is decomposed in the sputtering environment to form an active gettering species which in turn acts to getter desorbed and source sputtering gas contaminants in the sputtering environment. The mild diffuse plasma region existing around and outside of the material deposition region acts to readily decompose, react and deposit on the walls, the active vapor species present in the system, prior to its reaching this deposition region.

In a specific example, silane (SiI-h) is employed as the active vapor species in an argon environment, for sputtering films of vanadium, and the like. The silane decomposes to form an active silicon species, which, in turn, acts as a getterer.

It is, therefore, an object of the present invention to provide an improved sputtering process.

It is a further object of the present invention to provide a relatively simple technique for purifying sputtering environments.

It is yet a further object of the present invention to provide a relatively simple process for purifying sputtering environments, whereby pure materials may readily be sputtered.

It is yet still a further object of the present invention to provide a chemical sputtering purification process.

It is still another object of the present invention to provide a sputtering process whereby relatively simple and conventional sputtering apparatus which reach conventional vacuum levels may be employed to fabricate high purity materials, by introducing a chemical gettering agent into the sputtering environment.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a schematic representation of a sputtering system, to be used in the description of the process and apparatus therefor, in accordance with the principles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The schematic representation of the FIGURE depicts an RF sputtering system, typical of those that may be employed in practicing the present invention. As shown in the FIGURE, RF source I is coupled to target holder assembly holder 3, via impedance matching network 5 and capacitor 7. Impedance matching network 5 is employed to match the impedance of the system to the impedance of source 1.

As is known to those skilled in the art, it is possible to control, to some degree, the purity of sputtered films by applying a bias voltage to the substrate upon which the target is to be sputtered. Accordingly, there is provided, in the particular sputtering system shown in the FIGURE, a typical biasing network comprising ac. impedance elements 9, 11, and 13. These elements act to insure that an appropriately selected bias is applied on substrate 15. In this regard, it should be recognized that relatively simple d.c. bias techniques may be employed where sputtering is to occur upon a substrate exhibiting relatively good conductive characteristics. However, on the other hand, where the substrate to be employed does not exhibit relatively good conductive characteristics, a.c. biasing methods may be employed, as shown in the RF system of the FIGURE,

Although there are any of a variety of ac. circuit techniques that may be employed to bias the substrate used for sputtering, the RF driven biasing arrangement shown has been found to be particularly effective. As can be seen, inductor 9 is coupled at one end point thereof to the node between impedance matching network 5 and capacitor 7, and at an intermediate point thereof, to movable wiper arm l7. The midpoint of conductor 9 is grounded, while the remote end 19 is left floating, with wiper arm 17 acting to provide a complete path, the impedance of which varies in accor dance with the wiper arm position.

As shown in the FIGURE, wiper arm 17 is coupled to variable capacitor 11 and variable inductor 13, with the latter element being coupled to capacitor 21. Also shown in the FIGURE is meter 23 arranged to be coupled to the junction of capacitor 21 and anodic substrate holder 25, via conductor 27. This meter is employed to measure half the peak-topeak or applied d.c. voltage on the anodic substrate holder. ln this regard, inductor 27 and capacitor 29 are employed to isolate the meter from the RF substrate biasing network.

It should be understood that although a specific sput tering arrangement and attendant particular biasing network have been shown, any of a variety of sputtering arrangements and biasing networks, and the like, may be employed in practicing the present invention. In the particular RF substrate biasing network shown, the grounded center tap inductor 9 acts to invert the RF voltage, so that when the RF signal from source 1 is positive, for example, the voltage between the grounded center tap and the floating end is negative. In this regard, wiper arm 17 may be varied selectively to vary the amplitude of the inverted voltage. Variable capacitor 11 and variable inductor 13 are employed to selectively tune the biasing network arrangement. Ac cordingly, it can be seen that the degree of phase shift may be varied over 360 by varying capacitor ll and inductor 13. With such an arrangement, both the am plitude and phase of the RF substrate bias may readily be adjusted. The significance of being able to readily adjust phase and amplitude will be appreciated when it is recognized that the RF load, i.e., the impedance of the sputtering system, varies in accordance with the parameters of the sputtering system. Accordingly, where it is desirable to obtain a maximum or peak-topeak voltage on the substrate, for a given wiper arm setting, the tuning circuit may be adjusted to resonance,

whereby matching between the impedance of the sputtering system and inductor 9 is readily obtained.

