JP2001089863A - Plasma cvd device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma CVD device capable of increasing the reproducibility and uniformity of a film deposition process. SOLUTION: This system is provided with a film deposition unit in which reactive gas is introduced, a heater for heating a substrate under its holding in the film deposition unit, an electrode arranged oppositely to the substrate held in the heater unit, a high-frequency power source feeding high-frequency to the electrode for generating plasma between the electrode and the substrate and a low resistance member for reducing impedance from the heater unit in the process of generating plasma to the film deposition unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a plasma CVD apparatus used for manufacturing a solar cell.

[0002]

2. Description of the Related Art As shown in FIG.
Supplies a reactive gas from the gas supply mechanism 6 while heating the substrate 3 by the heater 2 and applies a high frequency to the electrode 5 to generate plasma between the electrode 5 and the substrate 3;
A film is formed on the substrate 3. For example, a high frequency of 13.56 MHz is applied to the electrode 5.

[0003] Recently, attempts have been made to increase the film forming speed and improve the film quality by applying a higher frequency to the electrodes to increase the plasma density.

[0004]

However, the conventional heater 2 has a variety of attached parts such as a heater cover, a vacuum bellows, a heat equalizing plate, a cooling pipe, an eye plate, and a hanging metal fitting. Even if it is DC grounded, a floating potential V is generated between the heater body / heater cover or between the heater body / film forming unit when a high frequency such as 24 MHz is applied.
When the floating potential V is generated, the generated plasma becomes unstable, and the reproducibility and uniformity of the film forming process are impaired, which causes a problem that the product yield is reduced.

The present invention has been made to solve the above-mentioned problems, and has as its object to provide a plasma CVD apparatus capable of improving the reproducibility and uniformity of a film forming process.

[0006]

Means for Solving the Problems Plasma C according to the present invention
The VD apparatus is a plasma C that heats the substrate during the formation of a film on the substrate by causing a reactive gas to decompose and react with the generated plasma.
In the VD apparatus, a film forming unit into which a reactive gas is introduced, a heater unit for holding and heating a substrate in the film forming unit, an electrode arranged to face the substrate held by the heater unit, A high-frequency power supply that supplies high-frequency power to electrodes to generate plasma between the substrate and the substrate, and a low-resistance member that reduces impedance from the heater unit to the film forming unit during plasma generation. Features.

Preferably, the low resistance member is provided inside the heater unit. In this case, the heater unit includes a heater body that generates resistance heat, and a heater cover that covers at least the substrate mounting surface of the heater body, and the low-resistance member is disposed between the heater body and the heater cover. Preferably, it is inserted.

Preferably, the low resistance member is provided between the heater unit and the film forming unit. In this case, the heater unit is preferably made of a resistance heating element that is not covered by the cover.

It is preferable to use a material excellent in electric conductivity such as industrially pure pure copper, pure aluminum, pure silver or a silver alloy for the low resistance member. In this case, the low resistance member needs to be a material having a small contact resistance with at least the materials of the heater unit and the film forming unit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) Plasma CVD Apparatus 1
A is, for example, austenitic stainless steel (SUS30
Film forming units 1a and 1b made of a heat-resistant alloy as in 4)
It has. The film forming units 1a and 1b are separated by a seal ring 13, and the film forming unit 1a serving as a processing chamber is evacuated by a vacuum pump via an exhaust passage (not shown). Also, the film forming unit 1
The outlet of the gas supply mechanism 6 communicates with the inside of a, and a process gas containing silane as a main component is supplied from a supply source (not shown) toward the substrate 3 in the film forming unit 1a. .

The film forming unit 1a has a heater unit 2A for heating the glass substrate 3 to a predetermined target temperature. The heater unit 2A may be of a double-sided heating type.
Is held. Each substrate 3 is pressed and held against a heating surface of the heater unit 2A by, for example, a positioner (not shown).

The heater unit 2A includes a heater main body 2a made of a resistance heating element and a heater cover 2b covering the same. The heater main body 2a has a vacuum bellows 13 for absorbing thermal expansion. The vacuum bellows 13 is provided in the film forming unit 1b as a heater introduction part. A seal ring 13 is inserted between the vacuum bellows 13 and the film forming unit 1b, whereby the film forming processing space is shut off from the external space. In addition, the seal ring 1
Numeral 3 is made of rubber, and the heater unit 2A and the film forming units 1a and 1b are insulated from each other. The film forming units 1a and 1b and the heater unit 2A are grounded.

