JPH06224132A - Plasma chemical vapor deposition apparatus - Google Patents

Abstract

PURPOSE:To obtain a plasma CVD apparatus wherein a film can be quickly and uniformly formed on a large substrate. CONSTITUTION:A plasma CVD apparatus is equipped with a reaction vessel 1, a reactive gas feed/exhaust means connected to the reaction vessel 1, a pair of electrodes provided inside the reaction vessel, a substrate holder provided between the electrodes, and a high frequency power supply 13 connected to the electrodes, wherein one of the electrodes is a flat plate-type electrode, and the other is a continuous plate electrode composed of electrodes 2-a to 2-d arranged in a row at a prescribed variable interval.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma chemical vapor deposition (plasma CVD) apparatus suitable for the production of large area thin films used in various electronic devices such as amorphous silicon solar cells, thin film semiconductors, and semiconductor protective films for photosensors. .

[0002]

2. Description of the Related Art Conventionally, plasma CVD has been used to manufacture a large-area amorphous silicon thin film.
The configuration of the device will be described with reference to FIG. This technical means is known as disclosed in, for example, Japanese Patent Application No. 61-106314.

In the reaction vessel 1, electrodes 2 and 3 for generating glow discharge plasma are arranged in parallel.
These electrodes 2 and 3 are connected to, for example, 60
Power of commercial frequency of Hz is supplied. A DC power supply or a high frequency power supply can be used as the power supply. A coil 5 is wound around the reaction container 1 so as to surround the reaction container 1, and AC power is supplied from an AC power supply 6. In the reaction container 1, a reaction gas introducing pipe 7 is supplied from a cylinder (not shown).
Through, a mixed gas of, for example, monosilane and argon is supplied. The gas in the reaction container 1 is exhausted by the vacuum pump 9 through the exhaust pipe 8. The substrate 10 has electrodes 2 and 3
It is supported by an appropriate means outside the discharge space formed by so as to be orthogonal to the surfaces of the electrodes 2 and 3.

Using this apparatus, a thin film is manufactured as follows. The vacuum pump 9 is driven to exhaust the inside of the reaction container 1. When a mixed gas of, for example, monosilane and argon is supplied through the reaction gas introducing pipe 7, the pressure in the reaction container 1 is maintained at 0.05 to 0.5 Torr, and a voltage is applied from the low frequency power supply 4 to the electrodes 2 and 3. , Glow discharge plasma is generated. An AC voltage of 100 Hz, for example, is applied to the coil 5 to generate a magnetic field B in a direction orthogonal to the electric field E generated between the electrodes 2 and 3. The magnetic flux density in this magnetic field is 10
Gauss is enough.

Of the gas supplied from the reaction gas introducing pipe 7, monosilane gas is decomposed by glow discharge plasma generated between the electrodes 2 and 3. As a result, radicals Si are generated and adhere to the surface of the substrate 10 to form a thin film.

[0006] Charged particles such as argon ions are stored in the electrode.
Coulomb force F due to electric field E between 2 and 3 ₁= QE and low
Lenz force F₂= Q (V · B) (where V is the charged particle
(Velocity) causes a so-called EB drift motion.
You Charged particles are given an initial velocity by EB drift.
In the state of
Fly towards 10. However, it occurs between electrodes 2 and 3.
In the discharge space where the influence of the electric field generated by the
By the cyclotron motion by the magnetic field B generated,
or orbit and fly. Therefore, Argon
It is rare for charged particles such as on to hit the substrate 10 directly.
Yes.

The electrically neutral radicals Si are not affected by the magnetic field B, deviate from the orbits of the charged particle group and reach the substrate 10, and form an amorphous thin film on the surface thereof. Since the radicals Si collide with the charged particles flying in the Larmor orbit, an amorphous thin film is formed not only in front of the electrodes 2 and 3 but also in the left or right. Moreover, since the magnetic field B is changed by the AC power source 6, it is possible to uniformly form an amorphous thin film on the surface of the substrate 10.
It should be noted that the electrodes 2 and 3 can be made as long as the length of the reaction vessel 1 allows, so that there is no problem. Therefore, even if the substrate 10 is long, a uniform amorphous surface is formed on the surface thereof. It becomes possible to form a thin film.

[0008]

In the above-mentioned conventional apparatus, a magnetic field B is generated in a direction orthogonal to the discharge electric field E between the electrodes for generating glow discharge plasma, so that a large area film can be easily formed. It is possible. However, there are the following problems.

When forming a large-area film, it is necessary to use long electrodes. In order to generate stable plasma using a long electrode, it is easier for the frequency of the power source to be as low as possible.
A 00 Hz power supply is used. However, under the condition that the frequency becomes low and the ion migration distance during the half cycle exceeds the electrode interval, it was emitted from the cathode by ion collision to maintain the plasma, as in the case of DC discharge. Secondary electrons play an essential role. Therefore, if a film is attached to the electrodes and insulated, no electric discharge will occur at that portion. In this case, it is necessary to keep the electrode surface clean at all times. Therefore, complicated work such as frequent replacement of electrodes or frequent cleaning is required, which is one of the factors of high cost.

