Coating processes – Coating by vapor – gas – or smoke
Patent
1998-05-29
1999-07-13
King, Roy V.
Coating processes
Coating by vapor, gas, or smoke
427255, 427314, 4271263, C23C 1640
Patent
active
059224053
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for coating a substrate with an aluminum oxide film by chemical vapor deposition using a dialkylaluminum alkoxide compound as an aluminum source.
BACKGROUND OF THE INVENTION
There have hitherto been reported a number of chemical vapor deposition (CVD) methods for the preparation of an aluminum oxide film. These methods are well summarized in recent review by E. Fredriksson et al., "Chemical Vapour Deposition of Aluminum Oxides from Various Gas Mixture," and J. Chemical Vapor Deposition, 1, 333-417 (1993) as well as in Korean translation of "CVD Handbook" pp 665-689 (Bando Publishing Co., Seoul, Korea, 1993). Aluminum trichloride and triisopropoxide have been most commonly used as aluminum sources in the CVD of an aluminum oxide film due to their low cost and ready availability. These conventional aluminum sources have low vapor pressures and are usually heated to higher than 100.degree. C. to generate a vapor stream to be used in a CVD process.
Further, trialkylaluminums have been used in the CVD of an aluminum oxide film, which are liquid at room temperature and have relatively high vapor pressure. However, such trialkylaluminums do not contain oxygen atoms, thus the use of an oxygen source such as O.sub.2 or N.sub.2 O is essential for the formation of an aluminum oxide film. Also trialkylaluminums are pyrophoric when exposed to air. U.S. Pat. No. 4,675,089 discloses a plasma-assisted CVD method of depositing an amorphous thin film of aluminum oxide using a trialkylaluminum vapor and carbon dioxide. However, this method requires expensive equipments to produce plasma and have lower throughput compared to a thermal CVD method, thus less suitable for use in a large-scale application.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an efficient and economical process for the preparation of an aluminum oxide film suitable for a large-scale production of articles coated with aluminum oxide film.
In accordance with one aspect of the present invention, there is provided a process for coating a substrate with an aluminum oxide film, which comprises contacting a vaporized dialkylaluminum alkoxide compound with said substrate heated to a temperature ranging from 300 to 600.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents an Auger electron spectrum of an aluminum oxide film deposited on SI(100) at 400.degree. C. using diethylaluminum isopropoxide in accordance with Example 6 of the present invention; and
FIG. 2 shows an Auger depth profile of the film obtained in Example 6.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized in that a dialkylaluminum alkoxide is used as an aluminum source in the chemical deposition of an aluminum oxide film.
The dialkylaluminum alkoxide useful for practicing the present invention is a material which has a high vapor pressure sufficient to vaporize under an ambient condition, i.e., 0.06 to 0.5 mmHg at a temperature ranging from 0 to 25.degree. C. The dialkylaluminum alkoxide compound suitable for use in the present invention is represented by the following formula: group.
The dialkylaluminum alkoxide compound according to the present invention may be prepared by reacting an alkylaluminum with an alcohol at a low temperature by a conventional method, e.g., as is described by Paul S. Coan, et al. in Organometallics, 8, 2724 (1989), or by reacting an alkylaluminum with an aluminum alkoxide in a molar ratio of 2:1 at room temperature.
The preferred dialkylaluminum alkoxide compound in practicing the present invention may be dimethylaluminum isopropoxide, diethylaluminumisopropoxide, dimethylaluminum t-butoxide and a mixture thereof. Under an ambient condition, dimethylaluminum isopropoxide is a liquid, whereas diethylaluminum isopropoxide and dimethylaluminum t-butoxide are gel-like solids.
In accordance with the present invention, the dialkylaluminum alkoxide compound is vaporized at an ambient temperature ranging from 0 to 20.de
REFERENCES:
patent: 5389401 (1995-02-01), Gordon
patent: 5496597 (1996-03-01), Soininen et al.
Kim Yun-Soo
Koh Won-Yong
Ku Su-Jin
King Roy V.
Korea Research Institute of Chemical Technology
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