MXPA98010595A - Vacuum tuner system for purifying the working atmosphere in the deposition processes of va - Google Patents

Abstract

A system formed of one or more vacuum tuning devices in the form of synthesized bodies of vacuum tuning powders or deposits of vacuum tuning material on a metal support, to be arranged in the working area of the process chambers, is described. for the deposition of thin layers of metallic or ceramic materials of vapors or plasmas to purify the gaseous atmosphere contained in this

Description

VACUUM TUNER SYSTEM TO PURIFY THE WORKING ATMOSPHERE IN STEAM PHYSICAL DEPOSITION PROCESSES DESCRIPTION OF THE INVENTION The present invention relates to a vacuum tuning system for purifying the working atmosphere in physical vapor deposition processes. The processes of deposition of thin layers of metallic or ceramic materials of suitable vapors or plasmas are more and more widely used in industry, and are generally referred to in the field by the English term "Physical Vapor Deposition" (Physical vapor deposition). ", or by its acronym PVD These processes are used, for example in the field of semiconductors to deposit a number of layers, which are then selectively removed to obtain the integrated circuits, or in the compact disc industry to form the reflective layer In all these processes, high purity is required for spent gases, particularly in the production of semiconductors, impurities in process gases result in micro-imperfections in electronic devices, and the smaller the size of the devices, the greater the effect of such imperfections in the performance of such devices. To reduce the average size of these devices, it is necessary to use a more and more pure process gas in order to reduce the percentage of waste.

The use of vacuum tuning materials combined with conventional pumps to purify upstream gases with respect to PVD processes is a common practice in the industry so far. However, the purity control of inlet gases in the production lines is not enough, since the impurities can enter the working atmosphere resulting from the degassing of the materials that form the walls or other parts of the chamber. In particular, some processes such as deposition of titanium or aluminum nitride layers can result in contamination. These depositions are made by the technique known by the English term "sputtering" (crackling), where a flat surface of a "target", consisting of the material to be deposited, is worn out due to the impact of ions of heavy atoms (usually Ar + ions) accelerated by a suitable electric field; the particles removed from the target surface are deposited in the form of thin layers on the substrate of semiconductor material, being generally arranged in a parallel manner with respect to the target surface. The gases in the target, for example, mechanically included in the structure of the material during its production, are discharged during the sparking process, resulting in a high concentration of impurities in the work area. The most common among the impurities are H2O, H2, CO, CO2 and CH4, and their concentration can vary, depending on the specific characteristics of each process, from approximately 1 to 100 ppm.

Patent applications left open WO 96/13620, WO 96/17171, EP 693626 and WO 97/17542 relate to gas that purifies with vacuum tuner pumps arranged within the PVD chambers. These applications describe vacuum tuner pumps being arranged inside the chambers in potions away from the work areas. The main advantage obtained by using these pumps in situ is the reduction of the dead times which are necessary to bring the level of impurities below a predetermined value, after each opening of the chamber, for example, for maintenance operations. However, these systems do not solve, or solve only partially, the problem due to impurities in the work area during PVD operations, since this area is defined by screens that act in order to prevent the target material from being deposited on unwanted portions of the camera, such as, for example, feeding paths, openings to connect the camera to gas lines, etc. These screens have the lateral effect of greatly reducing the conductance of the gas between the work area and the remaining volume of the chamber, thus producing two different gaseous atmospheres inside the process chamber, so that the absorption of impurities in the area of work by the aforementioned on-site vacuum tuning pumps is negligible. Thus, the problem of an effective purification of the working atmosphere during the PVD process and of the contamination resulting from the layers deposited on a support by these processes is still not resolved.