The heater cover 2b is made of a heat-resistant alloy such as austenitic stainless steel (SUS316), on which the substrate 3 is placed and held. The heater cover 2b covers at least the main surface of the heater main body 2a and protects the heater main body 2a from plasma.

As shown in FIG. 1, a copper plate 14 as a low resistance member is inserted between the heater main body 2a and the heater cover 2b. The copper plate 14 is almost the same size as the main surface of the heater main body 2a, and has a high electrical conductivity made of industrially pure copper. By providing such a low resistance member 14, the impedance Zx between the heater body 2a and the heater cover 2b is reduced.

A ladder electrode 5 of a multi-terminal power supply system is disposed facing the substrate 3 on the heater unit 2A. The ladder electrode 5 is formed of a parallel-lattice metal wire grid, and is connected to the high-frequency power supply 8 via a plurality of terminals. A matching device (not shown) is provided between the ladder electrode 5 and the high-frequency power supply 8 so that the power supply operation is subjected to matching control so that plasma is reliably and stably generated. The high-frequency power supply 8 applies high-frequency power (voltage) having a frequency of 24 MHz to the electrode 5.

Further, a gas supply mechanism 6 is arranged on the back side of the electrode 5, and further, a deposition preventing plate 7 is arranged on the back side of the gas supply mechanism 6. The piping of the gas supply mechanism 6 is connected to a gas supply source (not shown) so that a process gas containing silane as a main component is supplied as a reactive gas.

The distance between the substrate 3 and the electrode 5 is set to, for example, about 35 mm, and the distance between the substrate 3 and the gas supply mechanism 6 is set to, for example, 40 to 90 mm. Plasma is generated in a narrow area sandwiched between the substrate 3 and the electrode 5. A radical heater 4 is provided in this plasma generation region, and heats the surface (film-forming surface) of the substrate 3 to a desired temperature during plasma generation.

As shown in FIG. 2, the electrode 5 and the heater main body 2a are electrically connected via the generated plasma, and a circuit is formed. The impedance of this circuit corresponds to the sum of the impedance Zp of the generated plasma and the impedance Zx between the heater body and the heater cover.

An amorphous silicon film (a-Si film) is actually formed on the substrate 3 under the following conditions by using the plasma CVD apparatus 1A of the present embodiment, and the obtained a-Si film has a uniform thickness. Was evaluated.

The substrate 3 to be processed is 500 mm × 500 m
An m-size glass substrate was tested. Pure silane gas was used as a raw material process gas. The internal pressure of the film forming unit 1a was set to 0.1 Torr.

In the apparatus 1A of this embodiment, since the low-resistance member 14 made of a copper plate is inserted between the heater main body and the heater cover, the impedance Zx therebetween is greatly reduced, and as a result, a high frequency of a high frequency of 24 MHz is obtained. , The floating potential V is applied to the heater unit 2A.
Was found to no longer occur. As a result, a-Si
It was confirmed that the film thickness uniformity was improved as compared with the conventional case.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the description of the parts of this embodiment that overlap with the first embodiment will be omitted.

The plasma CVD apparatus 1B of the second embodiment
Has a heater unit 2B without a heater cover. That is, the heater unit 2B itself is formed of a planar resistance heating element that generates resistance.

As shown in FIG. 3, a copper sleeve 24 as a low resistance member is provided with a film forming unit 1b as a heater introduction portion.
And the vacuum bellows 12 on the heater unit 2B side. The copper sleeve 24 has a ring shape and is made of industrially pure copper and has a high electric conductivity. By providing such a low resistance member 24, the impedance Zy between the heater unit 2B and the film forming units 1a and 1b is reduced.

A ladder electrode 5 of a multi-terminal power supply system is arranged facing the substrate 3 on the heater unit 2B. The ladder electrode 5 is formed of a parallel-lattice metal wire grid, and is connected to the high-frequency power supply 8 via a plurality of terminals. A matching device (not shown) is provided between the ladder electrode 5 and the high-frequency power supply 8 so that the power supply operation is subjected to matching control so that plasma is reliably and stably generated. The high-frequency power supply 8 applies high-frequency power (voltage) having a frequency of 60 MHz to the electrode 5.

As shown in FIG. 4, the electrode 5 and the heater unit 2B are electrically connected via the generated plasma, and the heater unit 2B and the chamber wall of the film forming unit 1b are electrically connected. Is formed. The impedance of this circuit corresponds to the sum of the impedance Zp of the generated plasma and the impedance Zy between the heater unit and the film forming unit. In the apparatus of the present embodiment, since the low resistance member 24 is provided between the heater unit and the film forming unit, the impedance Zy therebetween is reduced, so that even if a high frequency of a high frequency of 60 MHz is used, the heater unit / film forming unit is used. No floating potential V is generated between the units.

