KR100523955B1 - Getter system for purifying the working atmosphere in the process of physical vapor deposition - Google Patents

Abstract

A work, formed of at least one getter device in the form of a sintered body of getter powder or a deposit of getter material on a metal support arranged in the working region of the processing chamber for the deposition of a thin layer of metal or ceramic material from a gas or plasma. A getter system for purifying gaseous bodies contained within an area.

Description

Getter system for purifying the working atmosphere in the physical vapor deposition process

The present invention relates to a getter system for purifying a working atmosphere in a physical deposition process.

The process of depositing a thin layer of metal or ceramic material from a suitable gas or plasma is widely used in the art and generally referred to as physical vapor deposition or simply PVD. These processes are used, for example, to deposit multiple layers which are selectively removed later to obtain integrated circuits in the semiconductor art, or to form reflective layers of aluminum in the compact disc industry.

The gas used in all these processes is required to be of high purity. In particular, in semiconductor manufacturing, impurities in the process gas create microflaw in electronic devices, and the smaller the size of the device, the greater the effect of the operational flaw of such a device. Due to the continuing trend of decreasing the average size of these devices, it is necessary to use a purer process gas to reduce the scrap rate.

The use of getter materials in combination with conventional pumps to purify gases upstream for PVD processes is now commonly practiced in the industry. However, purity control of the inlet gas in the production line is insufficient because impurities can enter the working atmosphere due to degassing of the material forming the walls or other parts of the chamber. In particular, certain processes, such as the deposition of aluminum or titanium nitride layers, can cause contaminants. This deposition is accomplished by a technique known as sputtering, in which the flat surface of the target of the material to be deposited is eroded by the impact of heavy atoms of ions (generally Ar + ions) accelerated by a suitable electric field; Particles removed from the target surface are deposited on a substrate of semiconductor material generally disposed parallel to the target surface in the form of a thin film layer. For example, gases in targets mechanically contained within the structure of the material during manufacture are released during the sputtering process, resulting in high concentrations of impurities in the work area. The most common of these impurities are H ₂ O, H ₂ , CO, CO ₂ and CH _4, and their concentration depends on the nature of each process but ranges from about 1 to 100 ppm.

Published patent applications WO 96/13620, WO 96/17171, EP 693626 and WO 97/17542 refer to gas purification with a getter pump arranged inside the PVD chamber. These applications describe getter pumps arranged inside the chamber at a portion remote from the work area. The main advantage of using these pumps in situ is the reduction of dead times required to open the chamber each time, for example to bring the level of impurities below a predetermined value during maintenance work. .

However, these systems do not solve or partially solve the problems caused by impurities in the working area during PVD operations, which target materials on undesirable parts of the chamber, such as supply passages, openings, etc. for connecting the chamber to gas pipes and the like. This is because these areas are formed by a screen which acts to prevent the deposition of metal. These screens greatly reduce the gas transfer between the work area and the rest of the chamber, and have the side-effect of creating two different gas atmospheres inside the process chamber, thereby working with the in situ getter pump described above. Sorption of impurities in the region is negligible. Therefore, the problem of effective purification of the working atmosphere during the PVD process and the contamination of the layer deposited on the support by these processes have not yet been solved.

It is an object of the present invention to provide a getter system for purifying a gas atmosphere in a work area in a physical deposition process.

The object is achieved according to the invention by a getter system formed of at least one planar getter device inserted inside a working area of a process chamber for physical vapor deposition, in which arrangement the getter device is directed to a screen forming the working area. Spaced apart in parallel, the space between the getter device and the screen is connected to a work area, wherein the getter device is such that at least the surface facing the screen is made of getter material.

The invention will now be described with reference to the drawings.

