Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1997-07-10
2002-10-15
Chen, Bret (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S577000, C427S535000
Reexamination Certificate
active
06465057
ABSTRACT:
TECHNICAL FIELD
The present invention relates to plasma CVD method and apparatus for forming a film on a substrate to be deposited, i.e., a deposition target object by forming a plasma from a deposition material gas and by exposing the object to the plasma.
BACKGROUND ART
A plasma CVD method has been widely used for manufacturing various kinds of semiconductor devices such as ICs and sensors utilizing semiconductors, manufacturing various kinds of thin-film devices used in solar cells and LCDs (liquid crystal displays), forming films having a high wear resistance on mechanical parts and tools requiring a high wear resistance, and others. Various apparatuses for implementing the plasma CVD method have been known, and a plasma CVD apparatus of a capacity coupling type shown in
FIG. 8
is an example of such an apparatus.
The apparatus shown in
FIG. 8
is known as a parallel-plated plasma CVD apparatus, and has a vacuum container
1
used as a deposition chamber, in which an electrode
2
also serving as an object holder for carrying a substrate S, i.e., a deposition target object S as well as an electrode
3
opposed to the electrode
2
are arranged.
The electrode
2
is usually used as a ground electrode, and is additionally provided with a heater
21
for heating the object S mounted thereon to a deposition temperature. When the object S is heated by a radiation heat, the heater
21
is separated from the electrode
2
.
The electrode
3
is an electric power applying electrode for applying an electric power to a deposition material gas, which is introduced between the electrodes
2
and
3
, for forming a plasma. In the illustrated example, the electrode
3
is connected to an RF (radio-frequency) power source
32
via a matching box
31
.
The vacuum container
1
is connected via piping to an exhaust device
5
, and is also connected via a piping to a gas supply unit
4
of the deposition material gas. The gas supply unit
4
includes one or more gas sources
431
,
432
, . . . for supplying deposition material gases connected to mass flow controllers
411
,
412
, . . . and valves
421
,
422
, . . . .
According to this parallel-plated plasma CVD apparatus, the deposition target object S is transported into the vacuum container
1
by an unillustrated object transporting device, and is mounted on the electrode
2
. The exhaust device
5
operates to achieve a predetermined degree of vacuum in the container
1
, and the gas supply unit
4
supplies the deposition material gas into the container
1
. The RF electrode
3
is supplied with an RF power from the power source
32
, and thereby the plasma is produced from the introduced gas. A film is deposited on the surface of the object S in the plasma thus produced.
A plasma CVD apparatus of an induction coupling type shown in
FIG. 9
has also been used. This apparatus differs from the apparatus in
FIG. 8
in that the object holder
2
is electrically floated, the electrode
3
in
FIG. 8
is replaced with an induction coil electrode
7
wound around the container
1
, and the matching box
31
and the RF power source
32
are connected to the opposite ends of the induction coil
7
. Structures other than the above are the same as those of the apparatus in
FIG. 8
, and the same or similar parts and portions bear the same reference numbers.
A plasma CVD apparatus shown in
FIG. 10
has also been used for forming high adherence films for engineering purposes and other films. The apparatus in
FIG. 10
differs from the apparatus in
FIG. 8
in that the electrode
2
also serving as the object holder is used as the power applying electrode for applying the electric power, and the electrode
3
opposed to the electrode
2
is used as the ground electrode. In the illustrated example, the electrode
2
is connected to the RF power source
32
via the matching box
31
. Structures other than the above are the same as those of the apparatus in
FIG. 8
, and the same or similar parts and portions bear the same reference numbers.
In this apparatus, ionized particles in the plasma apply an impact against the object S carried by the power applying electrode
2
. Therefore, this apparatus can be suitably used for manufacturing tools, machine parts and others. In the apparatus shown in
FIG. 8
, ionized particles apply a less impact against the object S, so that the deposition target object S can be selected from a wider range.
In the apparatus in
FIG. 10
, a self-bias voltage appears on the RF electrode
2
, and affects the quality of the deposited film. Generally, the deposition under the conditions of such a large self-bias voltage can achieve effects such as improvement of a deposition rate and improvement of a film hardness, although the latter depends on a kind of the film.
A plasma CVD apparatus shown in
FIG. 11
is also available. This apparatus differs from the apparatus in
FIG. 8
in that an RF power generating device
33
is employed instead of the RF power source
32
, and is connected to the electrode
3
via the matching box
31
. The RF power generating device
33
includes an RF power amplifier
34
and an RF arbitrary waveform generating device
35
connected thereto. Structures other than the above are the same as those of the apparatus in
FIG. 8
, and the same or similar parts and portions bear the same reference numbers.
According to this apparatus, formation of the plasma from the deposition material gas is performed by applying an RF power, on which pulse modulation or another modulation is effected, from the RF power generating device
33
to the electrode
3
.
Although not shown, such plasma CVD apparatuses are also known that differ from the parallel-plated plasma CVD apparatuses in
FIGS. 8 and 10
, respectively, in that the matching box
31
and the RF power source
32
in
FIGS. 8 and 10
are replaced with a DC power source capable of turning on/off a current. According to these apparatuses, formation of the plasma from the deposition material gas is performed by applying the DC power in a pulse form.
Although not shown, such a method has already been known that forms a plasma from the deposition material gas by applying a modulated RF power by using the induction coupling type-plasma CVD apparatus in
FIG. 9
provided with RF power generating device
33
shown in
FIG. 11
instead of the RF power source
32
.
Various kinds of films can be formed by the plasma CVD apparatuses in the prior art already described. For example, the pressure in the vacuum container
1
is set to about several hundreds of millitorrs, and the deposition material gas supply unit
4
supplies a carbon compound gas such as a methane (CH
4
) gas or an ethane (C
2
H
6
) gas, or a mixture of such a carbon compound gas and a hydrogen (H
2
) gas, whereby a carbon (C) film is formed on the deposition target object S.
In this case, the film quality can be controlled by changing the processing temperature of the deposition target object S. For depositing a film on an object made of, e.g., a synthetic resin such as polyimide, the deposition temperature is set to about 100° C. or less in view of the heat resistance of the object, in which case a diamond-like carbon (DLC) film is deposited. Since this DLC film has a large hardness, it is utilized as diaphragms of loud speakers and coatings of ornaments.
With increase in deposition target object temperature, the carbon film has a larger hardness. Therefore, in the case where carbon films are used as coatings for improving, e.g., a surface hardness of cutting tools, various kinds of machine parts or the like, the deposition temperature is generally set to 500° C. or more. If the deposition temperature is set to 900° C. or more, a diamond film is deposited.
As already described, however, the plasma CVD methods and apparatuses, which produce the plasma from the material gas by applying thereto the steady or modulated RF power or by applying the steady or pulse-form DC. power, cannot perform the film deposition at a sufficiently low temperature, and the deposited film cannot have a sufficiently lar
Doi Akira
Izumi Yoshihiro
Kuwahara Hajime
Nakahigashi Takahiro
Arent Fox Kintner Plotkin & Kahn
Chen Bret
Nissin Electric Co. Ltd.
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