JP2001026878A - Thin film forming device and formation of semiconductor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage caused by ions and to uniformly form a film on a large area by providing an electrode in which plural strip-type cathodes and anodes are alternately arranged in such a manner that they hold plasma forming regions therebetween on a substrate. SOLUTION: On a substrate 10, plural strip-type anode parts 1 and cathode parts 2 are alternately arranged in such a manner that they hold the forming regions of plasma 20 therebetween, the potential of the anode parts 1 is made into the grounded one, and the cathode parts 2 are connected to a high frequency power source 3. In this way, the plasma 20 is formed on the space between the anodes 1 and the cathodes 2, so that the region in which strong plasma is generated and the substrate 10 can spatially separated, and the direct exposure of the film growing face in the substrate 10 to the plasma 20 is suppressed. Therefore, damage caused by plasma ions subjected to the film growing face in the substrate 10 is reduced, and a semiconductor thin film of high quality can be formed. Moreover, the increase of power for generating plasma is made possible, and the film forming rate can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming apparatus and a method for forming a semiconductor thin film, and more particularly, to a thin film forming apparatus for forming a thin film on a substrate by a plasma CVD (Chemical Vapor Deposition) method and a thin film forming apparatus. The present invention relates to a method for forming a semiconductor thin film used.

[0002]

2. Description of the Related Art A plasma CVD method is a method in which a reactive gas is activated by exposing it to a plasma discharge and supplied to a substrate, and a desired thin film is formed by a chemical reaction on the substrate surface. This method is widely used for forming a semiconductor device because a thin film can be formed.

A high frequency plasma CVD apparatus using a plasma CVD method generally has a parallel plate type high frequency (RF) electrode 101 as shown in FIG. Specifically, a conventional high-frequency plasma CVD apparatus is:
It mainly has a reaction chamber 105, a high-frequency electrode 101 and a heater plate 104 which are arranged in the reaction chamber 105 so as to face each other. The high-frequency electrode 101 is a parallel-plate cathode and is electrically connected to a high-frequency power supply 103. The heater plate 104 is an anode that is set to the ground potential, and has a role of mounting the substrate 110 thereon and heating the substrate 110.

[0004] Film formation in this high-frequency plasma CVD apparatus is performed as follows. First, a reaction gas is introduced by a gas introduction system (not shown) such that the reaction chamber 105 has a constant gas pressure while the reaction chamber 105 is evacuated by a vacuum exhaust system (not shown). When a high-frequency voltage is applied to the electrode 101 by the high-frequency power supply 103 and the heater plate 104 is set to the ground potential, plasma 120 is generated, and a film is formed on the substrate 110 heated to a predetermined temperature by the heater plate 104. You.

[0005] On the other hand, a plasma CVD apparatus having an anode electrode and a cathode electrode arranged on a substrate is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-261481. An example of the plasma CVD apparatus disclosed in this publication includes a sample chamber 205 and three plasma generation chambers 206 as shown in FIG.
a, 206b and 206c, and counter electrodes 201 and 202 for plasma generation arranged in each plasma generation chamber. Plasma generation chambers 206a, 206b, 2
06c for forming a p-layer of a photoelectric conversion layer of a solar cell;
This is for generating gas plasma for forming an i-layer and for forming an n-layer.

[0006]

When a parallel plate type high frequency electrode 101 as shown in FIG. 4 is used, a plasma 120 is formed between the electrode 101 and the substrate 110, and the substrate 1
The ten film growth surfaces will be directly exposed to the plasma 120. For this reason, there is a problem that the film growth surface of the substrate 110 cannot avoid damage due to ions, and a high-quality semiconductor thin film cannot be obtained.

In addition, there is another problem that in order to form a film with high quality and uniformity, there are restrictions on combinations of various conditions such as a gas flow rate, a pressure, and a discharge power.

In the plasma CVD apparatus shown in FIG.
There is a problem that it is difficult to form a uniform film on the surface of the large-area substrate 210 because the counter electrodes 201 and 202 are separated by the plasma generation chamber.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thin film forming apparatus and a method of forming a semiconductor thin film which can prevent damage due to ions and can easily form a uniform film over a large area.

[0010]

A thin film forming apparatus according to the present invention is an apparatus for forming a thin film on the surface of a substrate by a plasma CVD method, wherein a plurality of strip-shaped cathode portions and anode portions are formed on the substrate. Have electrodes that are arranged alternately with the plasma forming region interposed therebetween.

In the thin film forming apparatus of the present invention, the cathode and the anode are alternately arranged on the substrate, so that the plasma is mainly formed between the cathode and the anode. Therefore, the region where the strong plasma is generated can be spatially separated from the substrate, and the film growth surface of the substrate can be suppressed from being directly exposed to the plasma. Therefore, plasma ion damage to the film growth surface of the substrate can be reduced, and a high-quality semiconductor thin film can be formed.