Referring to FIG. 1, a process chamber for manufacturing an integrated device is shown schematically. The chamber 10 is formed of a housing 11 which forms a space 12 isolated from the atmosphere. The chamber is connected to a pumping system for evacuation, generally indicated at 13, and to a supply line for at least one process gas, generally indicated at 14. Inside the chamber 10 is a target 15 which is generally shaped like a disk or a short cylinder and made of a material 16 to be deposited as a thin film layer; A support 17 for supporting a housing for a substrate 19 of semiconductor material (typically silicon) on which the thin film material 16 is deposited; Finally, there are screens 20, 20 ', ... (only two are shown in the figure). The screens 20, 20 ′,... Are arranged in a space 12 with two areas, namely the work area 21 and the area 22 having an auxiliary structure of the PVD process, such as an electrical connection or an inlet to a gas supply line. Divide by; These areas 21 and 22 contact each other only through small conductance 23 at the edge of the screen. There are various modifications to the simple design described above. For example, the work area 21 may be square, rectangular or cylindrical; In either case, the screen is generally planar and inserted inside the chamber 10 in a polygonal configuration that is most suitable for forming the desired geometric shape within the work area. The target 15 may be made of a forerunner of the material 16 to be deposited on the substrate 19, or in some cases to allow continuous deposition of layers of different materials without opening the chamber. It can be part of a multiple target system used. The support 17 can generally be moved vertically to move the substrate 19 to the working position, while the housing 19 generally holds the substrate 19 at the best temperature to obtain a thin film layer with good homogeneity. Heated to maintain; This temperature depends on the material 16 but is generally in the range of about 100 to 500 ° C.

The prior art getter pumps are arranged in various positions inside the chamber 10, and in any case are always arranged in the area 22, and therefore they are due to the small induction between the working areas 21, 22. It is practically isolated from the gas atmosphere.

In contrast, according to the present invention, the getter system is arranged inside the region 21 and is therefore in an effective position to adsorb the impurities within this region.

In particular, since the getter system according to the present invention is mainly formed of a flat getter device which is fixed to the screen, these getter devices are almost parallel to the screen, and there is a space between the screen and the getter device, which is the working area 21. ); In addition, the getter device must be secured to the screen such that at least the surface facing the screen is made of getter material.

2 shows an outline of the getter system configuration of the present invention inside a PVD process chamber. The getter system 24 is mainly parallel to the screens 20, 20 ′,..... And forms a space 25 between the screen and the system 24. System 24 is formed of getter devices 26, 26 ',...; The figure does not show a means for securing the devices 26, 26 ′,... To the screen 20, 20 ′,...... Which means are used, as described later. This is because it depends on the specific form of the getter device. The getter system 24 has a surface 27 facing the work area 21 and a surface 28 facing the screens 20, 20 ′,... At least surface 28 should be made of getter material 29. System 24 may be disposed around the work area to sweep at an angle less than 360 degrees, but suitably surrounds the work area, thus increasing the available surface of the getter material and increasing the efficiency of impurity adsorption . As mentioned above, whatever the geometry of the working area, the screen is generally flat, and the getter devices 26, 26 '... Which form the system according to the invention are likewise flat. If the getter system is to be cleaned at an angle less than 360 degrees around the work area 21, it may consist of only a single getter device. However, as described above, when the getter system suitably cleans the work area around a 360 degree angle, it is formed of several getter devices, and is generally formed of at least more getter devices than the number of screens.

The space 25 should be connected to the area 21. The connection conditions between the space 25 and the area 21 are many ways, for example between the area 21 and the space 25 in the areas 30, 30 ′ where the surface 27 is continuous and shown in FIG. 2. It is made by a getter device with an induction part of However, the required conditions are preferably met by the getter devices 26, 26 '... formed or shaped such that the surface 27 is discontinuous; In particular, the best efficiency for removing impurities from region 21 is that the sum of the effective surfaces 27, i.e., the surfaces facing region 21 for all getter devices, is 70 to 99% of the available surface of the continuous getter system. Suitably at a fraction in the range from 80 to 95%. The discontinuity of the surface 27 may be in the form of voids between the adjacent devices or through holes in the devices 26, 26 ′; The possibilities for both of these are shown in the figures, and the discontinuities are indicated by the reference numerals 31, 31 '. In both cases, discontinuities can have a regular or irregular shape and can be regularly or irregularly placed on the available surface; For example, in the case of holes on the surface of a single getter device, they may be square or round or irregular in shape, and may be arranged in a networked or disordered manner on the surface of the getter device, between adjacent getter devices. In the case of space, the shape and configuration of the discontinuity will depend on whether the devices 26, 26 '... are regularly arranged on the available surface. In general, for both single getter devices and adjacent devices, discontinuities of regular shape and configuration are suitable, which is best suited for automated manufacture of getter system 24 and between the effective and available surfaces for system 24. This is because it allows easier control of the aforementioned conditions for the ratio. Clearly a mixed structure is possible, in which case a single getter device has holes and adjacent getter devices are spaced apart from each other.

