JPH0745540A - Chemical plasma evaporating device - Google Patents

Abstract

PURPOSE:To enable the amorphous silicon thin film capable of evenly sustaining the distribution of a reaction gas between electrodes as well as the film thickness distribution within a specific range to be manufactured. CONSTITUTION:A plasma producing electrode 101 opposing a grounding electrode 3 arranged in a reaction vessel 1 is provided with plural reaction gas leading-in ports 102 and after feeding the rear surface of the plasma producing electrode 102 with a reaction gas, the reaction gas can be efficienctly led into the space between the electrodes 3 and 101 by feeding the reaction gas to the space through the intermediary of the reaction gas leading-in ports 102. Furthermore, the reaction gas distribution can be made even so that the large area amorphous thin film can be rapidly formed by glow discharge plasma thereby enabling the title chemical plasma evaporating device having notably high industrial value in the manufacturing field of amorphous silicon solar cell, liquid crystal displaying thin film transistor and photoelectronic device, etc., to be realized.

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 apparatus (hereinafter referred to as plasma CVD) applied to the production of large-area thin films used in various electronic devices such as amorphous silicon solar cells, thin film transistors, photosensors, and semiconductor protective films.
With equipment).

[0002]

2. Description of the Related Art The structure of a conventional plasma CVD apparatus applied to manufacture a large-area amorphous silicon thin film will be described with reference to FIG. Regarding this, there is Japanese Patent Application No. 4-113336, which is a prior application of the present applicant.

In FIG. 9, an electrode 2 and a ground electrode 3 for generating glow discharge and plasma are provided in a reaction vessel 1.
Are arranged to face each other. Electric power having a frequency of, for example, 13.56 MHz is supplied to the electrode 2 from the high frequency power source 4.
It is supplied via the impedance matching circuit 5, the first high frequency cable 6 and the power introduction terminal 7. The ground electrode 3 is connected to the ground 9 via the reaction vessel 1 and the second high frequency cable 8. The ground side terminal of the impedance matching circuit 5 is the third high frequency cable 1
It is connected to the reaction container 1 by 0.

A reaction gas such as monosilane is supplied into the reaction vessel 1 from a cylinder (not shown) having a flow meter through a reaction gas introduction pipe 11, and the gas in the reaction vessel 1 is passed through an exhaust pipe 12 to a vacuum pump ( It is exhausted by (not shown). The substrate 13 is arranged parallel to the electrodes 2 and 3, that is, orthogonal to the electric field generated by the electrodes 2 and 3.

Around the reaction vessel 1, there are finite length solenoid coils 14a, 14b, 15 having first to fourth thicknesses.
a and 15b are arranged, the first and second solenoid coils 14a and 14b form a pair, and the third and fourth solenoid coils 15a and 15b form a pair, and their respective axes are orthogonal to each other. Direction, ie x-axis direction and y
It is arranged to match the axial direction.

The above first and second solenoid coils 14
A sinusoidal waveform of electric power is supplied to a and 14b from one output terminal of the variable phase two-output oscillator 16 via the first power amplifier 17. Further, the third and fourth solenoid coils 15a and 15b are supplied with sinusoidal power from the other output terminal of the phase variable two-output oscillator 16 via the second power amplifier 18.

The phase variable two-output oscillator 16 can output two sine wave signals with their relative phases arbitrarily set, and outputs the first and second solenoid coils 1.
4a, 14b and third and fourth solenoid coils 1
The magnetic fields generated by 5a and 15b have a substantially uniform strength distribution in the axial direction.

Next, the production of a thin film using the above apparatus will be described below. First, the inside of the reaction container 1 is evacuated by driving a vacuum pump (not shown). After that, for example, a mixed gas of monosilane and hydrogen is supplied through the reaction gas introduction pipe 11 to adjust the pressure in the reaction vessel 1 to 0.05 to
While maintaining at 0.5 Torr, a voltage is applied from the high frequency power source 4 to the electrodes 2 and 3, and glow discharge plasma is generated between the electrodes 2 and 3.

On the other hand, the first and second solenoid coils 1
4a, 14b and third and fourth solenoid coils 1
2a from the phase variable 2-output oscillator 16 are connected to 5a and 15b.
Apply output. This is, for example, sine wave power having a frequency of 10 Hz with a phase shifted by 90 °.

When this sine wave power is applied, the magnetic field B ₁ generated by the first and second solenoid coils 14a and 14b
And a magnetic field B ₂ is generated by the third and fourth solenoid coils 15a and 15b, which are combined to generate a combined magnetic field B 2.
To form. This combined magnetic field B has a constant angular velocity 20π (radian / radian / radian / direction) with respect to the electric field E between the electrodes 2 and 3.
It acts on the glow discharge plasma while rotating for sec sec).

As a result, the glow discharge plasma receives a force (EB drift) that rotates at a constant angular velocity. Therefore, the plasma between the electrodes 2 and 3 is swung in all directions in a plane parallel to the substrate 13. The synthetic magnetic field B
The strength may be about 20 to 100 gauss.