The aim of the present invention is to provide a vacuum tuning system for purifying the gaseous atmosphere in the work area in physical vapor deposition processes. This objective is achieved according to the present invention by a vacuum tuning system formed of one or more essentially flat vacuum tuning devices being inserted within the working area of a process chamber for physical vapor deposition, in such arrangement that said vacuum tuner devices are essentially parallel and separate apart from the screens defining said work area and the space between the vacuum tuner devices and the screens is connected to the work area, said tuner devices being vacuum so that at least the surface facing the screens is made of vacuum tuning material. The invention will be described hereinafter with reference to the drawings, in which: - Figure 1 shows in a diagrammatic form a process chamber for physical vapor deposition; - Figure 2 shows the contour of the placement of the vacuum tuner system inside the process chamber of Figure 1; - Figures 3 and 4 show some embodiments of a first type of vacuum tuning devices, which can be used in the system of the invention; - Figure 5 shows a possible vacuum tuner system of the invention formed of devices of Figure 3; - Figure 6 shows a possible alternative mode of a second type of vacuum tuning devices, which can be used in the system of the invention; - Figure 7 shows another possible vacuum tuner system of the invention formed of devices of Figure 6. With reference to Figure 1, a process chamber is shown diagrammatically for the production of integrated devices. A chamber 10 is formed of a housing 1 1 defining a space 12 isolated from the atmosphere. The chamber has connected to it a pumping system for its evacuation, which is generally indicated in Figure 13, and at least one feeding line for the process gas, which is generally indicated as 14. Inside the chamber 10 is a target 15, being generally disk-shaped or a short cylinder and made of material 16 to be deposited as a thin layer; a support 17 carrying a housing 18 for a substrate 19 made of a semiconductor material (generally silicon), to have the thin layer of material 16 deposited thereon; finally, there are screens 20, 20 ', ... (only two are shown in the Figure). The screens 20, 20 ', ... divide the space 12 into two areas, a work area 21 and an area 22 which has the auxiliary structures of the PVD process, such as the electrical connections or the inputs of the PVD processes. gas supply lines; Areas 21 and 22 have contact with each other only through a small conductance 23 on the edge of the screens. There is a wide variety of modifications to the simple scheme outlined above. For example, the work area 21 can be square, rectangular or cylindrical; in any case, generally the screens are essentially flat and are inserted inside the chamber 10 with the polygonal arrangement being the most adequate to define the desired geometry in the work area. The objective 15 can be made of a precursor of material 16 to be deposited on the substrate 19, or it can be part of a multi-objective system, which is used in some cases to allow the sequential deposition of layers of different materials without having have to open the camera The support 17 can be moved generally in a vertical direction to bring the substrate 19 into the working position, while the housing 18 is generally heated in order to maintain the substrate 19 at a temperature that is optimal to obtain a thin layer with good homogeneity properties; this temperature, depending on the material 16, generally varies from about 100 to 500 ° C. The vacuum tuner pumps of the known art are arranged in various positions within the chamber 10, however always in the area 22, and thus are practically isolated from the gaseous atmosphere of area 21 due to the small conductance between the areas 21 and 22. On the contrary, according to the present invention, the vacuum tuning system is arranged within the area 21 and thus is in an effective position to absorb impurities in this area. In particular, the vacuum tuning system according to the invention is formed of essentially flat vacuum tuning devices, which are secured to the screens so that they are essentially parallel with respect to the screens, there is a space between screens and vacuum tuner devices and such a space is connected to a work area 21; additionally, the vacuum tuner devices must be secured to the screens in order to have at least the surface facing the screens made of vacuum tuning material. Figure 2 shows in outline the arrangement of the vacuum tuner system of the invention within a PVD process chamber. A vacuum tuner system 24 is essentially parallel with respect to screens 20, 20 ', ... and defines a space 25 between said screens and the system 24. The system 24 is formed of vacuum tuning devices 26, 26'. , ...; Figure does not show means for securing devices 26, 26 'to screens 20, 20', ..., since such means are different depending on the specific type of vacuum tuning devices used, as described herein in ahead. The vacuum tuning system 24 has a work area having a surface 27 facing the work area 21 and a surface 28 facing the screens 20, 20 ', ...; at least one surface 28 must be made of a vacuum tuning material 29. The system 24 can be arranged around the work area in order to sweep an angle less than 360 °, but preferably it completely encloses the work area, thereby increasing the available surface of vacuum tuning material and the efficiency of impurity absorption. As previously stated, whatever the geometry of the work area, generally the screens are essentially flat, as well as vacuum tuning devices 26, 26 '.,, Forming the system according to the invention. Since the vacuum tuner system should sweep an angle less than 360 ° around the work area 21, it may consist of only a simple vacuum tuning device. However, as