The distance between the getter system 24 and the screens 20. 20 ′,... S depends mainly on the overall size of the area 21 and the distance between adjacent getter devices and / or the size of the holes on the device. In general, the distance between the getter system and the screen ranges from 1 mm to 5 cm; Within these ranges the distance is generally less in a small size PVD chamber to prevent adverse effects of the getter system on processes occurring in the work area; Moreover, the distance increases as the distance between adjacent getter devices and / or the size of the holes on the device increases.

A wide range of getter materials that can be used to make devices 26, 26 ', .... are metals such as Zr, Ti, Nb, Ta, V, alloys of these metals, or Cr, Mn, Fe with these metals. Alloys of one or more elements selected from among Co, Ni, Al, Y, La and rare earth metals, for example binary alloys of Ti-V, Zr-V, Zr-Fe and Zr-Ni or Zr-Mn-Fe Or Zr-V-Fe ternary alloys, or mixtures of the aforementioned metals and alloys. The most commonly used getter materials are alloys having a composition of Zr 84% by weight to Al 16% by weight, sold under the trade name St 101 (registered trademark) manufactured by Company Sas Getters (Milan, Italy); An alloy having a composition of Zr 70 wt%-V 24.6 wt%-Fe 5.4 wt%, sold by the company Sas Getters under the trade name St 707; Mechanical mixtures of these two alloys with Zr or Ti; These mixtures are preferred because of their good mechanical properties, especially with regard to particle loss.

The getter devices 26, 26 ′,... May be bodies made of only the getter material and obtained by powder sintering, or may be made of the getter material deposited on the metal support according to various techniques.

The manufacture of sintered bodies from powders is known in the field of powder metallurgy and generally comprises compacting the powder in a suitable mold and heating the coagulated powder until a partial melting of the surface of the powder particles is obtained. . Modifications to the method are described in US Pat. Nos. 5,324,172 and EP-A-719609, and in patent application EP-A-765012, in the name of the applicant, in order to obtain a special structure, for example a body with high porosity. It is. 3 and 4 show this type of getter device. The device 35 of FIG. 3 is rectangular in shape and has through-holes 36, 36 ′ provided for the use of members such as screws and bolts for securing the device and the screen at a distance from their ends; Other means for securing the device to the screen, for example, a suitable spacer that can be secured to the screen, and a metal member incorporating a frame therein for holding the getter body; The device 40 of FIG. 4 is mainly square in shape and has a series of through-holes 31, 31 ′.... Which allow for easy connection between the work area 21 and the space 25 as described above. . During the PVD process, the surface facing the area 21 is covered by the material 16 to be deposited as a thin film layer on the substrate 19, while the surface 28 is activated to adsorb impurities.

Because planar sintered bodies with lateral dimensions much larger than the thickness are complicated to manufacture and have low mechanical strength, when using such bodies for the getter system of the present invention, the getter system is preferably formed with a large number of getter devices. Each of these devices has a surface that is significantly smaller than the screen on which the device is fixed. This kind of configuration is shown in FIG. 5, where a number of devices 26, 26 ′, 26 ''... Some are shown; The devices 26,... Are fixed to the screen via suitable mounting members 37, 37 ′ and also act as spacers.

Getter devices 26, 26 ′,... May be made of getter material deposited on a metal support. Devices of this type can be manufactured according to various techniques. The first method is cold lamination of getter material powder onto a metal support according to techniques known in the powder metallurgy art. Another method is to spray a suspension of getter particles on a metal support kept in a high temperature in a suitable solvent, such as the technique known in the patent application WO 95/23425, which is referred to for the detailed description of the present technology. Moreover, the metal support can be covered with getter material particles by electrophoretic technique; For a detailed description of this technique, see US Pat. No. 5,242,559. Finally, the deposition of the getter material powder on the metal support can be obtained by a screen printing technique, as disclosed in PCT patent publication WO 98/03987. The support is required for the activation of the getter material and may be suitably made of any metal that can withstand temperatures of about 600 ° C., not ferromagnetic, to avoid interference with the magnetic field that is sometimes used in PVD processes. It is suitable to use steel or nickel-chromium alloys. The thickness of the support can vary widely and is generally in the range of 0.1 to 1 mm; Due to the mechanical stability, the thickness of the support suitably increases with increasing side dimensions of the getter device 26. The thickness of the getter material deposits 29 in the device 26 can vary over a wide range, but due to the convenience and mechanical stability of the manufacture of the deposits, this thickness is generally in the range of 20 to 500 μm. In this case the getter device is mounted on the screen such that the surface of the getter device faces the screen. In contrast to the above case where the getter system is formed of a sintered body, when the getter device is obtained by depositing getter material on a metal support, the system suitably forms the system with a relatively small number of devices, each of which is described above. Since the device has a surface similar to that of a fixed screen, at most one or two of these devices are fixed to each screen. Fabrication of this type of device with a fairly large surface is easy and allows to save both time and money when manufacturing the getter device and securing them to the screen.