Further, even if the power for plasma generation is increased, the plasma ion damage on the film growth surface can be suppressed to a small level, so that the power for plasma generation can be increased. For this reason, a thin film having the same quality as that of the related art can be obtained at a high deposition rate.

Further, by alternately arranging a plurality of cathode portions and anode portions across the plasma forming region, uniform film formation can be easily performed on a large-area substrate surface. For this reason, the thin film forming apparatus of the present invention is suitable for the production of large-area display devices such as thin film transistors and photoelectric conversion devices such as solar cells.

Preferably, in the above-mentioned thin film forming apparatus,
The ratio of the distance between the tip of the electrode on the substrate side and the surface of the substrate to the average distance between the cathode and the anode adjacent to each other is 2
That is all.

Thus, plasma damage on the film growth surface of the substrate can be further reduced.

In the above thin film forming apparatus, preferably,
The distance between the cathode and the anode adjacent to each other increases as approaching the substrate.

Normally, strong plasma is generated in a portion where the distance between the cathode and the anode is short. For this reason, the region where strong plasma is generated can be kept away from the substrate surface by shortening the distance between the cathode portion and the anode portion as the distance from the substrate increases. Therefore, plasma ion damage on the film growth surface of the substrate can be further reduced, and a higher quality thin film can be formed or a higher speed film can be formed.

A method of forming a semiconductor thin film according to the present invention is a method of forming a semiconductor thin film using any one of the above-described thin film forming apparatuses.

Thus, a high-quality thin film can be formed or a high-speed thin film can be formed. In the method of forming a semiconductor thin film described above, preferably, any of a non-single-crystal silicon-based thin film and a non-single-crystal silicon-based alloy thin film is formed as the semiconductor thin film.

Accordingly, a non-single-crystal silicon-based thin film or a non-single-crystal silicon-based alloy thin film can be formed with high quality or high-speed film formation.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic sectional view showing a configuration of a high-frequency plasma CVD apparatus according to Embodiment 1 of the present invention. Referring to FIG. 1, the high-frequency plasma CVD apparatus according to the present embodiment mainly includes an anode unit 1, a cathode unit 2, a heater plate 4, and a reaction chamber 5.

A heater plate 4 is arranged in the reaction chamber 5. The heater plate 4 can place the substrate 10 thereon and plays a role of heating the substrate 10. The heater plate 4 is set to the ground potential. A plurality of anode units 1 and cathode units 2 are alternately arranged on the substrate 10 with the plasma forming region 20 interposed therebetween. The anode section 1 and the cathode section 2 have a strip shape as shown in FIG. The anode unit 1 is set to a ground potential, and the cathode unit 2 is electrically connected to a high-frequency power supply 3.

In FIG. 1, the vacuum evacuation system and the gas introduction system of the reaction chamber 5 are not shown for convenience of explanation.

Film formation in the high-frequency plasma CVD apparatus of the present embodiment is performed as follows.

First, while the reaction chamber 5 is evacuated by the vacuum exhaust system, a reaction gas is introduced by the gas introduction system so that the reaction chamber 5 has a constant gas pressure. The plurality of anodes 1 are set to the ground potential, and the plurality of cathodes 2 are
Is applied with a high-frequency voltage. As a result, plasma 20 is generated between the anode part 1 and the cathode part 2, and a film is formed on the substrate 10 heated to a predetermined temperature by the heater plate 4 (ground potential).

In this embodiment, since the anode portions 1 and the cathode portions 2 are alternately arranged on the substrate 10, the plasma 20 is mainly formed between the anode portion 1 and the cathode portion 2. For this reason, the region where the strong plasma is generated can be spatially separated from the substrate 10, and the film growth surface of the substrate 10 can be suppressed from being directly exposed to the plasma. Therefore, plasma ion damage to the film growth surface of the substrate 10 is reduced, and a high-quality semiconductor thin film can be formed.

Further, even if the power of plasma generation is increased, plasma ion damage on the film growth surface can be reduced.
The power of plasma generation can be increased. For this reason, a thin film having the same quality as that of the related art can be obtained at a high deposition rate.

Further, by alternately arranging a plurality of anode portions 1 and cathode portions 2, a uniform thin film can be easily formed on a large-area substrate surface. For this reason, the high-frequency plasma CVD apparatus of this embodiment is suitable for producing a large-area display device such as a thin film transistor, or a photoelectric conversion device such as a solar cell.