The gas supplied from the reaction gas introducing pipe 11 is decomposed by glow discharge plasma generated between the electrodes 2 and 3. The decomposed charged particles such as hydrogen ions have a Coulomb force F ₁ = qE due to the electric field E between the electrodes 2 and 3.
And the Lorentz force F ₂ = q (V · B) by the magnetic field 8 (where V is the velocity of the charged particle), the so-called E ·
Causes a B drift movement.

The charged particles are driven in the direction orthogonal to the electrodes 2 and 3 while being given an initial velocity by the E / B drift. Therefore, charged particles such as hydrogen ions are not
It is rare to hit 3 directly.

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 13, and form an amorphous thin film on the surface thereof. Since the radical Si collides with the charged particles flying in the Lamor orbit, the first to fourth solenoid coils 14a, 1
By rotating the composite magnetic field B generated from 4b, 15a, and 15b in the plane between the electrodes 2 and 3 parallel to the substrate 13, it is possible to uniformly form an amorphous thin film on the surface of the substrate 13.

There is no problem even if the area of the substrate 13 is increased as long as the size of the reaction vessel 1 allows, so that a uniform amorphous thin film can be formed on the surface of the substrate 13 having a large area. Becomes In addition, the plasma confinement effect by the magnetic field can improve the film formation rate.

[0016]

In the conventional device, the magnetic field generated in the direction orthogonal to the discharge electric field between the electrodes for generating glow discharge plasma is increased by rotating in a plane parallel to the substrate. Although it is supposed that it is possible to easily form a film having a uniform area, there are the following problems.

(1) When a large-area film is formed, it is necessary to use a large-area electrode and substrate, but in order to generate stable plasma using the large-area electrode, the frequency of the power source is used. Is easily as low as possible, so a power supply of several tens to several hundreds of Hz is used.

However, under the condition that the frequency becomes low and the ion migration distance during the half cycle exceeds the electrode interval,
As in the case of DC discharge, secondary electrons emitted from the cathode due to ion collision play an essential role in maintaining the plasma. Therefore, if a film is attached to the electrode and insulated, no electric discharge will occur at that part,
In this case, it is necessary to always keep the electrode surface clean.

Therefore, it is necessary to frequently replace and clean the electrodes, which is one of the factors for the high cost of the amorphous silicon solar cell, thin film transistor and the like.

(2) Since the reaction gas is introduced from one direction between the electrodes for generating plasma, the distribution of the reaction gas existing between the electrodes becomes non-uniform. Therefore, even if the magnetic field in the direction orthogonal to the discharge electric field of the electrode for generating glow discharge plasma is rotated in the plane parallel to the substrate, when the large area amorphous silicon thin film is manufactured, the film thickness distribution is ± 20.
% Or less and the film forming rate at 1 Å / sec or more is very difficult. The present invention is intended to solve the above problems.

[0021]

Means for Solving the Problems Plasma CVD of the present invention
The apparatus comprises a reaction vessel, a means for introducing and discharging a reaction gas into the reaction vessel, a ground electrode and a plasma generating electrode housed in the reaction vessel, and glow discharge power to the plasma generating electrode. A power source to be supplied, two pairs of solenoid coils installed across the reaction vessel so as to have axes in directions orthogonal to each other and in directions orthogonal to each other, and power for generating a magnetic field to these solenoid coils. In a plasma enhanced chemical vapor deposition apparatus that forms an amorphous thin film on a substrate that has an alternating current power supply and that is orthogonal to the electric field between the electrodes, the plasma generation electrode penetrates the surface facing the ground electrode. It is characterized in that a plurality of reaction gas introduction holes are formed and the reaction gas is supplied from the back surface thereof.

[0022]

In the above, the reaction gas supplied to the back surface of the plasma generating electrode is supplied to the space between the plasma generating electrode and the ground electrode through the reaction gas introducing hole, is generated between the electrodes, and is generated by the solenoid. It is decomposed by glow discharge plasma rotated by a coil to form an amorphous thin film on the substrate.

In the present invention, a large number of reaction gas introduction holes provided in the plasma generating electrode are used instead of the conventional reaction gas introduction pipe for supplying the reaction gas, so that the reaction gas can be efficiently supplied between the electrodes. It can be introduced, and the distribution of the reaction gas becomes uniform between the electrodes.

Therefore, the plasma density between the electrodes is 2
The averaging is performed more temporally and spatially than the averaging based on only the rotating force (E / B drift) of the synthetic magnetic field generated from the pair of solenoid coils. As a result, the thin film deposited on the substrate surface has a substantially uniform film thickness distribution. Moreover, since a sufficient amount of reaction gas can be efficiently introduced between the electrodes,
The deposition rate can be significantly improved as compared with the conventional apparatus.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma CVD apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, an electrode 101 for generating glow discharge plasma and a ground electrode 3 are arranged parallel to each other in a reaction vessel 1 for reacting a raw material gas. This plasma generating electrode 101 is shown in FIG.
As shown in (b), it has a shower type structure in which the reaction gas introduction holes 102 are uniformly arranged. Since the adjacent reaction gas introduction holes 102 are at regular intervals as shown in FIG. 3, when one reaction gas introduction hole 102 is the center, the other reaction gas introduction holes 102 are arranged at the positions of the vertices of a regular hexagon. ing.