It should be understood that, although not a part of the present invention, the practical advantage of em ploying the RF driven substrate biasing arrangement shown resides in the fact that a more controllable biasing level on the substrate is more accurately and readily obtained and adjusted, independent of target potential. In this regard, it should be appreciated that the purpose of substrate biasing is to provide a mechanism for substrate sputtering, whereby over a portion of the RF operating cycle, bombardment of the substrate occurs. Although the substrate biasing technique and resultant bombardment of the target are not essential to the practice of the present invention, such a technique does aid in reducing impurities and effecting a redistribution of atoms, such that the loosely bonded atoms sputtered thereon are removed. Typically, in this regard, voltage values for the system shown may involve, for example, a target voltage of approximately i000 volts, and an RF driven substrate bias of up to several hundred or more volts.

Substrate 15, shown in the FIGURE mounted on substrate holder 25, may be any of a variety of substrate materials, as is well known to those skilled in the art. In accordance with the principles of the present invention,,target 26 may be any of the variety of high purity target materials desired to be sputtered onto substrate 15. Target holder assembly 3, which is in conductive and thermal contact with target 26, may be water cooled with the water entering and exiting in accordance with the arrows shown at the top of the assembly. Surrounding both the cathodic target holder assembly 3 and pedestal portion 51 of anodic substrate holder 25, are a pair of Helmholtz coils 31. In this regard, coils 31 act to provide a magnetic field of approximately 30-80 gauss perpendicular to the plane of target 26 and substrate 15. The function of this magnetic field is to increase the concentration of electrons in the sputtering region, so that the sputtering efficiency will be increased. Moreover, the magnetic field also acts to increase, to some extent, the bias on the substrate. Grounded shield 33, around target 26, acts to limit and focus the sputtering of target 26 to the central portion thereof.

The pair of

ceramic sleeves

37 and 39 act to insulate the cathodic target holder assembly 3 from the metal sputtering chamber 41 and housing portion 35a of mount 35, respectively. In order to maintain substrate 15 at the desired temperature, a heating assembly 43 is provided. To maintain the area surrounding the substrate holder 25 cool, cooling coils, such as those shown at 45, may readily be employed. To facilitate presputtering steps, a shutter arrangement 47 is provided to be movably positionable between substrate 15 and target 26. As can be seen in the FIGURE. turning assembly 49, external to chamber 41, acts to accomodate removal of the shutter from the region between substrate 15 and target 26. As shown, the pedestal portion 51 of the anodic substrate holder is mounted upon insulation 53, so as to thereby electrically isolate the substrate holder assembly from metal chamber 41.

To aid in obtaining high purity sputtered materials, sputtering chamber 41 is equipped with a titanium sublimation pump 55, surrounded by a liquid nitrogen shroud 57. As is known to those skilled in the art, the sublimation pump acts to getter active species, such as oxygen and oxygen-bearing compounds, and the like, from within the chamber onto the surface of the cryogenically cooled drum 59 of the pump, before sputtering begins. Titanium filament 61 may be energized via an electrical source coupled to the external wires extending therefrom. Typically, port 63 may be used to pass the high purity gas employed, through the titanium pump and into the sputtering chamber. By passing the high purity gas through the titanium pump, the gas becomes even further purified.

THE PROCESS In accordance with the principles of the present invention, any of a variety of high purity target materials may be used as the target 26. Because the process of the present invention acts quite simply and effectively to provide a high purity environment, some ofthe more reactive target materials may be employed to sputter high purity thin films, and the like, on to the substrate. For example, vanadium, niobium, tantalum, and compositions thereof, may readily be sputtered in accordance with the process of the present invention. Likewise, iron, cobalt, nickel, scandium, yttrium, and the lanthanide series may readily be sputtered. In addition, the actinide series, and the like, may be sputtered, in accordance with the process of the present invention. The difficulties typically encountered in sputtering these materials, are well known to those skilled in the art.

Typically, the system employed in accordance with the principles of the present invention is prepared for a sputtering operation by initially prepumping the sputtering chamber 41 down to a pressure of from 2.0 to 8.0 X Torr, with substrate 15, upon which sputter ing is to occur, being maintained at the desired substrate operating temperature. The prepumping may be achieved by any of a variety of conventional pumping arrangements. Accordingly, for the sake of simplicity, the pumping operation has only been shown by the legend vacuum at the lower right hand portion of chamber 4i.