6 illustrates a possible embodiment of a getter device obtained by depositing getter material on a metal support. The device 60 is basically formed of a planar metal support 61 having a getter material 29 deposited on the surface 62 of the device (the figure only shows a partial covering formed of the getter material); The device has a plurality of holes 31, 31 ′,... The support 61 suitably has warps, such as raised edges 63, 63 'or similar members, shown in the figure, which act as spacers between the device and the screen on which the device is fixed. As described above, the holes 31, 31 ′,... May be of regular or irregular shape, may be arranged on the support 61 as a regular network or an irregular network, and the first It is suitable for automated manufacturing where it is easier. A possible method of assembling the screen of the PVD chamber and the getter device which is part of the system according to the invention is shown in FIG. 7, which shows a screen 20 in which a single device 26 (shaped 60) is fixed. ; The device 26 may be secured to the screen on the edge 63 of the getter device via a suitable mechanical mounting member such as a screw or welding spots 70, 70 ′,...

The getter device generally requires an activation operation consisting of heating to a temperature of at least 300 ° C. by various means. This can be done during the preliminary stage of the chamber operation, for example, heating the entire chamber to degas the wall and obtain a better vacuum. Otherwise, getter device activation may be obtained during material deposition operations on the treatable substrate, and may be performed to clean the surface of the target 15, which is generally contaminated before every deposition step; These operations generally result in heating of the chamber sufficient for getter activation.

With the getter system of the present invention, another advantage is obtained when the material 16 to be deposited is titanium. Titanium deposited as a thin film layer is well known as a getter material. During titanium deposition in the chamber for physical vapor deposition, certain metals may also be deposited on the walls of the work area, including screens. In particular, these thin film layers adsorb hydrogen in the working atmosphere, and by this adsorption they first expand to the surface in the form of metal microlayers and then fall off; They reach the substrate to be processed, which affects the quality of the substrate and contributes to increasing the scrap rate. In contrast, with the system of the present invention, hydrogen is suitably adsorbed by the getter material and thus overcomes the drawbacks that occur in commercial chambers of physical vapor deposition.

1 is a schematic diagram of a process chamber for physical vapor deposition.

2 is a contour view of the position of the getter system inside of the process chamber of FIG.

3 and 4 are perspective views of embodiments of a getter device of the first type that can be used in the system of the present invention;

5 is a perspective view of a possible getter system of the present invention formed with the apparatus of FIG.

6 is a perspective view of an alternative embodiment of a getter device of the second type that may be used in the system of the present invention.

7 is a perspective view of another possible getter system of the present invention formed with the apparatus of FIG.

    Explanation of symbols on main parts of drawing

15 target 17 metal support

20, 20 '....: Screen 21, 22: Work Area

26, 26 '....: Getter Device

Claims (3)

Getter system formed of one or more basically planar getter devices 26, 26 ', ...; 35; 40; 60 inserted inside the area to purify the gaseous atmosphere of the work area 21 in a physical deposition process. As 24, The getter devices are basically parallel and spaced apart from the screens 20, 20 ′,... Which form the working area, and the space 25 between the getter device and the screen is connected to the working area. And a getter system wherein at least the surface (28) of the getter device facing the screen is made of getter material (29). 2. The getter system of claim 1, wherein the getter device is made only of getter material (35; 40). 2. The getter system of claim 1, wherein the getter device is formed of a getter material deposit on a support (61) made of metal capable of withstanding heat treatment up to 600 ° C.