It is preferable that the ratio of the distance d _es between the adjoining anode part 1 and the cathode part 2 to the distance _des between the front ends of the electrodes 1 and 2 on the substrate side and the surface of the substrate 10 is 2 or more. .

Thus, the distance between the film growth surface of the substrate 10 and the plasma 20 can be set appropriately, so that plasma ion damage on the film growth surface of the substrate 10 can be further reduced.

(Embodiment 2) FIG. 3 is a sectional view schematically showing a configuration of a high-frequency plasma CVD apparatus according to Embodiment 2 of the present invention.

Referring to FIG. 3, in the present embodiment, the sectional shapes of anode portion 1 and cathode portion 2 are different from the configuration of the first embodiment. The cross-sectional shapes of the anode section 1 and the cathode section 2 of the present embodiment are both wedge-shaped.
Therefore, the distance between the anode portion 1 and the cathode 2 is widest spacing d _ca2 of the substrate 10 side tip (lower end in the drawing), the narrower enough away from the substrate 10, the narrowest spacing d _ca1 of the upper end in FIG. .

The remaining structure is almost the same as that of the first embodiment described above, so that the same members are denoted by the same reference numerals and description thereof will be omitted.

Generally, as the distance between the anode part 1 and the cathode part 2 is shorter, stronger plasma is generated. In the present embodiment, the distance between the anode unit 1 and the cathode unit 2 decreases as the distance from the substrate 10 increases, so that a region where strong plasma is generated can be kept away from the surface of the substrate 10.
Therefore, plasma ion damage on the film growth surface of the substrate 10 can be further reduced, and a film can be formed at a higher speed.

In this embodiment, the ratio of the distance _des between the tip of the electrodes 1 and 2 on the substrate 10 side and the surface of the substrate 10 to the average distance _dca between the adjacent anode part 1 and cathode part 2 is described. Is preferably 2 or more.

Thus, plasma ion damage on the film growth surface of the substrate 10 can be further reduced.

By forming a semiconductor thin film using the high-frequency plasma CVD apparatus according to the first and second embodiments, a high-quality semiconductor thin film can be formed or a high film forming rate can be realized.

Further, a non-single-crystal silicon-based thin film or a non-single-crystal silicon-based alloy thin film can be formed as a semiconductor thin film by this high-frequency plasma CVD apparatus, whereby a high-quality film can be manufactured. Note that in this specification, the term “non-single crystal” means a state including “polycrystalline”, “microcrystalline”, and “amorphous”.

As the non-single-crystal silicon-based thin film or non-single-crystal silicon-based alloy thin film, for example, a thin film or alloy thin film containing a Group 4 element can be formed.

[0041]

Embodiments of the present invention will be described below.

(Embodiment 1) The high-frequency plasma C shown in FIG.
Amorphous (amorphous) silicon film using VD equipment
Formed. Average distance d between strip electrodes_ca10 mm, electrode
D between the substrate and the substrate _esIs 15 mm, and d_es/ D_ca= 1.
It was set to 5. The source gas is SiH_FourAnd the reaction chamber pressure
Was set to 5.0 Torr. Also applied to the cathode section
Discharge power density of 50 mW / cm^TwoAt 200 ° C
Form amorphous silicon film on heated glass substrate
did.

As a result, the maximum film forming rate was 36 nm / min near the cathode portion, and the minimum film forming speed was 25 nm / min near the anode portion, resulting in a non-uniform film having uneven thickness. However, a film having high photosensitivity with a local ratio of photoconductivity σph / dark conductivity σd of 2 × 10 ⁶ was obtained.

The photoconductivity σph is AM 1.5, 1
The conductivity when the film was irradiated with light from a solar simulator of 00 mA / cm ² .

Example 2 Similarly, an amorphous silicon film was formed using the high frequency plasma CVD apparatus shown in FIG. 5mm average spacing d _ca of strip electrodes, the distance d _es between the electrode and the substrate and 15 mm, and a d _es / d _ca = 3.
SiH ₄ was used as a source gas, and the pressure in the reaction chamber was 5.0 T
orr. Further, an amorphous silicon film was formed on a glass substrate heated to 200 ° C. with a discharge power density applied to the cathode part being 50 mW / cm ² .

As a result, a high-quality film having high photosensitivity with a ratio of photoconductivity σph / dark conductivity σd of 2 × 10 ⁶ was obtained at a deposition rate of 40 nm / min.

Comparative Example 1 An amorphous silicon film was formed by using a conventional parallel plate type high frequency plasma CVD apparatus shown in FIG. The distance _des between the electrode and the substrate is 15 mm
And The source gas was SiH _4, and the pressure in the reaction chamber was 5.0 Torr. Further, an amorphous silicon film was formed on a glass substrate heated to 200 ° C. with a discharge power density applied to the cathode part being 50 mW / cm ² .

