Patent Application
20150034481
The present invention relates, in a vacuum device configured to perform a film forming process on a processing target substrate under vacuum, to a fastening member for attaching a member to the inner wall of the chamber of the vacuum device and to the vacuum device.
Conventionally, film forming devices have been used to perform film forming processes on processing target substrates such as silicon wafers, liquid crystal display substrates, optical discs, and MiniDiscs in various types of manufacturing processes such as semiconductor manufacturing processes, liquid crystal display panel manufacturing processes, and disc manufacturing processes.
Here, since atoms and molecules emitted from the targets 405, 406 fly in random directions, a film is deposited on unwanted areas such as the inner wall of the vacuum chamber 401. As the process is repeated, the deposited film accumulates and is eventually separated, thereby adversely affecting the quality of the film formation. This creates a need for removal via regular maintenance.
For this reason, film forming devices usually use a part called a shield to define a film forming space from each target 405, 406 to a substrate 407, and this shield is regularly replaced to achieve a stable film forming quality. The film forming device in
For the fixing of these shield and shutter parts, a structure in which they are bolted from inside the film forming space is sometimes used in light of ease in detachment and replacement.
In general, stainless steel is often employed as the material of the bolt used in such a structure for its good commercial availability and good corrosion resistance. However, among metals, stainless steel has low thermal conductivity and a large coefficient of thermal expansion. Thus, a phenomenon called galling is likely to occur in which external and internal threads adhere and immovably fixed to each other due to frictional heat generated in the threads during fastening. When this galling phenomenon occurs, fastening with the same torque results in greater friction between the threaded portions, which in turn causes a problem of a greater risk of particle generation.
As a technique to prevent galling of threaded portions as described above, the technique of coating the threaded portions with lubricant that reduces the coefficient of friction has been widely used. Here, in a case of coating grease. Teflon (registered trademark), or the like inside a vacuum device, there is a risk that the coating layer may be degassed and contaminate the film forming environment. For this reason, coating of a soft metal, such as silver, which has a lubricating function and also produces only a small amount of volatilized gas under vacuum has often been used.
By applying solid lubricating means such as sliver plating to the threaded portions, and further by giving the bolt head section greater surface roughness than its base material by a blasting process or the like, a shield fastening structure suppressing particle generation can be obtained.
In the above-described shield fastening structure, particle generation does not occur when the shield is fastened with a new bolt and a new threaded hole. However, as a bolt that has once been fastened is removed for replacement of the shield, the silver plating is easily separated. Thus, as the shield replacement operation is repeated, the separated silver accumulates in the internally threaded portion or floats in the film forming space and eventually causes contamination such as adhesion to the processing target object.
Meanwhile, Patent Document 3 discloses a shield fastening structure in which a shield and an entire bolt are coated with molybdenum.
Patent Document 1: Japanese Patent Application Laid-Open No. Hei 04-202768
Patent Document 2: Japanese Patent Application Laid-Open No. Hei 11-092913
Patent Document 3: Japanese Patent Application Laid-Open No. Hei 08-041637
However, there is also a problem in the shield fastening structure in Patent Document 3 in that the coating film itself has a risk of becoming a source of contamination as the shield replacement operation is repeated. There is another problem in the shield fastening structure in Patent Document 3 in that although the film removal from the head section of the bolt 612 can be done more easily, there is, at the same time, a greater risk of the deposited film falling from the head section of the bolt 612 into the sputtering device while the sputtering device is in use. However, no solution to these problems has been known.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a fastening member which involves only a low risk of contamination even after repeatedly performing a detachment operation, and to provide a vacuum device including the fastening member.