It should be appreciated that by empioying the active vapor species to provide a chemical getterer in accordance with the present invention, as will be described in more detail hereinafter, the prepumping operation to prepare the system for high purity sputtering is simplified. It should be noted in this regard, that in order to achieve the level of purity obtained by the process of the present invention, it is normally necessary to maintain a higher vacuum level for a longer period of time. Thus, in the present invention, to prepare the system for sputtering, it is only necessary that the system be prepumped to l0 to 10 Torr, at most, and this vacuum level be maintained for a matter ofa few minutes. To achieve the same level of purity without the active vapor species provided by the present invention, it is necessary to prcpump to a level of around 10 Torr, and maintain this level for relatively long periods of time, ie, tens of minutes. The reason for the latter vacuum constraints will be understood when it is recognized that in order to clean up the chamber, it is necessary that the vacuum system employed exceed the outgassing rate and act to provide a net reduction of the level of impurity in the system. On the other hand, the method in accordance with the principles of the present invention acts to reduce the outgassing itself and, accordingly, obviates the need for total dependence on the vacuum system for cleaning the sputtering chamber.

During the prepumping operation, titanium filament 6] acts in combination with the cryogenically cooled evaporated film on drum 59 to getter active species, such as oxygen and oxygen-bearing compounds from within the system. After the system has been sufficiently pumped down and maintained at the desired vacuum level, the system is next back filled with a high purity argon having mixed therein an active vapor species, in accordance with the present invention. The high purity argon with active vapor species may, if desired, be admitted via port 63. With this gas mixture ad mitted into the system via port 63, it is passed through the titanium sublimation pumping arrangement whereby oxygen, oxygen-bearing compounds, nitrogen, and the like, may be removed from the argon mixture.

It should be noted that when the argon mixture is admitted into the sputtering chamber through the titanium sublimation pumping arrangement, a certain amount of the active vapor species mixed therewith, may be gettered out. Accordingly, whether the argon mixture is passed through the titanium sublimation pumping arrangement, depends upon the particular ap plication employed. It might be preferable in certain applications that the argon mixture be admitted into the system via another port, which will not act to pass the gas through the titanium sublimation pump. Thus, where a high purity argon having mixed therewith silane, for example, is employed, it might be preferred to admit the gas into the chamber, in accordance with this latter approach.

in accordance with the preferred mode of practicing the invention, then, a high purity inert sputtering gas species having mixed therewith selected active vapor species is admitted into the sputtering chamber, via port 64, until a pressure of approximately 10 Torr is reached. in this regard, it should be noted that the argon and active vapor species may be entered into the sputtering chamber either separately, or in a premixed state. Thus, port 64 could be employed to first enter the argon and then the active vapor species, or vice versa. On the other hand, separate ports could be used for each gas. However, in a preferred mode, a single port, such as 64, is employed to enter a premixture of argon and the active vapor species from a single container.

It should be understood, however, the significance of the present invention does not reside in the exact manner by which the active vapor species is entered into the sputtering chamber, but rather in the fact that the active vapor species is present in the sputtering chamber. In this regard, it should be further understood that the active vapor species is selected, in accordance with the particular application. The conditions for selecting the active vapor species are that it exhibit a chemical reactivity with at least one of the undesirable species present in the system, and that it be readily disproportionated, particularly as pertains to being readily disproportionated by way of a relatively weak plasma. In addition to being readily disproportionated and chemi cally reactive with at least one of the undesired species, the active vapor species must be present in concentrations sufficiently low so as to not be allowed to penetrate the region between the sputtering electrodes, and yet sufficiently high so as to provide adequate gettering. ln this regard, where the sputtering rate is, on the one hand, approximately 5 A/sec. the active vapor species may be present in amounts as low as 0.1%. On the other hand, where the sputtering rate is approximately 50 A/sec, the active vapor species may be present in concentrations as high as 10%.

It should be understood, that the function of the active vapor species is to decompose and provide an active gettering species, which is available for gettering the desorbed and source sputtering gasses in the system. For example, where vanadium is being sputtered onto a substrate, a mixture of argon and silane may be employed. As the silane enters the sputtering chamber, it decomposes to form an active silicon species which acts to getter desorbed and source sputtering gases in the chamber. In this regard, the silane decomposes before it reaches the active film growth area, since it is readily activated by the mild diffuse plasma region existing around and outside of the film deposition area, between the sputtering electrodes. As the silane decomposes, the resultant silicon and reacted silicon species deposit upon the internal surfaces of the sputtering chamber. Accordingly, substantially the entire internal surface of the sputtering chamber becomes coated with a thin film of silicon and compounds thereof. The silicon in this manner, then, acts to react with and trap the desorbed and source sputtering gases, thereby substantially reducing the outgassing rate.

