Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
2001-12-27
2004-08-24
Meeks, Timothy (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
C427S255330, C427S256000, C427S299000, C427S300000
Reexamination Certificate
active
06780465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to methods for making thin film patterns using chemical vapor deposition (CVD).
2. Description of Related Art
In chemical vapor deposition (CVD), the material for the thin film is fed in a gaseous form to a substrate, and the gas is decomposed by heat, light, etc., so that a desired thin film is deposited on or over the substrate. This process is widely used as a method for making thin films, for example, semiconductor films, insulating films, and conductive films, in the process of manufacturing semiconductor apparatus. In the CVD process, a vaporized substance that is obtained by vaporizing a liquid may be used as a raw material. The CVD process using organometallic compounds is particularly referred to as “metal organic chemical vapor deposition” (MOCVD). In general, the gaseous materials and the vaporized substances of liquid materials are produced outside of a reaction chamber and are introduced into the reaction chamber via pipes.
In the process of manufacturing semiconductor apparatus, after a thin film is formed over the entire surface of a substrate, a patterning step is performed in which unnecessary parts are removed, leaving necessary parts of the thin film. The patterning step is usually performed as follows. First, a resist film is formed on the thin film, and the resist film is then irradiated with light through a photomask to form a resist pattern. Unnecessary parts of the thin film are then removed by etching using the resist pattern as a mask. Next, the resist pattern is removed.
Additionally, since CVD deposition is accompanied with a chemical reaction, it is also possible to only form a thin film in necessary regions (selective growth) by bringing about an inactive state in regions in which the thin film is unnecessary on the substrate.
However, in the conventional CVD and MOCVD processes, since hazardous gases which are highly reactive are introduced into a reaction chamber, leakage of the gases from the reaction chamber must be prevented during reaction, and the gases must be reliably recovered after the reaction. For this purpose, in a conventional CVD system and MOCVD system, large-scale vacuum exhaust units are provided. A portion of the gas introduced into the reaction chamber is subjected to reaction to form a thin film, and most of the gas must be recovered and neutralized.
As described above, since a method for making thin films using the conventional CVD process requires a large-scale vacuum exhaust unit or neutralization unit, there is room for a reduction in costs.
In particular, with respect to large liquid crystal displays, etc., an array of switching elements for corresponding pixels must be formed on a large area substrate, and if the array is formed by the conventional method (in which the patterning step is performed after the thin film is formed over the entire surface of the substrate), the amount of the thin film that is left on the substrate is significantly small, and most of the thin film is removed in the patterning step.
Additionally, even where the thin film is selectively grown using a CVD process, under the existing conditions, a step is required in which portions protruding from the pattern of the thin film are removed. That is, although the amount of the thin film to be removed can be decreased by selectively growing the thin film using the CVD process, even in such a case, it is still necessary to remove the unnecessary thin film after the thin film is formed.
As described above, in the method for producing large liquid crystal displays, etc., using the method for forming thin films using the conventional CVD process, the raw materials for the thin films are wasted, which is disadvantageous.
On the other hand, Japanese Unexamined Patent Application Publication No. 2000-12465 discloses a method for simultaneously forming silicon films on both film formation surfaces of a first member for forming the silicon film and a second member for forming the silicon film. In this method, the first member for forming the silicon film, in which a liquid raw material is applied on the film formation surface, and the second member for forming the silicon film are placed so as to face each other.
In accordance with this method, a silicon film is formed on the film formation surface of the first member for forming the silicon film by a decomposition reaction of the liquid raw material applied, and a silicon film is formed on the film formation surface of the second member for forming the silicon film by a decomposition reaction of a vaporized substance from the liquid raw material on the film formation surface of the first member for forming the silicon film. According to this publication, the simultaneous formation of silicon films on two substrates, and the formation of the silicon film with a uniform thickness over the entire surface of the second member for forming the silicon film, are mentioned as advantages of the invention.
However, in the method according to this publication, a patterning step must also be performed after the formation of the thin films in order to obtain a silicon thin film with a predetermined pattern.
SUMMARY OF THE INVENTION
The present invention addresses the problems associated with the conventional techniques described above. Thus, the present invention provides a method for forming a thin film using a CVD process in which a large-scale vacuum exhaust unit or neutralization unit is not required, and the thin film can be formed partially on a substrate using a small amount of raw material liquid. The invention also provides a method in which a thin film pattern is obtained, even without performing a patterning step after the formation of the thin film.
In order to address the problems described above, the present invention provides a method for forming a thin film using chemical vapor deposition, in which a liquid containing a raw material for the thin film is placed on a part or a plurality of parts of a substrate, and the raw material for the thin film is vaporized from the liquid so as to be fed to a part or a plurality of parts of the surface for forming the thin film, and thereby the thin film is formed with a predetermined pattern on the surface for forming the thin film.
In one aspect of the present invention, a method for forming a thin film by chemical vapor deposition includes the steps of: placing a liquid containing a raw material for the thin film on a part or a plurality of parts of a substrate; and vaporizing the raw material for the thin film from the liquid so as to be fed to a part or a plurality of parts of the surface for forming the thin film to form the thin film with a predetermined pattern on the surface for forming the thin film.
In accordance with this method, even where a thin film pattern in which a thin film is present on a significantly small part of a large area substrate is formed, the amount of the raw material for the thin film to be used can be significantly decreased. Additionally, since it is not necessary to introduce the raw material for the thin film in the gaseous state into a reaction chamber, a large-scale vacuum exhaust unit or neutralization unit is not required.
Examples to perform such a method are described below.
(1) In the method for forming the thin film, one surface of the substrate is used as a surface to place the liquid, and the thin film is formed in a region other than the region in which the liquid is placed on the surface to place the liquid.
In accordance with the method described above, by only using a substrate to form a thin film, without using a dummy substrate to place a liquid, it is possible to form a thin film pattern on the substrate.
(2) In the method for forming the thin film, a first substrate to place the liquid and a second substrate to form the thin film are placed so that the surface to place the liquid of the first substrate faces the surface to form the thin film of the second substrate, and the raw material for the thin film is vaporized from the liquid p
Furusawa Masahiro
Shimoda Tatsuya
Meeks Timothy
Seiko Epson Corporation
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