Clean aluminum alloy for semiconductor processing equipment

Details Clean aluminum alloy for semiconductor processing equipment Clean aluminum alloy for semiconductor processing equipment

2002-05-28

2003-05-20

Koehler, Robert R. (Department: 1775)

Stock material or miscellaneous articles

Composite

Of metal

C205S324000, C205S325000, C428S629000, C428S632000, C428S310500, C428S318400, C428S323000, C428S328000, C428S330000, C428S332000, C428S334000, C428S697000, C428S702000

Reexamination Certificate

active

06565984

ABSTRACT:

FIELD OF THE INVENTION
In general, the present invention relates to a composition of an aluminum alloy used in the fabrication of semiconductor processing apparatus. In particular, the invention relates to a structure comprising a clean aluminum alloy which is particularly advantageous when used to fabricate semiconductor processing chamber components.
BRIEF DESCRIPTION OF THE BACKGROUND ART
Semiconductor processing involves a number of different chemical and physical processes whereby minute integrated circuits are created on a substrate. Layers of materials which make up the integrated circuit are created by chemical vapor deposition, physical vapor deposition, and epitaxial growth, for example. Some of the layers of material are patterned using photoresist masks and wet and dry etching techniques. Patterns are created within layers by the implantation of dopants at a particular locations. The substrate upon which the integrated circuit is created may be silicon, gallium arsenide, glass, or any other appropriate material.
Many of the semiconductor processes used to produce integrated circuits employ halogen or halogen-containing gases or plasmas. Some processes use halogen-containing liquids. In addition, since the processes used to create the integrated circuits leave contaminant deposits on the surfaces of the processing apparatus, such deposits are commonly removed using plasma cleaning techniques which employ at least one halogen-containing gas. The cleaning procedure may include a wet wipe with deionized water, followed by a wipe with ispropyl alcohol.
Aluminum has been widely used as a construction material for semiconductor fabrication equipment, at times because of its conductive properties, and generally because of its ease in fabrication and its availability at a reasonable price. However, aluminum is susceptible to reaction with halogens such as chlorine, fluorine, and bromine to produce for example, AlCl
3
(or Al
2
Cl
6
); or AlF
3
; or AlBr
3
(or Al
2
Br
6
). The aluminum-fluorine compounds can flake off the surfaces of process apparatus parts, causing an eroding away of the parts themselves, and serving as a source of particulate contamination of the process chamber (and parts produced in the chamber). Most of the compounds containing aluminum and chlorine, and many of the compounds containing aluminum and bromine, are gaseous under semiconductor processing conditions and leave the aluminum structure, creating voids which render the structure unstable and produce a surface having questionable integrity.
A preferred means of protecting the aluminum surfaces within process apparatus has been an anodized coating. Anodizing is typically an electrolytic oxidation process that produces an integral coating of aluminum oxide on the aluminum surface. Despite the use of anodized protective layers, the lifetime of anodized aluminum parts in semiconductor processing apparatus, such as susceptors in CVD reactor chambers and gas distribution plates for etch process chambers, has been limited due to the gradual degradation of the protective anodized film. Failure of the protective anodized film leads to excessive particulate generation within the reactor chamber, requiring maintenance downtime for replacing the failed aluminum parts and for cleaning particulates from the rest of the chamber.
Miyashita et al., in U.S. Pat. No. 5,039,388, issued Aug. 13, 1991, describe a plasma forming electrode used in pairs in a semiconductor processing chamber. The electrode is formed from a high purity aluminum or an aluminum alloy having a chromic acid anodic film on the electrode surface. The chromic acid anodized surface is said to greatly improve durability when used in a plasma treatment process in the presence of fluorine-containing gas. The electrode is described as formed from a high purity aluminum such as JIS 1050, 1100, 3003, 5052, 5053, and 6061, or similar alloys such as Ag—Mg alloys containing 2 to 6% by weight magnesium.
U.S. Pat. No. 5,756,222, to Bercaw et al., issued May 26, 1998, and entitled “Corrosion-Resistant Aluminum Article For Semiconductor Processing Equipment”, describes an article of manufacture useful in semiconductor processing which includes a body formed from a high purity aluminum-magnesium alloy having a magnesium content of about 0.1% to about 1.5% by weight, either throughout the entire article or at least in the surface region which is to be rendered corrosion-resistant, and an impurity atom content of less than 0.2% by weight. Impurity atoms particularly named include silicon, iron, copper, chromium, and zinc. The high purity aluminum-magnesium alloy may be overlaid by a cohesive film which is permeable to fluorine, but substantially impermeable to oxygen. Examples of such a film include aluminum oxide or aluminum nitride. The subject matter disclosed in this patent is hereby incorporated by reference in its entirety.
U.S. Pat. No. 5,811,195, to Bercaw et al., issued Sep. 22, 1998, and entitled “Corrosion-Resistant Aluminum Article For Semiconductor Equipment”, further discloses that the magnesium content of the aluminum article may be in the range of about 0.1% to about 6.0% by weight of the aluminum article. However, for operational temperatures of the article which are greater than about 250° C., the magnesium content of the aluminum article should range between about 0.1% by weight and about 1.5% by weight of the article. In addition, an article is described in which the impurities other than magnesium may be as high as about 2.0% by weight in particular instances. One example is when there is a film overlying the exterior region of the article body, where the film comprises aluminum oxide or aluminum. Another example is where there is a magnesium halide layer having a thickness of at least about 0.0025 &mgr;m over the exterior surface of the aluminum article. The subject matter disclosed in this patent is hereby incorporated by reference in its entirety.
For an aluminum alloy to be useful in the fabrication of semiconductor processing apparatus, it must not only exhibit low level of impurity atoms, but it must also have desirable mechanical properties. The mechanical properties must enable machining to provide an article having the desired dimensions. For example, if the alloy is too soft, it is difficult to drill a hole, as material tends to stick during the drilling rather than to be removed by the drill. Controlling the dimensions of the machined article is more difficult. There is penalty in machining cost. The mechanical properties of the article also affect the ability of the article to perform under vacuum. For example, a process chamber must exhibit sufficient structural rigidity and resistance to deformation that it can be properly sealed against high vacuum. Finally, when the article is treated, to reduce stress, for example, the treatment must ensure that there is uniform transfer of loads and stresses.
The “Metals Handbook”, Ninth Edition, Volume 2, copyright 1979, by the American Society for Metals, describes the heat treatment of aluminum alloys, beginning at page 28. In particular, for both heat-treatable and non-heat-treatable aluminum alloys, annealing to remove the stress created during cold work is accomplished by heating within a temperature range from about 300° C. (for batch treatment) to about 450° C. (for continuous treatment).
In general, the term “heat treatment” applied to aluminum alloys is said to be restricted to the specific operations employed to increase strength and hardness of precipitation-hardenable wrought and cast alloys. These are referred to as “heat-treatable” alloys, to distinguish them from alloys in which no significant strengthening can be achieved by heating and cooling. The latter are generally said to be referred to as “non-heat-treatable” alloys, which, in wrought form, depend primarily on cold work to increase strength. At page 29 of the “Metals Handbook”, Table 1 provides typical full annealing treatments for some common wrought aluminum alloys. The 5xxx series of aluminum alloys are of intere

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