Prior to actual sputtering, it may be desired to perform a presputtering operation in the argon and active vapor species mixture. Although the presputtering step is not essential in accordance with the process of the present invention, in the preferred mode it might be desirable to utilize this process so as to insure the utmost purity within the system. It should be noted that the system may be energized with an RF source sufficient in power to deliver in the neighborhood of around 8 watts/cm to the target. Where a typical target of roughly 10 cm is employed, roughly 100 watts of power would be sufficient to provide effective sputtering. However, it is clear that the amount of power re quired to be delivered to the system is not critical, and varies in accordance with the particular sputtering parameters employed in a given application.

In the presputtering operation, the shutter arrangement (which is grounded via the walls of chamber 41) is first positioned between the target and the substrate by knob 49, so as to obstruct deposition onto the substrate, as shown in the FIGURE, when the system power is turned on. Thus, with the argon and active vapor species mixture present in the chamber and the system power turned on, a plasma is generated and the high purity target is sputtered upon shutter 47. This presputtering time may range from 5 to 30 minutes.

After the target is presputtered on to the shutter 47, the system may then be prepared for sputter cleaning substrate 15. However, sputter cleaning substrate 15 is a matter of choice, and is not an essential operation. To sputter clean substrate 15, adjustments are made in the biasing network so as to produce a dc. level bias on substrate 15. A dc. bias level of approximately 150 volts has been found satisfactory. With shutter 47 in conductive contact with shield 33, which shield is grounded via the walls of mount 35 and chamber 47, sputter cleaning of the substrate is effected for 5 to it) minutes.

After presputtering, the system is ready to sputter any of a variety of materials. as hereinabove men tioned. It has been found, for example, that in sputtering vanadium from an ultra pure vanadium target, using a mixture of argon and from 0.1 to 10% silane, pure films of vanadium are produced having bulk superconducting and resistivity properties. The process was repeated with niobium having, however, the addition of a few percentage of oxygen to test the process. Similar results of pure films were obtained.

In the above processes, the silane decomposed to form a film of silicon compounds, deposited over the internal surface of the sputtering chamber. However, in the region of interest between the sputtering electrodes, no silicon was detectable. The absence of silicon within the sputtering region between targets 26 and substrate 15 is due to the fact that the argon based plasma produced therebetween, particularly at the pcriphery thereof, acts to quickly break down the silane before it has an opportunity to significantly penetrate this plasma zone. This latter fact is evidenced by the relatively rapid gradation in silicon deposits on the substrate across the barrier wall of the plasma, whereby the silicon deposits vanish rather markedly. On the other hand, silicon deposits exist rather uniformly throughout the various surfaces, internal to chamber 21. For example, the outer surface of the walls of mount 35, and the inner surface of the vertical walls of the chamber through which

ports

63 and 64 penetrate, are generally uniformly coated with silicon, or silicon compounds.

It should be appreciated that although silane is known in the art for purposes of sputtering silicon layers upon a substrate, silane has not been employed as an active vapor species to provide a gettering agent effectively operative within the sputtering environment to reduce outgassing, and the like. Reference is made to US. Pat. No. 3,647,663 for a description of the manner by which silane may typically be employed to fabricate, for example, layers of silicon oxide on a substrate.

Although silane has been found to be a particularly effective vapor species, it should be understood as hereinabove mentioned, that any of a variety of vapor species may, as readily be employed. For example, titantium tetrachloride (TiCh) may be mixed with argon, for example, to provide an active gettering mechanism for removing impurities in the fabrication of ultra pure materials. Titanium tetrachloride would readily decompose in the sputtering chamber, into a titanium gettering species, whereby water vapor, nitrogen, oxygen, carbon and the like would be gettered.

Likewise, tungsten hexafluoride (WF,,) may be employed as the active vapor species in accordance with the principles of the present invention. In addition, uranium hexafluoride (UF.,) could be employed as the active vapor species, in accordance with the present invention. Each of these species, mixed in concentration of from 0.1 to 10% in argon would readily be dispro portionated in the sputtering environment to provide an active gettering species (W and U) for gettering water vapor, nitrogen, oxygen, carbon, and the like, during the sputtering of any of a variety of ultra pure materials.