[0048] As a result, it became photoconductivity Shigumaph / dark conductivity σd = 3 × 10 ⁴ low light sensitivity of the low-quality film at a deposition rate of 34 nm / min.

Comparative Example 2 An amorphous silicon film was formed using the conventional parallel plate type high frequency plasma CVD apparatus shown in FIG. The distance _des between the electrode and the substrate is 1
5 mm. The source gas was SiH _4, and the pressure in the reaction chamber was 5.0 Torr. Further, the discharge power density applied to the cathode portion was set to 10 mW / cm ² , and
An amorphous silicon film was formed on a glass substrate heated to 0 ° C.

As a result, the photoconductivity σph / dark conductivity σd
Was 3 × 10 ^{6, and} a high quality film having good photosensitivity was obtained, but only a low film formation rate of 8 nm / min was obtained.

(Embodiment 3) The high-frequency plasma C shown in FIG.
An amorphous silicon film was formed using a VD apparatus.
The cross-sectional shape of the strip electrode is a wedge shape as shown in FIG. 3, the shortest distance d _ca1 between the cathode and the anode is 3 mm, the longest distance d _ca2 is 7 mm, and the average interval d _ca is 5 mm.
The distance _des between the electrode and the substrate is 15 mm, and _des / _dca =
It was set to 3. When an electrode having this shape is used, the region between the cathode and anode, where the distance between the cathode and the anode is short and where a strong plasma is generated, is farther from the film growth surface than in FIG. 1, so that plasma ion damage can be further reduced and high-speed formation can be achieved. A membrane has become possible. SiH ₄ was used as a source gas, and the pressure in the reaction chamber was set to 5.0 Torr. Further, an amorphous silicon film was formed on a glass substrate heated to 200 ° C. with a discharge power density applied to the cathode portion being 100 mW / cm ² .

As a result, a high-quality film having high photosensitivity with a ratio of photoconductivity σph / dark conductivity σd of 1 × 10 ⁶ was obtained at a film forming rate of 68 nm / min.

The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0054]

As described above, according to the present invention, since the cathode portions and the anode portions are alternately arranged on the substrate, the region where strong plasma is generated can be spatially separated from the substrate. Direct exposure of the film growth surface of the substrate to the plasma can be suppressed. Therefore, plasma damage to the film growth surface of the substrate is reduced, and a high-quality semiconductor thin film can be formed.

Further, even if the power for plasma generation is increased, the plasma damage on the film growth surface can be reduced, so that the power for plasma generation can be increased and a thin film of the same quality as the conventional one can be obtained at a high deposition rate. it can.

Further, by alternately arranging a plurality of cathode portions and anode portions, a uniform thin film can be easily formed on a large-area substrate surface. For this reason, the thin film forming apparatus of the present invention is suitable for the production of large-area display devices such as thin film transistors and photoelectric conversion devices such as solar cells.

According to the method for forming a semiconductor thin film using the thin film forming apparatus of the present invention, a high quality thin film can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a high-frequency plasma CVD apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view showing that an anode part and a cathode part are strip-shaped.

FIG. 3 is a sectional view schematically showing a configuration of a high-frequency plasma CVD apparatus according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically showing a configuration of a conventional high-frequency plasma CVD apparatus.

FIG. 5 is a cross-sectional view schematically showing a configuration of a plasma CVD apparatus disclosed in the official gazette.

[Explanation of symbols]

1 Anode unit, 2 cathode unit, 3 high frequency power supply, 4
Heater plate, 5 reaction chambers, 20 plasmas.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 BA30 BB04 BB05 FA03 JA03 KA15 KA30 5F045 AA08 AB03 AB04 AC01 AD06 AE21 AF07 BB09 BB16 DA65 EH04 EH12 EK07

Claims (5)

[Claims] 1. An apparatus for forming a thin film on a substrate surface by a plasma CVD method, wherein a plurality of strip-shaped cathode portions and anode portions are alternately arranged on the substrate with a plasma formation region interposed therebetween. A thin film forming apparatus having an electrode having a configuration as described above. 2. The thin film according to claim 1, wherein a ratio of an interval between the tip of the electrode on the substrate side and the surface of the substrate to an average interval between the cathode and the anode adjacent to each other is 2 or more. Forming equipment. 3. The thin film forming apparatus according to claim 1, wherein an interval between the cathode portion and the anode portion adjacent to each other increases as approaching the substrate. 4. A method for forming a semiconductor thin film using the thin film forming apparatus according to claim 1. 5. The method according to claim 4, wherein one of a non-single-crystal silicon-based thin film and a non-single-crystal silicon-based alloy thin film is formed as the semiconductor thin film.