If a high frequency power source of 13.56 MHz, for example, is used as the plasma generation source in order to make up for the above-mentioned drawbacks, secondary electrons emitted from the electrode for sustaining the discharge are not essential, and insulation of a film or the like is not formed on the electrode. A glow discharge is formed between the electrodes even if there is an object. However, when a long electrode is used, most of the current flows on the surface (about 0.01 mm) due to the skin effect due to the high frequency, so that the electric resistance increases. For example, the length of the electrode is about 1
When it is more than m, a potential distribution appears on the electrode and uniform plasma is not generated. Considering this with a distributed constant circuit, it becomes as shown in FIG. In FIG. 9, x indicates the distance in the lengthwise direction of the electrode. That is, the resistance R per unit length of the electrode is the impedance Z _{1 of the} discharge portion,
When it becomes so large that it cannot be ignored compared to Z ₂ , ..., Z _n , a potential distribution appears in the electrode. Therefore, when a high frequency power source is used, the film thickness is significantly different between the central portion of the substrate and its peripheral portion. Therefore, it is very difficult to form a film on a large area, and it has not been practically possible so far.

According to the above method, 50 cm × 50 cm
When manufacturing the large-area amorphous silicon thin film described above, it was very difficult to maintain the film thickness distribution at ± 10% or less and the film forming rate at 1Å / sec or more.

[0012]

The present invention takes the following means in order to solve the above problems.

That is, the reaction container, the reaction gas supply / discharge means connected to the reaction container, the pair of electrodes provided in the reaction container, the substrate holder provided between the electrodes, and the electrode. In a plasma CVD apparatus having a connected high frequency power source, one of the pair of electrodes is a flat plate electrode and the other is a plurality of long plate electrodes arranged in a line at predetermined variable intervals.

[0014]

In the above means, the substrate to be CVD is set on the substrate holder in the reaction container. Then, the intervals between the plurality of long plate electrodes are optimally set according to the type of reaction gas, the flow rate, the pressure, and the discharge power. Thereafter, the reaction gas is supplied to and discharged from the high-frequency power source while a predetermined vacuum is applied to the inside of the reaction vessel by the reaction gas supply / exhaust means to supply glow discharge plasma between the electrodes. Then, the reaction gas is excited, the CVD action is accelerated, and a film is rapidly formed on the substrate.

In the above, since the high frequency power source is used for glow discharge, the glow discharge is easily generated and the insulator does not adhere to the electrodes. Further, by optimizing the distance between the long plate electrodes, the electric field distribution and the flow of the reaction gas are made uniform, and uniform vapor deposition can be obtained on a substrate having a large area.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

1 and 2, a reaction gas introducing pipe 7 is connected to one side of the reaction container 1. An exhaust pipe 8 having a vacuum pump is connected to the other side. At the center of the reaction vessel 1, a flat plate-shaped electrode 14 is arranged orthogonal to the gas flow. Power supply rod 15a orthogonal to the center of the plate electrode 14
One end of is attached. A plurality of long plate electrodes 2-a to 2-d are arranged in a line facing the flat plate electrode 14 with a predetermined space D therebetween. Each long plate electrode 2-a to 2-d is
It is attached to the stringer 15 so that the distance D can be changed at the center.

From the 13.56 MHz high frequency power source 13 through the impedance matching device 12, the power supply lines 16, 1
7 is connected to the stringer 15 and the power supply rod 15a. In the figure, 11 is an introduction terminal.

In the vicinity of the flat electrode 14, the substrate 10 to be CVD is set in parallel with the electrode surface by a substrate holder (not shown).

In the above, high frequency power is supplied from the high frequency power supply 13 to the flat plate electrode 14 and the plurality of long plate electrodes 2-a to 2-d through the impedance matching device 12.

On the other hand, for example, monosilane is supplied into the reaction vessel 1 from a reaction gas supply device (not shown) through the reaction gas introduction pipe 7. The gas in the reaction vessel 1 is the exhaust pipe 8
Through a vacuum pump 9.

Using this apparatus, a thin film is manufactured as follows. The vacuum pump 9 is driven to exhaust the inside of the reaction container 1. Monosilane, for example, is supplied at a flow rate of about 100 cc / min through the reaction gas introduction pipe 7, and the pressure in the reaction vessel 1 is maintained at 0.5 Torr, for example. Then, from the high frequency power supply 13 to the impedance matching device 12 and the power supply line 1
6, 17 and the like, a plurality of long plate electrodes 2-a, 2-
When electric power is supplied to b, 2-c, 2-d and the plate-shaped electrode 14 that is grounded, glow discharge plasma is generated between the electrodes. When glow discharge plasma is generated, the monosilane gas is decomposed, radical species are generated, and amorphous silicon (a-Si) is formed on the surface of the substrate 14.