previously stated, the vacuum tuner system preferably sweeps a 360 ° angle around the work area, being in this case formed of several vacuum tuner devices, and generally of at least as many tuner devices as possible. empty like screens. The space 25 must be connected to the area 21. The condition of the connection between the space 25 and the area 21 can be observed in many ways, for example, by such vacuum tuner devices that the surface 27 is continuous and there is conductance between the area 21 and the space 25 in the areas 30, 30 'indicated in Figure 2. However, the required condition is observed by means of vacuum tuning devices 26, 26', ... shaped or arranged so that the surface 27 is discontinuous; in particular, it has been found that the best efficiency for removing impurities from area 21 is obtained when the surface 27 being effective, i.e., the sum of the surfaces facing area 21 for all vacuum tuner devices, is a fraction of the available surface for a continuous vacuum tuning system 24 ranging from 70 to 99%, and preferably from 80 to 95%. Surface discontinuities 27 may be in the form of holes-tracks in devices 26, 26 'or of empty spaces between adjacent devices; both possibilities are shown in the Figure, the discontinuities being indicated as 31, 31 ', .... In both cases, the discontinuities can have a regular or an irregular shape, and can be arranged in a regular or irregular manner in the available surface; for example, in the case of holes in the surface of a simple vacuum tuning device, they may be square or round, or irregular in shape, and may be arranged on the surface of the device as a network or random; in the case of separations between adjacent vacuum tuning devices, the shape and arrangement of the discontinuities depends on whether the devices 26, 26 ', ... are arranged in a regular manner on the available surface or not. Generally, regular forms and arrangements of discontinuities are preferred, both in simple vacuum tuning devices and between adjacent devices, as they are more suitable for automated production of vacuum tuning system 24 and allow easier control of the above-mentioned condition for the ratio between the effective surface and the available surface for the system 24. Mixed configurations are obviously possible, wherein the simple vacuum tuner devices have holes and the adjacent vacuum tuner devices are separated from one another . The distance between the vacuum tuner system 24 and the screens 20, 20 ', ... mainly depends on the total size of the area 21 and the distances between the adjacent vacuum tuner devices and / or the size of the holes in said dispositives. Generally, the distance between the vacuum tuner system and the screens varies from 1 mm to 5 cm; within these limits, said distance is generally smaller in small-sized PVD cameras, in order to prevent the vacuum tuner system from affecting the processes that occur in the work area; moreover, said distance increases with increasing distances between the adjacent vacuum tuner devices and / or the size of the holes in said devices. A wide variety of vacuum tuning materials can be used to produce the devices 26, 26 ', ..., including metals such as Zr, Ti, Nb, Ta, V, alloys between these metals or alloys of these metals and one or more elements selected from Cr, Mn, Fe, Co, Ni, Al, Y, La and rare earths, such as binary alloys Ti-V, Zr-V, Zr-Fe and Zr-Ni or ternary alloys Zr-Mn- Fe or Zr-V-Fe, or a mixture of the metals and previous alloys. The most commonly used vacuum tuning materials is the alloy having the weight composition Zr 84% - Al 16%, manufactured and sold by the SAES DE AFINADOR DE VACÍOS Company (Milan, ITALY) under the trademark St 101®; the alloy having the weight composition Zr 70% - V 24.6 & - Fe 5.4%, manufactured and sold by the Company SAES DE AFINADOR DE VACÍOS under the trademark St 707M, or mechanical mixtures of these two alloys and Zr or Ti; these mixtures are preferred due to their good mechanical properties, in particular with respect to the loss of particles. The vacuum tuning devices 26, 26 ', ... may be bodies made only of vacuum tuning material, obtained by sintering powder, or may consist of deposited vacuum tuning material, according to a variety of techniques , on the metal support. The production of sintered bodies from powders is known in the field of powder metallurgy, and generally comprises the steps of compressing the powders into a suitable mold and heating the coagulated powders until a partial melting of the surface of the grains is obtained. of dust. Modifications to the method in order to obtain bodies having specific characteristics, for example, being highly porous, are described, for example, in U.S. Patent 5324172 and in the patent application EP-A-719609, both in the name of the applicant , and in the patent application EP-A-765012. Figures 3 and 4 show vacuum tuner devices of this type. The device 35 of Figure 3 is rectangular in shape, and has on its ends openings-tracks 36,36 ', provided for the use of members such as screws and nuts to secure the device to the screens at the desired distance; it is obviously possible to use other means to secure the device to the screens, such as, for example, a metal member having a frame built into it to retain the vacuum tuner body and suitable spacers, which can be secured to the screens; the device 40 of Figure 4 is essentially square in shape and has a series of orifices-tracks 31, 31 ', ... which allow an easy connection between the work area 21 and the space 25, as previously mentioned. During the PVD process, the surface facing the area 21 is covered by the material 16 to be deposited as a thin layer on the substrate 19, while the surface 28 is active to absorb impurities. Since flat sintered bodies having side dimensions much larger than their thickness are complex to manufacture and have a low mechanical force, when