Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2002-07-08
2003-09-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S030000, C438S781000, C438S099000
Reexamination Certificate
active
06617263
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for flattening an organic film and a method for manufacturing a liquid crystal display device using the same. More particularly, the present invention relates to a method for flattening an organic film that flows a long distance with high controllability and a method for manufacturing an active matrix substrate (TFT substrate) of a liquid crystal display device using the method for flattening an organic film.
2. Description of the Related Art
In conventional technologies for flattening an uneven surface of a substrate having semiconductor devices formed thereon, there has been conceived a flattening method for coating an organic film on the uneven surface of the substrate and heating the organic film to fill concave due to the uneven surface of the substrate with the organic film to thereby flatten the uneven surface of the substrate.
Japanese Unexamined Patent Application Publication No. 7-120784 discloses an example using the above-mentioned flattening method and is explained with reference to a cross-sectional view shown in
FIGS. 1A
to
1
C.
Referring to
FIG. 1A
, after a lower wiring layer
302
is formed on a glass substrate
301
, polyamide acid is spin-coated on the glass substrate
301
to a film thickness of 0.1 to 1 &mgr;m to cover the lower wiring layer
302
. Then, the polyamide acid film is heated at temperatures of 200 to 300° C. to be imidized, thereby forming an interlayer insulating film
303
consisting of a polyimide (refer to FIG.
1
B). Subsequently, an upper wiring layer
304
is formed on the interlayer insulating film
303
and a polyimide film is formed to cover the upper wiring layer
304
in accordance with the same method as that employed to form the interlayer insulating film
303
to thereby constitute an insulating protective film
311
(refer to FIG.
1
C).
As mentioned above, both the interlayer insulating film
303
and the insulating protective film
311
are formed by spin-coating polyamide acid solution on the associated surface. Therefore, the concaves of the uneven surface of the substrate due to the lower wiring layer
302
and the upper wiring layer
304
are filled with the polyamide acid to flatten the surfaces of the interlayer insulating film
303
and the insulating protective film
311
.
However, after coating the polyamide acid by using the spin coater, the organic insulating film is subjected to heat treatment at temperatures of 200 to 300° C. for several tens minutes to one hour. In a case where the lower wiring layer and the upper wiring layer consist of aluminum, it has been found that problems associated with the heat treatment appears as hillock of aluminum. Moreover, the thermal reflow performed at temperatures over 200° C. imparts thermal stress to the underlying aluminum.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a flattening method for easily flattening an uneven surface of a substrate having an underlying film formed thereon by forming an organic film on the substrate and subjecting the organic film to a heat treatment at temperatures of 200° C. or less to cause reflow of the organic film, and a method for manufacturing a liquid crystal display device using the flattening method.
A method for flattening an organic film according to the present invention comprises the steps of forming an organic film on a surface of an insulating substrate and infiltrating an organic solvent into the organic film, and causing dissolution of the organic film to flatten the organic film.
The method for flattening an organic film according to the present invention is constructed such that the organic film is an organic material capable of dissolving into the organic solvent, the organic material is any one of acrylic, polyimide and polyacrylicamide, and the organic solvent includes at least one selecting from the group consisting of Alcohols, Ethers, Esters, Ketones, Glycols, Alkylene, glycols, Alkoxy alcohols and Glycol ethers.
The method for flattening an organic film according to the present invention is further constructed such that the organic film is subjected to heat treatment at temperatures of 100 to 180° C. to evaporate the organic solvent included in the organic film after the step for causing dissolution of the organic film to flatten the organic film.
As mentioned above, after coating a surface of the insulating substrate with the organic film, the organic solvent is infiltrated into the organic film to cause the dissolution of the organic film, thus flattening the organic film. Furthermore, after flattening the organic film, the heat treatment for evaporating the organic solvent included in the organic film is performed at relatively low temperatures, i.e., temperatures of 100 to 180° C. and therefore, the thermal stress applied to a material wiring layer as a lower layer covered with the organic film is reduced.
A method for manufacturing a liquid crystal display device according to the present invention is constructed as follows. That is, the liquid crystal display device is formed by disposing a TFT substrate and an opposing substrate facing each other and interposing a liquid crystal the TFT substrate and the opposing substrate. In this case, the TFT substrate is formed by the steps of forming a gate line and a gate electrode on a first substrate, forming a gate insulating film covering the gate line and the gate electrode on the first substrate, forming a semiconductor film on the gate insulating film and then, forming a source/drain electrode on the semiconductor film to connect the source/drain electrode to the semiconductor film, forming a protective film covering the semiconductor film and the source/drain electrode on the gate insulating film and forming a flattened film on the protective film, in which the step for forming a protective film is performed such that an organic film is coated on the protective film and an organic solvent is infiltrated into the organic film to cause dissolution of the organic film.
As described above, according to the method for forming the liquid crystal display device, the flattened film on the protective film of the TFT substrate is formed by infiltrating the organic solvent into the organic film to cause reflow of the organic film to flatten the organic film after coating the organic film on the protective film, and further, the organic film is subjected to heat treatment at relatively low temperatures, i.e., temperatures of 200° C. or less, thereby reducing thermal stress applied to wiring layers covered by the organic film.
REFERENCES:
patent: 6388271 (2002-05-01), Mitlehner et al.
patent: 6420200 (2002-07-01), Yamazaki et al.
patent: 7-120784 (1995-05-01), None
Isaac Stanetta
NEC LCD Technologies Ltd.
Niebling John F.
Young & Thompson
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