At this time, depending on the size of the substrate 14, the power, the flow rate of the reaction gas, and the pressure, a plurality of long plate electrodes 2-a,
By optimally adjusting the distance D between 2-b, 2-c, and 2-d, the flow of the reaction gas and the electric field are made uniform, and a film is rapidly and uniformly formed on the substrate 14 having a large area. To be done.

The size of the substrate 10 should be slightly shorter than that of the plate electrode 14 (R = 20 to 50 mm in FIG. 1). The outermost diameter dimension of the long plate electrodes 2-a to 2-d is set to be substantially equal to the outer diameter dimension of the flat plate electrode 14. The width of each long plate electrode should be smaller than the distance between the flat plate electrode 14 and the long plate electrode.

An experimental example according to this embodiment will be described below. (A) Substrate-Substrate material: glass-Substrate temperature: 200 ° C-Substrate area: 20 cm x 20 cm (b) Reaction gas-Monosilane gas flow rate: 100 cc / min-Reaction vessel pressure: 0.05 to 0.15 Torr (c) Electrode・ Plate electrode: 40cm × 40cm ・ Distance between flat electrode and long plate electrode: 4cm ・ Length and width of long plate electrode: 40cm and 2cm respectively ・ Distance between long plate electrode: 0.5cm〜 5 cm High frequency power: 10 W to 100 W Frequency: 13.56 MHz Results of forming a film of amorphous silicon with the above configuration are shown in FIGS.

FIG. 3 is data showing the dependence of the thickness distribution of the formed a-Si film on the distance D between the long plate electrodes. Same as above If the distance between electrodes is adjusted optimally, the film thickness distribution will be ± 5.
It shows that it will be within%. The film thickness distribution ± 5%
The film formation rate was about 1Å / sec.

4 to 6 are data showing the dependence of the thickness distribution of the formed a-Si film on the high frequency power at the distance D = 25 mm between the long plate electrodes. a
It is shown that if the distance D between the long plate electrodes is adjusted to an optimum value according to the high frequency power used for forming the -Si film, the film thickness distribution is within ± 5%. The film thickness distribution of FIG. 6 ± 5%
The film forming rate was 3Å / sec.

In FIGS. 3 to 6, the fact that the film thickness distribution has the optimum value means that the flow of the reaction gas is caused by the flat plate electrode 14 and the long plate electrodes 2-a to 2- as shown in FIG. This is due to the non-uniformity between d and the existence or non-existence of the value of the high frequency power that decomposes the gas. That is, in FIG. 3, on the side longer than the distance between the long plate electrodes D = 25 mm, the amount of the reaction gas is large, so that the central portion of the substrate where the power supply amount is large becomes thick.

On the side shorter than D = 25 mm, the reaction gas amount is insufficient in the central portion of the substrate, so that the central portion of the substrate becomes thin.

In each of FIGS. 4 to 6, the central portion of the substrate becomes thin due to the shortage of the reaction gas on the side larger than the electric power value corresponding to the optimum film thickness distribution, and the reaction gas is smaller on the side smaller than the electric power value. Since the amount is large, the film thickness becomes thicker in the central portion of the substrate.

As is clear from the above experimental results, according to the apparatus of the present embodiment, according to the use condition, that is,
The distance between the long plate electrodes can be set to an optimum value in advance according to the flow rate / pressure of the reaction gas and the high frequency power, so that an a-Si film with a uniform film thickness distribution can be formed in a large area and under high speed film forming conditions. It is possible.

[0032]

As described above in detail, by using the plasma CVD apparatus of the present invention, it becomes possible to form a thin film uniformly and at high speed on a large area substrate. Therefore, the industrial value in the fields of amorphous silicon solar cells, thin film transistors, optical sensors, semiconductor protective films, etc. is extremely large.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a flat plate-shaped electrode and a plurality of long plate electrode parts of the embodiment.

FIG. 3 is an explanatory view of the operation of the embodiment.

FIG. 4 is an explanatory view of the operation of the embodiment.

FIG. 5 is an explanatory view of the operation of the embodiment.

FIG. 6 is an explanatory view of the operation of the embodiment.

FIG. 7 is an explanatory view of the operation of the embodiment.

FIG. 8 is a configuration diagram of a conventional example.

FIG. 9 is an explanatory view of the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2-a to 2-d Long plate electrode 7 Reaction gas introduction tube 9 Vacuum pump 10 Substrate 13 High frequency power supply 14 Flat plate (ground) electrode 15a Power supply rod

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daiichi Furushiro 5-717-1 Fukahori-cho, Nagasaki-shi Nagasaki Research Institute, Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A reaction vessel, a reaction gas supply / discharge means connected to the reaction vessel, a pair of electrodes provided in the reaction vessel, a substrate holder provided between the electrodes, and the electrode. In a plasma enhanced chemical vapor deposition apparatus having a high frequency power supply connected, one of the pair of electrodes is a flat plate-shaped electrode and the other is a plurality of long plate electrodes arranged in a line at a predetermined variable interval. Plasma chemical vapor deposition apparatus.