these bodies are used for the vacuum tuning system of the invention, the latter is preferably formed of a relatively larger number of vacuum tuner devices, each having a considerably smaller surface area than the screen that holds them secured to it. An arrangement of this type is represented in Figure 5, which shows a portion of a screen 20 having secured thereto a plurality of devices 26, 26 ', 26", ... of type 35; devices 26, ..., are secured to the screen through suitable mounting members 37, 37 ', which also act as spacers .. The devices 26, 26', ... can also be made of vacuum tuner material deposited on a support The devices of this type can be produced according to a variety of techniques.A first way is the cold rolling of the powders of vacuum tuner material on the metal support, according to a technique well known in the art. the field of powder metallurgy Another way is to atomize a suspension of vacuum tuner particles in a suitable solvent onto the hot maintained metal support, such as described in patent application WO 95/23425, to be referred to for details of this technique. Additionally, the metal support can be covered by particles of vacuum tuning material by the electrophoretic technique; for details of this technique, reference should be made to U.S. Patent 524559. Finally, the deposition of powder of vacuum tuning material on the metal support can be obtained by screen printing technique, as described in the application PCT patent application WO 98/03987. The support can be made of any metal capable of withstanding temperatures of about 600 ° C, which may be necessary for the activation of the vacuum tuner material, and preferably not be ferromagnetic, in order to avoid interference with the magnetic fields sometimes used. in PVD processes. The use of steel alloys or nickel-chromium is preferred. The thickness of the support can vary within a wide range, and generally ranges from 0.1 to 1 mm; outside of mechanical stability, the thickness of the support preferably increases as the lateral dimensions of the vacuum tuning device 26 increase. The thickness of the vacuum tuning material reservoir 29 in the device 26 can vary within a wide range, but, out of the convenience of production and mechanical stability of the deposit, this thickness generally ranges from about 20 to 500 μm. In this case the vacuum tuning devices are mounted on the screens so that the surface of the vacuum tuning material faces the latter. Unlike the aforementioned case, where the vacuum tuner system is formed of sintered bodies, when the vacuum tuner devices are obtained by depositing the vacuum tuner material on a metal support, the system is preferably formed of a relatively small number of such devices, each having a surface similar to that of the screen having them secured to it, so that one, or two at most, of these devices are secured to each screen . The production of devices of this type, having a relatively large surface, is easy and saves time and costs both for manufacturing the vacuum tuning devices and for securing them to the screens. Figure 6 shows a possible mode of vacuum tuner devices obtained by depositing vacuum tuner materials on a metal support. The device 60 is formed of an essentially flat metal support 61 which has deposited on a surface 62 of the same vacuum tuning material 29 (the Figure shows only a partial cover made of vacuum tuning material); the device has a plurality of holes 31, 31 ', ...; the support 61 preferably has distortions, such as, for example, raised edges 63, 63 ', shown in the Figure or similar members, which act as separators between the device and the screen having the device secured thereto. As previously mentioned, the holes 31, 31 ', ... can be regular or not, and can be arranged in the support 61 as a regular network or not, the first way being preferred for easier automated production. A possible way of mounting a screen of a PVD camera and a vacuum tuning device that is part of a system according to the invention is shown in Figure 7, showing a screen 20 having a device secured thereto. 26 simple of type 60; the device 26 can be secured to the screen through suitable mechanical mounting members, such as screw, or through welding points 70, 70 ', ..., at the edge 63 of the vacuum tuning device. Vacuum-tuning devices require an activation for their work, generally consisting of heating, by a variety of means, at temperatures of at least 300 ° C. This operation can be done during the preparatory steps of the working chamber, such as, for example, heating the entire chamber to degas the walls and obtain a better resulting vacuum. Otherwise, the activation of the vacuum tuning device can be obtained during the operations of deposition of material on the available substrates, performed to clean the surface of the target 15, which are generally contaminated before each deposition step; these operations generally result in sufficient chamber heating for activation of the vacuum tuner. By the vacuum tuning system of the invention, another advantage is obtained in the case that the material to be deposited (16) is titanium. Titanium, deposited as thin layers, is well known as a vacuum tuning material. During the deposition of titanium in the physical vapor deposition chambers, some metal is also deposited on the walls of the work area, including the screens. In particular, this thin layer absorbs hydrogen in the working atmosphere, and, due to this absorption, first swells and then releases from the surfaces on which they are in the form of metal microlayers; these could reach the substrate being processed, thus affecting its quality and contributing to the percentage of waste. By contrast, by the system of the invention, hydrogen is preferably absorbed by the vacuum tuning material, thereby overcoming the disadvantage that occurs in the common chambers for physical vapor deposition.

