Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-05-07
2001-02-27
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230MW, C118S725000, C156S345420
Reexamination Certificate
active
06192828
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a thin film forming device for forming a thin film on a base material by the plasma CVD (Chemical Vapor Deposition) method. More particularly, the present invention relates to the device capable of forming an excellently crystalline thin film without heating a base material to high temperature.
2. Description of the Related Art
In order to manufacture a thin film transistor (TFT) for composing a liquid crystal display, a semiconductor integrated circuit or a solar battery, a thin crystalline film is formed on a base material, for example, a thin silicon film is formed on the base material.
One of the means for forming the thin crystalline film is the plasma CVD method. According to the plasma CVD method, raw material gas is decomposed in plasma so that a thin film is formed on the base material. Therefore, the plasma CVD method is advantageous in that the base material can be kept at a relatively low temperature.
FIG. 5
is a view showing a conventional example of a thin film forming device to which the plasma CVD method is applied. In a reaction chamber container
2
, from which gas is exhausted to vacuum by a vacuum exhauster not shown in the drawing, there are provided a base material holder
8
for holding a base material
10
, and a high frequency electrode
12
which are opposed to each other. In the base material holder
8
, a heater
9
is provided for heating the base material. Raw material gas
6
such as silane (SiH
4
/H
1
) diluted by hydrogen is introduced into the reaction chamber container
2
via a gas introduction pipe
4
. Electric power of high frequency is supplied between the high frequency electrode
12
and the base material holder
8
from a high frequency electric power source
16
via a matching circuit
18
.
When the raw material gas
6
is introduced and the electric power of high frequency is supplied as described above, electric discharge of high frequency is generated between the high frequency electrode
12
and the base material holder
8
. By this electric discharge of high frequency, the raw material gas
6
is ionized and plasma
20
is generated. The raw material gas
6
is decomposed in this plasma
20
, and a thin film is formed on the base material
10
, for example, a thin film of silicon is formed on the base material
10
.
In the above thin film formation device, the plasma CVD method is used. Therefore, it is possible to keep the base material at a relatively low temperature. However, in order to form a thin crystalline film, it is necessary to heat the base material
10
to at least 900° C. by the heater
9
. Therefore, the base material
10
must withstand this temperature. For the above reasons, a type of the base material
10
is limited. For example, glass of a low softening point such as soda glass or non-alkali glass, the softening point of the former is approximately 400° C. and the softening point of the latter is approximately 700° C., is not expensive. However, it is impossible to use the above glass of a low softening point in the conventional device.
Further, since the base material
10
is directly exposed to the plasma
20
, ions existing in the plasma
20
having energy of various intensities are incident on a surface of the base material
10
. The ions having energy of various intensities are incident on the base material
10
, and the ions are always incident in the process of film formation. Consequently, an excessively large quantity of ions are incident on the base material
10
. Therefore, growth of crystals of the thin film formed on the base material is obstructed, and damage (defect) is caused on the film, that is, it is difficult to form an excellently crystalline thin film.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a thin film formation device capable of forming an excellently crystalline thin film without heating a base material to high temperature.
A thin film forming device for forming a silicon thin film having crystallinity according to the present invention comprises: a film formation chamber container from which gas is exhausted to vacuum; an insulating member; a plasma chamber container which is adjacent to the film formation chamber container via the insulating member so that the plasma chamber container is insulated from the film formation chamber container and is communicated with the film formation chamber container, at least one of raw material gas and a mixture gas containing raw material gas and inert gas being introduced into the plasma chamber container; plasma generation means for generating plasma in the plasma chamber container by ionizing the introduced raw material gas; a porous electrode having small pores arranged to partition the plasma chamber container and the film formation chamber container from each other, the electric potential of the porous electrode being the same as that of the plasma chamber container; a base material holder for holding a base material so that the base material can be directed to the porous electrode, the base material holder being arranged in the film formation chamber container to be opposed to the porous electrode; and a pulse power source for impressing a bipolar pulse voltage, in which a positive polarity portion and a negative polarity portion are alternately repeated, between the base material holder and both of the plasma chamber container and the porous electrode of the same electric potential as that of the plasma chamber container.
REFERENCES:
patent: 4828369 (1989-05-01), Hotomi
patent: 5302424 (1994-04-01), Murai et al.
patent: 5968275 (1999-10-01), Lee et al.
patent: 6050217 (2000-04-01), Li
patent: 6-45254 (1994-02-01), None
patent: 9-251958 (1997-09-01), None
Kirimura Hiroya
Takahashi Eiji
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hassanzadel P.
Mills Gregory
Nissin Electric Co. Ltd.
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