For achieving the above-mentioned object; one aspect of the present invention provides a fastening member for attaching a member to an inner wall of a chamber of a vacuum device, comprising: a head section including a head-upper-face portion, a seating face portion opposed to the head-upper-face portion, and a head-side-face portion forming a side wall between the head-upper-face portion and the seating face portion; and a shaft section provided on the seating face portion side of the head section and including a threaded portion on an end portion thereof on the opposite side from the head section, wherein the threaded portion is given higher hardness than at least those of other portions of the fastening member, and when the member is attached to the inner wall of the chamber with the fastening member, the threaded portion is threadedly engaged with an internally threaded portion provided in the inner wall of the chamber, and the seating face portion presses the member against the inner wall of the chamber.
In the fastening member according to the present invention, the threaded portion of the fastening member is given higher hardness than at least those of other portions of the fastening member. Thus, when the member is attached to the inner wall of the chamber with the fastening member, it is possible to suppress wear resulting from friction between the threaded portion and the internally threaded portion. At the same time, the threaded portion given the higher hardness has a lower coefficient of thermal expansion than that of the base material of the fastening member, thereby suppressing the thermal expansion itself. Accordingly, it is possible to reduce generation of particles from the threaded portion resulting from detachment and attachment operations of the fastening member.
BRIEF DESCRIPTION OF DRAWINGS
Hereinbelow, the contents of the present invention will be described in detail with reference to drawings.
Vacuum devices to which the fastening member of the present invention is applicable are not limited to the one described in this embodiment; physical vapor deposition device, chemical vapor deposition (CVD) devices, atomic layer deposition (ALD) devices, and the like are available.
Unillustrated gas introducing means for supplying a sputtering gas such for example as argon is connected to the vacuum chamber 1. By evacuating the vacuum chamber 1 via the evacuating means 2 while introducing the gas, and also by applying power from the DC power source such that the voltage at the target 6 will be negative, the magnet causes magnetron discharge. The magnetron discharge turns the sputtering gas into plasma in the vicinity of the target 6, and positive ions in this plasma are accelerated by and collide with the target 6 at the negative voltage. By the collision of the positive ions, atoms, molecules, and the like are emitted from the target 6, and the metal thus produced reaches the front face of the substrate 3 facing it. As a result, a desired film is deposited. Further, if the gas introducing means introduces the sputtering gas with oxygen, nitrogen, or the like mixed therein, so-called reactive sputtering can be performed which allows deposition of a metal nitride film or a metal oxide film.
In the device in
Meanwhile, since the atoms and molecules emitted from each target 6 fly in random directions, a film is deposited on unwanted areas such as the inner wall of the vacuum chamber 1. As the process is repeated, the deposited film accumulates and is eventually separated, thereby adversely affecting the quality of the film formation. This creates a need for removal via regular maintenance.
For this reason, film forming devices usually use a part called a shield to define a film forming space from each target to a processing target object, and this shield is regularly replaced to achieve a stable film forming quality. In
The fastening member illustrated in
A fixing part 103 including an internally threaded hole 115 is provided on the inner wall of the chamber 1 at a position at which a fixing target member 102 should be fixed. An internally threaded portion 105a threadedly engageable with the threaded portion 106a is formed on the inner wall face of the internally threaded hole 115. To attach the fixing target member 102 to the fixing part 103 with the fastening member, the threaded portion 106a is threadedly engaged with the internally threaded portion 105a, and they are fixed such that the seating face portion 111 presses the fixing target member 102 against the fixing part 103.
