Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1999-09-22
2002-09-03
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S307700, C428S701000, C428S702000, C428S704000, C428S698000, C428S472000, C428S469000, C428S446000, C428S472200, C428S697000, C428S699000, C428S212000
Reexamination Certificate
active
06444304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to aluminum (hereinafter simply referred to Al) alloy excellent in anti-corrosiveness to gas and plasma and particularly, to Al alloy suitable for a structural material to build an apparatus, in which gas or plasma including a corrosive component and an element is used, such as a production apparatus for semiconductor or liquid crystal.
2. Prior Art
A production apparatus for semiconductor or liquid crystal such as a chemical or physical vapor deposition apparatus, that is CVD or PVD, or a dry etching apparatus is constructed of a heater block, a chamber, liner, a vacuum chuck, an electrostatic chuck, a clamper, bellows, a bellows cover, a susceptor, a gas diffusion plate, and an electrode etc. as main constituents. In the interior of such a production apparatus for semiconductor or liquid crystal, since a corrosive gas, as reaction gas, including a halogen element such as Cl, F, Br and/or the like, and/or elements such as O,N, H, B, S, C and/or the like is introduced, the constituent members are required to have anti-corrosiveness to the corrosive gas. Furthermore, the main constituent members are necessary to have anti-corrosiveness to plasma since halogen containing plasma is also generated in the interior of the production apparatus in addition to presence of the corrosive gas.
Conventionally stainless steel has been used for a structural material of such main constituent members. Under recent demands for high efficiency and light weight of production apparatuses for semiconductor and liquid crystal, however, there has been pointed out following problems in constituent members made from stainless steel: insufficient in thermal conductivity, resulting in slow start-up in operation; heavy in its size, causing the apparatuses to be heavy as a whole. Besides, there have been occurred another problem since heavy metals such as Ni, Cr and the like included in stainless steel have a chance to be released to an environmental atmosphere so as to work as a contaminant source and thereby, deteriorate qualities of a semiconductor product and a liquid crystal product.
For the reason, aluminum alloy light in weight and high thermal conductivity has rapidly been increased in use, substituting stainless steel. Among various kinds of aluminum alloys, for example, JIS 3003 Al alloy including Mn: 1.0 to 1.5% , Cu: 0.05 to 0.20% and the like; JIS 5052 Al alloy including Mg: 2.2 to 2.8%, Cr.: 0.15 to 0.35% and the like; JIS 6061 Al alloy including Cu: 0.15 to 0.40%, Mg: 0.8 to 1.2%, Cr: 0.04 to 0.35% and the like are generally used. However, surfaces of such Al alloys are not good in resistance to corrosion caused by the above described corrosive gases and plasmas. Accordingly, it is indispensable to improve anti-corrosiveness of the Al alloys to the gases and plasmas in order for the Al alloys to be adopted as structural material of production apparatuses for semiconductor and liquid crystal. In order to improve the anti-corrosiveness, some treatment on an Al alloy surface is the most effective means.
Therefore, a technique has been proposed in the publication of Examined Japanese Patent Application No. Hei 5-53870, in which an anodic oxidation coating of A1203 excellent in anti-corrosiveness is formed on a surface of the above described Al alloys in order to increase anti-corrosiveness to the gas and plasma of the main constituent members of a vacuum chamber and the like. However, the anodic oxidation coating does not always satisfy requirements for anti-corrosiveness in all kinds of environments in which the main constituent members of a production apparatus for semiconductor are placed since a film quality of the anodic oxidation coating shows a largely different degree of anti-corrosiveness to gas or plasma according to environmental conditions.
For such a reason, there have been proposed various! methods to further improve a quality of an anodic oxidation coating in order to increase anti-corrosiveness of such Al alloys as materials of constituent members used in a semiconductor production apparatus. For example, in the publication of Unexamined Japanese Patent Application No. Hei 8-144088, a proposal is such that in formation of an anodic oxidation coating, an initial voltage for anodic oxidation is higher than a final voltage. Further, a proposal has been made in the Unexamined Japanese Patent Application No. Hei 8-144089, in which anodic oxidation is performed in a solution including a phosphate ion and a sulfate ion and a total opening area of pores on an anodic oxidation coating surface is adjusted in a specific range. Still further, other proposals appear in the publications in the Unexamined Japanese Patent Application Nos. Hei 8-260195 and Hei 8-260196, which disclose techniques in which a porous anodic oxidation coating is first formed and then, a coating by non-porous anodic oxidation is overlapped.
Any of such conventional techniques relating to anodic oxidation, as shown in
FIG. 1
, has a fundamental feature that recesses each called a pore 3 are started to be formed on a surface of a base material Al alloy 1 on start of electrolysis, continuing to be formed in progress of the oxidation and thereby, there is formed an anodic oxidation coating 6 comprising a porous layer 4 constructed of cells 2 that grows along the depth direction of the Al alloy 1 and a barrier layer 5. Since the barrier layer 5 has no gas permeability, gas or plasma is prevented from being put into contact with Al alloy. In the publication of Unexamined Japanese Patent Application No. Hei 8-193295 or the like, in order to further increase anti-corrosiveness to a plasma of such double-structured anodic oxidation coating, diameters of pores and cells on the surface side of the porous layer 4 have been proposed so as to be formed as small as possible.
An anodic oxidation coating such that the coating is constructed of the porous layer and barrier layer and diameters of pores and cells on the surface side of the porous layer 4 are formed as small as possible is sure to be excellent in anti-corrosiveness to gas and plasma. However, recent production conditions for semiconductor and liquid crystal have been very severe corresponding to a recent trend toward high efficiency and a large-size scale and gas and plasma related conditions are also severer due to transition toward a high concentration, a high density and high temperature. Accordingly, in recent years, structural materials of a reaction chamber and those of internal constituent members thereof have been required to possess anti-corrosiveness to the increasingly more severe corrosive gases and plasmas including halogen elements such as Cl, F, Br and the like, and elements such as O, N, H, B, S, C and the like, singly or in combination.
For example, evaluation of anti-corrosiveness to a halogen gas and a plasma appeared in the publication of the Unexamined Japanese Patent Application No. Hei 8-193295 is such as, for anti-corrosiveness to halogen gas, no corrosion under test conditions of 300° C.×4 hr in 5% Cl
2
—Ar and for anti-corrosiveness to plasma, 2 &mgr;m or less in etching depth under test conditions of Cl
2
plasma exposure for 90 min. On the other hand, anti-corrosiveness criteria required for structural materials of production apparatuses for semiconductor and liquid crystal with high efficiency are such as, for anti-corrosiveness to halogen, no corrosion after two time repetition of exposure to 5% Cl
2
containing Ar gas at 400° C. for 60 min and in addition, adhesiveness with no separation of a ceramic coating from an anodic oxidation coating in a tape separation test on the same sample. Further, for anti-corrosiveness to plasma, 1 &mgr;m or less in etching depth after repetition of four time of exposure to Cl
2
plasma for 60 min and to CF
4
plasma for 30 min combined. An anodic oxidation coating obtained only by the above described treatment does not meet such severer requirements for anti-corrosiveness to the gases and plasmas.
On the other hand
Hayashi Koichi
Hisamoto Jun
Shige Hiroo
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd).
Morris Terrel
Vo Hai
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