It is evident that, in accordance with the principles of the present invention, an active gettering species is cfectively provided in the sputtering environment to re duce the outgassing rate, whereby a purification level is obtained therein without prolonged preconditioning and presputtering periods of time. In addition, this purification level is maintained during the sputtering pro cess with a minimum of system resources. As a result of employing such techniques, relatively high purity materials are obtained with a minimum of steps.

Typically. preconditioning periods for prepumping and presputtering of from 5 to 15 minutes are sufficient to provide high purity materials. Moreover, pressure ranges from 1 X 10' to l X 10 Torr are sufficient to produce the high purity materials. using a conventional sputtering system configuration.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A process for purifying a sputtering chamber, comprising the steps of:

procuring an active vapor species selected from the group consisting of SiH,, TiCh, WP and UT", which active vapor species is readily disproportionated by the plasma generated within the diffuse sputtering region of said sputtering chamber during sputtering;

positioning a substrate and source material in said sputtering chamber so that said source material may be sputter deposited upon said substrate; evacuating said sputtering chamber; introducing into said sputtering chamber an inert sputtering atmosphere including the procured active vapor species mixed therewith in an amount of from 0.l to 10% by volume of said atmosphere; and

generating a plasma from said atmosphere including generating a diffuse plasma in said sputtering region around and outside the active deposition region between said source material and said substrate by applying an RF source of sputtering power to said substrate and source material under conditions such that said procured active vapor species is decomposed therein by said diffuse plasma before reaching said active deposition region to thereby form an active gettering species to coat the interior of said chamber and thereby reduce the outgassing rate thereof.

2. The process as set forth in claim 1 wherein the said step of evacuating comprises evacuating said chamber to a level of approximately l" Torr or less.

3. The process as set forth in claim 2 wherein said inert sputtering atmosphere is argon.

4. The process as set forth in claim 3 wherein said source material is selected from the group consisting of vanadium, niobium, tantalum, iron, cobalt, nickel, scandium, yttrium, and the lanthanide series.

5. The process as set forth in claim 1 wherein said source material is selected from the group consisting of vanadium and niobium.

6. The process as set forth in claim 5 wherein the said step of intr ducing into said chamber comprises introducing said inert sputtering atmosphere to a pressure between and 10' Torr.

7. A process for sputtering high purity materials, comprising the steps of:

positioning within a sputtering chamber a target material and substrate upon which said target material is to be sputtered; evacuating said sputtering chamber; providing an RF sputtering potential between said target and substrate sufficient to effect an ionization within the deposition region between target and substrate to produce target material deposition upon said substrate at a rate between approximately SA/sec and SOA/sec; procuring an active vapor species selected from the group consisting of SiH TiCl WP and UF which active vapor species will be readily disproportionated in the diffuse plasma produced within said chamber outside said deposition region; and

introducing into said chamber an inert sputtering atmosphere of argon having mixed therewith from 0.1 to lO% by volume of said procured active vapor species, said inert sputtering atmosphere of argon becoming ionized therein through stimulation by said RF sputtering potential to produce said diffuse plasma around and outside said deposition region under conditions such that said procured active vapor species is decomposed before reaching said deposition region so as to form an active gettering species to thereby reduce the outgassing rate re quired to maintain a given level of purity.

8. The process as set forth in claim 7 wherein said step of evacuating comprises evacuating said sputtering chamber to a pressure level of approximately l0 Torr or less for a relatively short period of time.

9. The process as set forth in claim 8 wherein after said step of evacuating said sputtering chamber, said sputtering chamber is back-filled with said inert sputtering atmosphere of argon having mixed therewith said procured active vapor species to a pressure level between 10" and 10" Torr.

10. The process as set forth in claim 7 wherein said inert sputtering atmosphere of argon is introduced into said chamber to a pressure level of between l0 and l0 Torr.

11. The process as set forth in claim 10 wherein said step of introducing into said chamber said inert sputtering atmosphere of argon having mixed therewith from 0.1 to 10% by volume of said procured active vapor species comprises premixing said procured active vapor species with said inert sputtering atmosphere of argon and admitting the mixture thereof into the evacuated sputtering chamber to said pressure level.

12. The process as set forth in claim 7 wherein said target material is selected from the group consisting of vanadium and niobium and wherein said procured active vapor species is SiH 13. The process as set forth in claim 7 wherein said target material is selected from the group consisting of vanadium and niobium and wherein said procured active vapor species is TiCL.

