Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2001-07-24
2003-05-06
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C428S689000, C428S696000, C428S698000, C428S704000, C501S118000, C501S119000, C501S151000, C501S153000
Reexamination Certificate
active
06558806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-resistant structural body, a halogen-based corrosive gas-resistant material and a halogen-based corrosive gas-resistant structural body.
2. Description of the Related Art
As wirings in the semiconductors and liquid crystal panels become finer, fine workings with dry processings are progressing. With the demand for such fine workings, a halogen-based corrosive gas is used as a film-forming gas or an etching gas for the semiconductors and the like. It is known that aluminum nitride exhibits high corrosion resistance against such a halogen-based corrosion gas. Therefore, members having aluminum nitride on their surfaces have been used in semiconductor-producing apparatuses, liquid crystal panel-producing apparatuses and the like.
When aluminum contacts the air, its surface is oxidized to form a thin oxidized film. Since this oxidized film is an extremely stable passive phase, the surface of aluminum could not be nitrided by a simple nitriding method. Under the circumferences, the following methods have been developed to modify the surface of aluminum and form aluminum nitride thereon.
JP-A-60-211061 discloses a method in which after the inner pressure of the chamber is reduced to a given level, and hydrogen or the like is introduced thereinto, discharging is conducted to heat the surface of a member such as aluminum to a given temperature, further argon gas is introduced and discharging is conducted to activate the surface of the member, and the surface of the aluminum member is ionically nitrided through introducing nitrogen gas. In addition, JP-A-7-166321 discloses a method in which a nitriding aid made of aluminum powder is contacted with the surface of the aluminum, and aluminum nitride is formed on the surface of aluminum through heating in a nitrogen atmosphere.
An aluminum nitride film itself has high heat resistance, high heat-cycling durability and high Vickers hardness. However, in such a technique that forms an aluminum nitride film on an aluminum substrate, the aluminum nitride film tends to peel off from the substrate when heat-cyclings are applied, depending on a difference in thermal expansions between the obtained aluminum nitride film and metallic aluminum or a state of an interface between the substrate and the aluminum nitride film.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve heat-cycling durability of a structural body in which a nitrided material is provided on a substrate containing at least metallic aluminum.
It is another object of the present invention to further improve halogen-based corrosive gas-resistance of a structural body comprising a substrate containing at least metallic aluminum and a nitrided material formed on the substrate.
It is yet another object of the present invention to provide a nitrided material having high resistance against hydrofluoric acid and a halogen-based corrosive gas and high heat-resistance.
The present invention relates to a heat-resistant structural body comprising a substrate containing at least metallic aluminum and a nitrided material formed on the substrate, wherein the nitrided material is composed mainly of an aluminum nitride phase and a metallic aluminum phase.
The present inventors found that such a lamination structural body had higher heat resistance, especially heat-cycling durability than a structural body where an aluminum nitride film was formed on metallic aluminum. The reason of this is not clear, but it is considered that since the film is the mixed phase of aluminum nitride phase and the metallic aluminum phase, the film has a closer expansion coefficient to aluminum of the substrate than the aluminum nitride film does, so that stress on the interface between the substrate and the nitrided material is relaxed.
In the present invention, the nitrided material may be composed mainly of the aluminum nitride phase and the metallic aluminum phase, and other crystal phase or amorphous phase may exist. However, the total amount of the aluminum nitride phase and the metallic aluminum phase is preferably not less than 80 mol %, and more preferably not less than 90 mol %.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In a preferred embodiment, the nitrided material contains at least one metallic element selected form Group 2A, Group 3A, Group 4A and Group 4B in Periodic Table.
In a particularly preferred embodiment, the nitrided material contains at least one metallic element selected from Group 2A, Group 3A and Group 4A in Periodic Table. By incorporating such a metallic element, resistances of this structural body against the halogen-based corrosion gas, especially fluorine-based corrosive gas was found to be significantly improved.
That is, it is known that the halogen-based corrosive gas and its plasma used in semiconductor producing processes etc. exhibit strong chemical and physical interactions with the substrate to be treated. Silicon, silicon oxide and the like are etched by using these interactions. The present inventors exposed a various kind of the structural bodies to the halogen-based corrosive gas, and, as a result, found that the durability of the structural body against chemical corrosion of the plasma of the halogen-based corrosive gas was improved by incorporating at least one metallic element selected from Group 2A, Group 3A, Group 4A and Group 4B in Periodic Table into the nitrided material. That is, the present inventors found that the above-mentioned metallic element contained in the nitrided material reacts with the halogen gas and its plasma to accelerate a formation of a passive film on the surface of the nitrided material. The corrosion was inhibited from extending into the nitrided material by the passive film.
The passive film itself is physically etched in the plasma of the halogen-based corrosive gas by receiving a bombardment of the high-energy gas. However, at least one metallic element selected from Group 2A, Group 3A and Group 4A in Periodic Table existing in the nitrided material and the underlying substrate reproduce the passive film by diffusing toward the surface of the nitrided material. Therefore, the number of reproducing the passive film, or the resistivity was found to depend on the concentrate of the above-mentioned metallic element(s) in the film and the substrate.
Summarizing the findings in the above, the structural body of the present invention has two features:
(1) the nitrided material on the surface absorbs a difference between the substrate in the thermal expansions as the mixed film of the aluminum nitride phase and the metallic aluminum phase; and
(2) by incorporating at least one metallic element selected from Group 2A, Group 3A and Group 4A into Periodic Table at least in the nitrided material, when the structural body is exposed to the halogen-based corrosive gas and its plasma, especially to the fluorine-based gas and its plasma, the chemical corrosion resistance against these gases and plasmas is improved by the passive film formed on the surface by halide, which is formed with the metallic element.
By combining these features, the structural body of the present invention is extremely stable even under such a circumstance that exposes the structural body to the halogen-based corrosive gas and its plasma, especially under a circumstance that causes such exposure of the structural body at a high temperature of not less than 200° C.
Among the metallic element selected from Group 2A, Group3A and Group 4A in Periodic Table, the nitrided material preferably contains magnesium, since magnesium acts effectively in the process of forming the nitride film as well as it is one of metal elements having an especially low vapor pressure of a fluoride formed upon exposing to the fluorine-based gas.
In a preferred embodiment, the nitrided material contains 1-10 atm % of at least one metallic element selected from Group 2A, Group 3A and Group 4A in Periodic Table. More preferably, the nitrided material contains not less than 3 atm % of the metallic el
Blackwell-Rudasill G. A.
Burr & Brown
Jones Deborah
NGK Insulators Ltd.
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