In this embodiment, the fixing target member 102 is a shield part 102 provided inside the vacuum chamber 1 illustrated in
The fastening member is, for example, a hexagonal head bolt made of a stainless steel SUS316L with the threaded portion 106a measuring 5 mm in outer diameter. By being connected to the internally threaded portion 105a provided in the fixing part 103, which is likewise made of SUS316L, via the through-hole (the first hole portion 113, the second hole portion 114) provided in the shield part 102, the hexagonal head bolt applies force in a compressing direction to and thus fastens the shield part 102. To fasten or detach the shield part 102, such an operation is performed by connecting, for example, a hexagonal wrench to the head-side-face portion 108. Note that the shield part 102 is attached to the inner wall of the chamber 1 with the fixing part 103 therebetween in
Here, the internally threaded hole 115 provided in the fixing part 103 which fastens to the shield part 102 may not be in a concave shape as illustrated in
As the surface hardening process, formation of a hardened layer on the stainless steel with a gradient by a carbon doping process (or a so-called carburizing process) may be employed. In this way, it is possible to perform a surface hardening process without separation even after multiple fastening and detaching operations. In this embodiment, the carburizing processing is performed on the head-side-face portion 108, the threaded portion 106a, and the seating face portion 111 of the bolt head section of the fastening member, as well as on the internally threaded portion 105a of the fixing part 103. As a result of the doping of carbon with a concentration gradient changing in the depth direction, the Vickers hardness (hereinafter referred to as HV) of the surface is improved to, for example, about a HV of 700 as compared to the HV of the base material, or 3US316L, which is 200.
As the surface hardening process, a nitriding process or an anti-wear coating process can be used besides the carburizing process used in this embodiment. The coating process is a process in which a film made of a different material than the base material is formed on the surface; publicly known ion plating, sputtering, or the like can be used, and various types of films such as those of TiN are available as the coating film.
Note, however, that the anti-wear coating mentioned here refers to one that involves formation of a strong film on a coated surface to improve the hardness, and not to those that involve adhesion of part of a coated film to the counterpart (adhesion of a coated film to an internally threaded portion in a case where its externally threaded portion is coated therewith) as in a case of using a so-called solid lubricant such as the molybdenum coating used in Patent Document 3, silver platings or fluorine coating. Such anti-wear coating is less likely to become a source of contamination and is therefore preferable.
As the carburizing process, for example, a publicly known plasma carburizing process is used. In this embodiment, during the carburizing process, the process is performed with the head-upper-face portion 107 of the head section 101 set in close contact with a stainless part 150 so as to be masked as illustrated in
With the hardness of the threaded portion 106a, the head-side-face portion 108, the seating face portion 111, and the internally threaded portion 105a improved to higher hardness, it is possible to suppress wear resulting from friction between members when the shield part 102 and the fixing part 103 are attached with the fastening member. Moreover, by the improvement to higher hardness, the coefficient of thermal expansion decreases below that of the base material. Thus, the thermal expansion itself is suppressed as well. Accordingly, it is possible to reduce generation of particles resulting from detachment and attachment operations of the fastening member.
After the surface hardening process, a roughening process such as alumina blasting is performed on the head-upper-face portion 107 of the head section 101 so that its surface roughness can be equal to or greater than the surface roughness of the seating face portion 111, e.g. an arithmetical mean roughness (Ra) of 3.5 μm and a ten-point mean roughness (Pz) of 20 μm. Performing, on the head-upper-face portion 107, a surface roughening process which gives surface roughness equal to or greater than a ten-point mean roughness (Rz) of 10 μm or greater as described above brings about an advantageous effect of making the deposited film on the head-upper-face portion 107 separated less easily therefrom, and thereby improving the reliability of the device. In general, the higher the hardness of a processing target surface, the less efficient its surface roughening process becomes. However, in this embodiment, as illustrated in
As the blasting process, various blasting methods such as one using glass beads, silicon carbide, dry ice, or the like are available besides alumina blasting.
If the surface hardening process is performed after the surface roughening process, the surface roughness formed by the surface roughening process would be decreased by the surface hardening process. However, in this embodiment, the surface roughening process (blasting process) is performed after the surface hardening process, which brings about an advantageous effect of making the surface roughness formed by the surface roughening process decrease less easily. Moreover, since the surface roughening process is performed by using a publicly known blasting process, the necessary surface roughness can be obtained at a low cost. Further, since the head-upper-face portion 107 is masked during the surface hardening process, the surface roughness obtained from the surface roughening process is increased, which brings about an advantageous effect of reducing the generation of particles.
