Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
2000-04-21
2002-06-18
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230ER, C118S728000, C438S710000
Reexamination Certificate
active
06406590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface treatment method and apparatus using plasma, and more particularly to a surface treatment method and apparatus for forming a film or modifying a surface in a multilayer structure device such as a semiconductor device and a liquid crystal device, and for forming a film of various functional materials or modifying a surface, using high-pressure plasma at high speed and under clean atmosphere. The word “surface treatment” generically includes the above-described film formation and surface modification.
2. Description of the Related Art
Plasma CVD is known as a method for forming a film in a multilayer structure of various devices such as a semiconductor device and a liquid crystal device or a film of various functional materials. The plasma CVD is now widely used in actual manufacturing processes. Plasma is also used in a known method for modifying a surface.
In the above-described plasma CVD or plasma surface modification method, reactive gas is selected in accordance with target film formation or surface modification. A high electric field is applied to the selected gas to be in a plasma state. Using active seeds generated in the plasma, a film is formed on a target surface or a target surface is modified. There are various techniques of generating plasma. In these techniques, plasma generation may be performed in various ranges of pressure and the like. The range of the applied preesure is not clearly defined. When plasma generation is performed under a low pressure, the density of the active seeds is low, so that the rate of film formation or surface modification is slow. For this reason, the throughput of an apparatus is small, contributing to an increase in cost of the product.
To solve the above-described problems and improve the rate of film formation or surface modification, the plasma generation may be performed under a high pressure which is as high as atmospheric pressure so that the density of the active seeds is increased. This method is, for example, disclosed by Japanese Laid-Open Publication Nos. 2-50969, 2-73978, or 2-73979. Hereinafter, a method disclosed by Japanese Laid-Open Publication No. 2-73978 will be described with reference to FIG.
24
.
FIG. 24
is a diagram illustrating a configuration of an apparatus disclosed in the above-described publication. In
FIG. 24
, the apparatus includes a film formation chamber
241
, a non-ground electrode
242
, a ground electrode
243
, a porous plate high resistor
244
, a sample substrate
245
, a gas inlet
246
, a RF power supply
247
, a heater
248
, and a gas outlet
249
.
According to the above-described publication, the electrodes
242
and
243
are arranged to face each other in the film formation chamber
241
. The RF power supply
247
is connected to the non-ground electrode
242
. The ground electrode
243
is connected to the ground. A high resistor (not shown), which has a size greater than or equal to the ground electrode
243
, is optionally provided on the ground electrode
243
. The sample substrate
245
is provided on the high resistor. The porous plate high resistor
244
is attached to the non-ground electrode
242
. A gas mixture of a gas for film formation and He gas is supplied into the film formation chamber
241
from the inside of the non-ground electrode
242
through the holes of the porous plate high resistor
244
. The supplied gas is simultaneously discharged from the gas outlet
249
so that the inside of the film formation chamber
241
keeps a pressure around the atmospheric pressure. In this case, when a distance between the porous plate high resistor
244
and the sample substrate
245
is defined as a intersubstrate gap
240
g
, the intersubstrate gap
240
g
is between or equal to 0.1 mm and 10 mm.
In the above-described structure, radio frequency power is supplied to the non-ground electrode
242
from the RP power supply
247
. Atmospheric pressure plasma
240
p
is generated between the non-ground electrode
242
and the ground electrode
243
so that the film formation is performed on the sample substrate
245
.
Experiments on the film formation were conducted using the conventional apparatus shown in FIG.
24
. The conditions of the experiments are shown below in Table 1. The results of the experiments are shown below in Tables 2 and 3. Table 2 indicates a correlation between the intersubstrate gap
240
g
and a film thickness distribution. Table 3 indicates a correlation between a value Q/S and a film formation rate in the central portion of the substrate
245
, where the value Q/S is obtained by dividing an overall gas flow amount Q by the plasma volume S.
TABLE 1
{circle around (1)}
{circle around (2)}
{circle around (3)}
Material gas
SiH
4
CH
4
TiCl
4
+ NH
3
Material gas/He
SiH
4
/He
CH
4
/He
CH
4
/He NH
3
/He
Temperature of substrate
250° C.
250° C.
700° C.
Pressure
Atmospheric pressure
Rf power
200 W
RF frequency
13.56 MHz
Area of electrode
10 × 10 cm
2
High resistor,
3 mm
substrate-to-substrate distance
High resistor
Quartz glass
Substrate
Quartz glass (10 × 10 cm
2
)
Thin film
&agr;-Si
&agr;-C
TiN
TABLE 2
Subtrate-to-substrate
{circle around (1)}
{circle around (2)}
{circle around (3)}
distance (mm)
&agr;-Si
&agr;-C
TiN
15
±25%
±22%
±27%
10
±7%
±9%
±7%
5
±5%
±6%
±6%
3
±4%
±4%
±5%
1
±6%
±5%
±7%
TABLE 3
{circle around (1)}
{circle around (2)}
{circle around (3)}
Q/(sec)
&agr;-Si
&agr;-C
TiN
10
−1
Only dust
0.08
0.10
10
0
2.8
3.1
2.7
10
1
28.7
24.3
21.8
10
2
3.1
2.8
2.3
10
3
0.08
0.11
0.14
As is seen from Tables 1 through 3, the apparatus disclosed in the above-described publication has the following features:
(1) the material gas for the film formation is diluted with a large amount of He gas for the purpose of obtaining a stable glow discharge;
(2) to form a uniform film over a large area, the high resistor
244
is provided on at least one of the electrodes
242
and
243
. For this reason, a direct current does not flow, but only an alternating current flows. A current density per unit area is thus restricted, so that the plasma
240
p
can be uniformly spread:
(3) according to the experiment results shown in Table 2, the smaller the gap
240
g
between the sample substrate
245
and the high resistor
244
, the smaller and more uniform the film thickness distribution of the obtained film. For this reason, the gap
240
g
between the sample substrate
245
and the high resistor
244
is set to 10 mm to 0.1 mm: and
(4) according to the experiment results shown in Table 3, when the value Q/S which is obtained by dividing the overall gas flow amount Q by the discharge space volume S is 10
−1
sec
−1
, the supplied material gas is quickly decomposed. The film formation rate on the substrate
245
is decreased. On the other hand, when the value Q/S is large, the supply gas passes through the plasma
240
p
for a short time. The supplied gas substantially is not thus decomposed. The film formation rate is decreased and the material gas is not effectively used. For this reason, the mixture gas of the material gas for film formation and the He gas is supplied into the discharge space at a Q/S of 1 sec
−1
to 10
2
sec
−1
so that the gas in the whole discharge space is replaced in 10
−2
sec to 1 sec.
The above-described conventional technology has the following problems.
The film formation chamber
241
is filled with the mixture gas of the material gas for film formation and the He gas so that the pressure inside the chamber
241
is around the atmospheric pressure. The high-pressure plasma
240
p
is generated under such a high-pressure atmosphere. The plasma
240
p
decomposes the material gas for film formation. The decomposed material forms a film on the sample substrate
245
. Because the film formation chamber
241
is filled with the mixture gas around the atmospheric pressure, r
Ebata Yusuke
Okuda Tohru
Hassanzadeh P.
Mills Gregory
Sharp Kaubushiki Kaisha
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