Claims (24)

1. A vacuum tuning system (24) for purifying the gaseous atmosphere of the work area (21) in the physical vapor deposition processes, formed of one or more essentially flat vacuum tuning devices (26, 26 ', .. 35, 40, 60) inserted into said area in an array such that said vacuum tuning devices are essentially parallel and spaced with respect to the screens (20, 20 ', ...) which define the area of work and that space (25) between the vacuum tuner devices and the screens is connected to the work area, said vacuum tuner devices being so that at least the surface (28) facing the screens is made of material of vacuum tuner (29).

2. A vacuum tuner system according to claim 1, wherein the occupation fraction of the surface (27) of the vacuum tuning devices that face the work area varies from 70 to 99% of the surface available.

3. A vacuum tuner system according to claim 2, wherein said occupation fraction is obtained by arranging the vacuum tuner devices in the work area so as not to have contact with each other.

4. A vacuum tuner system according to claim 2, wherein said occupation fraction is obtained by using vacuum tuner devices having a discontinuous surface.

5. A vacuum tuning system according to claim 2, wherein said occupation fraction is obtained by arranging in the work area vacuum tuner devices having a discontinuous surface in order not to have contact with each other.

6. A vacuum tuner system according to claim 2, wherein said occupancy fraction varies from 80 to 95%.

7. A vacuum tuner system according to claim 1, wherein the distance between the vacuum tuner devices and the screens varies from 1 mm to 5 cm.

8. A vacuum tuner system according to claim 1, wherein the vacuum tuner material is selected from the metals Zr, Ti, Nb, Ta, V, the alloys between said metals, the alloys of said metals and one or more metals selected from Cr, Mn, Fe, Co, Ni, Al, Y, La and rare earths, mixtures of said metals and said alloys.

9. A vacuum tuner system according to claim 8, wherein the vacuum tuning material is the alloy having weight composition Zr 84% - Al 16%.

A vacuum tuning system according to claim 8, wherein the vacuum tuning material is the alloy having the weight composition Zr 70% - V 24.6% - Fe 5.4%. eleven .

A system according to claim 8, wherein the vacuum tuning material is a mixture of the alloy having a composition by weight Zr 84% - Al 16% and a metal selected from Zr and Ti.

12. A vacuum tuner system according to claim 8, wherein the vacuum tuner material is a mixture of the alloy having a composition by weight Zr 70% - V 24.6% - Fe 5.4% and a metal selected from Zr and You.

13. A vacuum tuner system according to claim 1, wherein the vacuum tuner devices are made alone of vacuum tuning material (35; 40).

14. A vacuum tuner system according to claim 13, wherein said vacuum tuner bodies are obtained by sintering powder.

15. A vacuum tuner system according to claim 1, wherein the vacuum tuner devices are formed from a reservoir of vacuum tuner material on a support (61) made of a metal capable of withstanding heat treatments up to 600 ° C.

16. A vacuum tuner system according to claim 15, wherein the metal forming the support is not ferromagnetic.

17. A vacuum tuner system according to claim 15, wherein the support is made of steel.

18. A vacuum tuner system according to claim 15, wherein the support is made of a nickel-chromium alloy.

19. A vacuum tuner system according to claim 15, wherein the vacuum tuner material is deposited on the metal support by cold rolling.

20. A vacuum tuner system according to claim 15, wherein the vacuum tuner material is deposited on the metal support by atomization technique. twenty-one .

A vacuum tuner system according to claim 15, wherein the vacuum tuner material is deposited on the metal support by electrophoretic technique.

22. A vacuum tuner system according to claim 15, wherein the vacuum tuner material is deposited on the metal support by screen printing technique.

23. A vacuum tuning system according to claim 15, wherein the support has a thickness ranging from 0.1 to 1 mm.

24. A vacuum tuner system according to claim 15, wherein the reservoir of vacuum tuner material has a thickness ranging from 20 to 500 μm.