Claims

1. A process for purifying a sputtering chamber, comprising the steps of: procuring an active vapor species selected from the group consisting of SiH4, TiCl4, WF6, and UF6 which active vapor species is readily disproportionated by the plasma generated within the diffuse sputtering region of said sputtering chamber during sputtering; positioning a substrate and source material in said sputtering chamber so that said source material may be sputter deposited upon said substrate; evacuating said sputtering chamber; introducing into said sputtering chamber an inert sputtering atmosphere including the procured active vapor species mixed therewith in an amount of from 0.1 to 10% by volume of said atmosphere; and generating a plasma from said atmosphere including generating a diffuse plasma in said sputtering region around and outside the active deposition region between said source material and said substrate by applying an RF source of sputtering power to said substrate and source material under conditions such that said procured active vapor species is decomposed therein by said diffuse plasma before reaching said active deposition region to thereby form an active gettering species to coat the interior of said chamber and thereby reduce the outgassing rate thereof.

2. The process as set forth in claim 1 wherein the said step of evacuating comprises evacuating said chamber to a level of apProximately 10 7 Torr or less.

6. The process as set forth in claim 5 wherein the said step of introducing into said chamber comprises introducing said inert sputtering atmosphere to a pressure between 10 4 and 10 1 Torr.

7. A PROCESS FOR SPUTTERING HIGH PURITY MATERIALS, COMPRISING THE STEPS OF: POSITIONING WITHIN A SPUTTERING CHAMBER A TARGET MATERIAL AND SUBSTRATE UPON WHICH SAID TARGET MATERIAL IS TO BE SPUTTERED, EVACUATING SAID SPUTTERING CHAMBER, PROVIDING AN RF SPUTTERING POTENTIAL BETWEEN SAID TARGET AND SUBSTRATE SUFFICIENT TO EFFECT AN IONIZATION WITHIN THE DEPOSITION REGION BETWEEN TARGET AND SUBSTRATE TO PRODUCE TARGET MATERIAL DEPOSITION UPON SAID SUBSTRATE AT A RATE BETWEEN APPROXIMATELY 5A/SEC AND 50A/SEC, PROCURING AN ACTIVE VAPOR SPECIES SELECTED FROM THE GROUP CONSISTING OF SIH4 TICL4, WF6 AND UF6 WHICH ACTIVE VAPOR SPECIES WILL BE READILY DISPROPORTIONATED IN THE DIFFUSE PLASMA PRODUCED WITHIN SAID CHAMBER OUTSIDE SAID DEPOSITION REGION, AND INTRODUCING INTO SAID CHAMBER AN INERT SPUTTERING ATMOSPHERE OF ARGON HAVING MIXED THEREWITH FROM 0.1 TO 10% BY VOLUME OF SAID PROCURED ACTIVE VAPORT SPECIES, SAID INERT SPUTTERING ATMOSPHERE OF ARGON BECOMING IONIZED THEREIN THROUGH STIMULATON BY SAID RF SPUTTERING POTENTIAL TO PRODUCE SAID DIFFUSE PLASMA AROUND AND OUTSIDE SAID DEPOSITION REGION UNDER CONDITIONS SUCH THAT SAID PROCURED ACTIVE VAPOR SPECIES IS DECOMPOSED BEFORE REACHING SAID DEPOSITION REGION SO AS TO FORM AN ACTIVE GETTERING SPECIES TO THEREBY REDUCE THE OUTGASSING RATE REQUIRED TO MAINTAIN A GIVEN LEVEL OF PURITY.

8. The process as set forth in claim 7 wherein said step of evacuating comprises evacuating said sputtering chamber to a pressure level of approximately 10 7 Torr or less for a relatively short period of time.

9. The process as set forth in claim 8 wherein after said step of evacuating said sputtering chamber, said sputtering chamber is back-filled with said inert sputtering atmosphere of argon having mixed therewith said procured active vapor species to a pressure level between 10 4 and 10 1 Torr.

10. The process as set forth in claim 7 wherein said inert sputtering atmosphere of argon is introduced into said chamber to a pressure level of between 10 4 and 10 1 Torr.

12. The process as set forth in claim 7 wherein said target material is selected from the group consisting of vanadium and niobium and wherein said procured active vapor species is SiH4.

13. The process as set forth in claim 7 wherein said target material is selected from the group consisting of vanadium and niobium and wherein said procured active vapor species is TiCl4.