An amorphous silicon film (a-Si film) is actually formed on the substrate 3 under the following conditions using the plasma CVD apparatus 1B of the present embodiment, and the resulting a-Si film has a uniform thickness. Was evaluated.

The substrate 3 to be processed is 500 mm × 500 m
An m-size glass substrate was tested. Pure silane gas was used as a raw material process gas. The internal pressure of the film forming unit 1a was set to 0.1 Torr.

In the apparatus 1B of the present embodiment, since the low resistance member 24 made of a copper sleeve ring is inserted between the heater unit and the film forming unit, the impedance Zy between the low resistance member 24 and the low resistance member 24 is greatly reduced. It has been found that the floating potential V does not occur between the heater unit and the film forming unit even when a high frequency is used. As a result, it was confirmed that the film thickness uniformity of the a-Si film was improved as compared with the related art.

In the above embodiment, 500 mm × 50
Although the case where a film is formed on a substrate having a size of 0 mm has been described, the present invention is not limited thereto.
It is also possible to form a film on a large substrate having a size of 0 mm × 1000 mm.

[0032]

As described above in detail, according to the present invention, a low resistance member having high electric conductivity is provided between the heater body / heater cover or between the heater unit / film forming unit. The impedance between them is greatly reduced. Therefore, even if a high frequency of a high frequency is used, the floating potential V is not generated, the generated plasma is stabilized, the reproducibility and uniformity of the film forming process are improved, and as a result, the film thickness uniformity is remarkably improved. Was.

[Brief description of the drawings]

FIG. 1 is a plasma CVD according to a first embodiment of the present invention.
FIG. 2 is a block sectional view showing the device.

FIG. 2 is a circuit diagram schematically illustrating electrical characteristics of the plasma CVD apparatus according to the first embodiment.

FIG. 3 shows a plasma CVD according to a second embodiment of the present invention.
FIG. 2 is a block sectional view showing the device.

FIG. 4 is a circuit diagram schematically illustrating electrical characteristics of a plasma CVD apparatus according to a second embodiment.

FIG. 5 is a perspective view showing an outline of a plasma CVD apparatus.

[Explanation of symbols]

1, 1A, 1B: plasma CVD apparatus, 1a, 1b: film forming unit, 2, 2A, 2B: heater unit, 2a ...
Heater body, 2b heater cover, 3 substrate, 4 radical heater (heater for substrate surface heating), 5 electrode, 6 ...
Gas supply mechanism, 7: anti-adhesion plate, 8: high frequency power supply, 12: vacuum bellows, 13: seal ring, 14, 24: low resistance member.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsufumi Aoi 1-1, Akunouracho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Eishiro Sasakawa 1-1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Inside Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Kazuhiko Ogawa 1-1, Akunouramachi, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard F-term (reference) 4K030 AA06 BA30 CA06 FA03 FA10 KA14 KA23 KA45 KA46 5F045 AA08 AB04 AC01 AE19 AF07 BB02 CA13 EH04 EH12 EH19 EK07 EK08 5F051 BA14 CA16 CA23 CA24

Claims (5)

[Claims] 1. A plasma CVD apparatus for heating a substrate while a reactive gas is decomposed by a generated plasma to form a film on a substrate, wherein the reactive gas is introduced into the film forming unit; A heater unit that holds and heats the substrate with the electrode, an electrode that faces the substrate held by the heater unit, and a high-frequency power supply that supplies a high frequency to the electrode to generate plasma between the electrode and the substrate. A low-resistance member that reduces impedance from the heater unit to the film forming unit during plasma generation;
A plasma CVD apparatus comprising: 2. The plasma CVD apparatus according to claim 1, wherein said low resistance member is provided inside said heater unit. 3. The heater unit includes: a heater body that generates resistance heat; and a heater cover that covers at least a substrate mounting surface of the heater body, wherein the low-resistance member includes the heater body and the heater cover. 3. The plasma CVD apparatus according to claim 2, wherein the apparatus is inserted between the two. 4. The plasma CVD apparatus according to claim 1, wherein said low resistance member is provided between said heater unit and said film forming unit. 5. The plasma CVD apparatus according to claim 4, wherein said heater unit comprises a resistance heating element not covered by a cover.