Here, it is more preferable to also thermally spray a metal such as aluminum or titanium after the blasting process, since doing so can provide even greater surface roughness and make the deposited film less easily separated from the film forming space. For example, a surface with a ten-point mean roughness (Rz) of approximately 50 μm can be obtained by adhering pure aluminum to a thickness of about 100 μm by plasma spraying.
As the thermal spraying process, various methods such as arc spraying are available besides plasma spraying.
It is preferable to form a path for cooling with cooling water as cooling means in the vacuum chamber 1 in the vicinity of the internally threaded portion 105a. In this way, it is possible to reduce friction between the threaded portion 106a and the internally threaded portion 105a resulting from their thermal expansion, and therefore suppress generation of particles. Meanwhile, surface hardening processes are generally known to be affected by high temperature environments. For example, it is known that in a case of a carburizing process on a base material of stainless steel (e.g. SUS316), the composition of the surface phase changes at or above 400° C. and the hardness drops. Further, in a case of a coating process with TiN or the like, the risk of separation increases under a high temperature environment due to the difference in coefficient of thermal expansion from the base material. Thus, by providing the cooling means, the internally threaded portion 105a can be maintained at low temperatures, thereby making it possible to maintain the hardness of the surface of the fastening member and suppress generation of particles.
As described above, the front face 110 of the shield part 102 is positioned higher than the head-side-face portion 108 of the fastening member. Thus, deposition of a film onto the head-side-face portion 108 can be suppressed. While the shape and size of the opening of the through-hole 105 at the front face 110 of the shield part 102 may be any shape and size, a circular opening measuring 13 mm in diameter is provided here for a bolt with a hexagonal head measuring 4.6 mm in length on each side, as illustrated in
With the configuration according to this embodiment, it is possible to reduce powder resulting from wear of each of the portions that come into contact with a tool (such as the head-side-face portion 108), the seating face portion 111, the head-upper-face portion 107, the threaded portion 106a, and the internally threaded portion 105a and also to reduce falling of the deposited film therefrom even when a replacement operation of the shield part 102 is repeatedly performed. Accordingly, the reliability of the device can be improved. Further, since the hardened layer formed on the surface of the fastening member wears only to a small extent even after repeated use, the fastening member can be used repeatedly by removing the film deposited on the head-upper-face portion 107. This is effective in reducing the running cost of the device.
In this embodiment, the structure in which the shield part 102 (the shield 5, 9) is fastened with the fastening member is described. However, the same fastening structure can be used to fasten other elements (such as the shutter 10) in the chamber 1 with the fastening member.
The fastening member according to the present invention is not limited to the example described above. The shape of the bolt head, the length and pitch of the threaded portion, and other features can be any shape, length, pitch, etc.
In
In general, the surface layer of stainless steel hardened by coating is low in coefficient of thermal expansion, which leads to cases where cracking or the like occurs under high temperature environments due to the difference in coefficient of thermal expansion from the base material. In addition, for stainless steel hardened by a carburizing process, there are cases where elimination of carbon occurs or the metallic composition of the stainless steel changes under high temperature environments, thereby causing embrittlement. Thus, by employing the configuration illustrated in
The modes of the present invention are not limited to the above embodiments, but are freely changeable within the scope of the gist of the invention. For example, the shape of the bolt is not limited to the hexagonal shape illustrated in the embodiments, but may be an octagonal shape, a quadrangle shape, or some other shape. Also, the bolt may be provided with a gas evacuating hole for evacuating air between the internally threaded portion and the externally threaded portion. Further, as for the material of the bolt, a material such as titanium or aluminum can be employed. Furthermore, the internally threaded portion may be one with a helical coil insert or the like inserted therein, or one provided with the above-mentioned gas evacuating hole.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-057301 | Mar 2012 | JP | national |
This application is a continuation application of International Application No. PCT/JP2012/005778, filed Sep. 12, 2012, which claims the benefit of Japanese Patent Application No. 2012-057301, filed Mar. 14, 2012. The contents of the aforementioned applications are incorporated herein by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2012/005778 | Sep 2012 | US |
| Child | 14481978 | US |