The entire shower-type plasma generating electrode 101 having a large number of reaction gas introduction holes 102 is covered with an earth shield 103 as shown in FIG. 4, and this earth shield 103 is provided in the reaction vessel 1 and the second high frequency wave. It is connected to the ground 9 via the cable 8.

Earth shield 103 and reaction gas introduction hole 1
The gap between the plasma generating electrode 101 and the plasma generating electrode 101 has a value of 0.
The diameter was set to 2 mm, which was shorter than the mean free path of electrons in the pressure range of 05 to 0.5 Torr, the diameter of the reaction gas introduction hole 102 was also set to 2 mm, and the distance between the adjacent reaction gas introduction holes 102 was set to 10 mm.

Further, as shown in FIG. 4, the gap between the earth shield 103 and the plasma generating electrode 101 is sealed in ultrahigh vacuum by using several O-rings 104 made of a non-conductive material. Electric power having a frequency of, for example, 13.56 MHz is supplied to the plasma generating electrode 101 from the high frequency power source 4 via the impedance matching device 5 and the first high frequency cable 6.

The reaction gas is supplied from a cylinder (not shown) having a flow meter through a reaction gas introducing pipe 11, and monosilane, for example, is supplied to the earth shield 103 and the plasma generating electrode 101.
Is introduced into the gap between. The reaction gas between the earth shield 103 and the plasma generation electrode 101 is supplied between the ground electrode 3 and the plasma generation electrode 101 through the shower-shaped reaction gas introduction hole 102 of the plasma generation electrode 101, and the reaction container The reaction gas in 1 is exhausted through an exhaust pipe 12 by a vacuum pump (not shown).

The substrate 13 is supported and installed on the ground electrode 3 via a substrate holder (not shown) in parallel with the plasma generating electrode 101 having the reaction gas introduction hole 102 as shown in FIG.

Around the reaction vessel 1, solenoid coils 14a, 14b, 15 of finite length having first to fourth thicknesses are provided.
a and 15b are installed, as shown in FIG.
And the second solenoid coils 14a and 14b form a pair, and the third and fourth solenoid coils 15a and 15b form a pair so that their respective axial cores are orthogonal to each other, that is, in the x-axis direction and the y-axis direction. It is arranged to match.

The first and second solenoid coils 14a,
14b is supplied with electric power having a sine waveform from one output terminal of the phase variable two-output oscillator 16 via the first power amplifier 17. Further, the third and fourth solenoid coils 15a and 15b are supplied with sinusoidal power from the other output terminal of the phase variable two-output oscillator 16 via the second power amplifier 18.

The phase variable two-output oscillator 16 can output two sine wave signals, and two sine wave signals whose relative phases can be arbitrarily set. The magnetic fields generated by the first and second solenoid coils 14a, 14b have a substantially uniform strength distribution in the axial direction (x-axis direction) as shown in FIG. The magnetic fields generated by the third and fourth solenoid coils 15a and 15b also have a substantially uniform strength distribution in the axial direction (y-axis direction) as in FIG.

Next, the production of, for example, an amorphous silicon thin film using the above apparatus will be described below.
First, the vacuum pump is driven to sufficiently exhaust the inside of the reaction vessel 1 (for example, 1 × 10 ⁻⁷ Torr), and then the reaction gas introduction pipe 1
1, for example, monosilane is supplied at a flow rate of 50 to 100 cc / min, and the pressure in the reaction vessel 1 is set to 0.05 to 0.5 To.
keep to rr.

Next, power is supplied from the high frequency power source 4 to the plasma generating electrode 101 via the impedance matching device 5 and the power introduction terminal 7 and the like to generate glow discharge plasma of monosilane between the electrodes. The high frequency power source 4 is preferably 13.56 MHz.

On the other hand, the first and second solenoid coils 1
4a, 14b and third and fourth solenoid coils 1
5a and 15b are fed from the phase-variable 2-output oscillator 16 via the first and second power amplifiers 17 and 18, respectively.
Apply output. This output is, for example, sine wave power having a frequency of 10 Hz and a phase shifted by 90 °.

When this sinusoidal power is applied, a combined magnetic field of the magnetic fields of the first and second solenoid coils 14a and 14b and the magnetic fields of the third and fourth solenoid coils 15a and 15b is generated. This composite magnetic field acts on the glow discharge plasma while rotating at a constant angular velocity of 20π (radian / sec) in the direction orthogonal to the electric field between the plasma generating electrode 101 and the ground electrode 3.

As a result, the glow discharge plasma receives a force (EB drift) that rotates at a constant angular velocity. Therefore, the plasma between the plasma generating electrode 101 and the ground electrode 3 is swung in all directions in a plane parallel to the substrate 13. The strength of the synthetic magnetic field may be about 20 to 100 Gauss.

The thickness distribution and deposition rate of the amorphous silicon thin film are determined by the electrode area, electrode spacing, reaction gas flow rate, pressure, power supplied between the electrodes, and synthetic magnetic field applied to the glow discharge plasma. Depends on strength etc.

In this embodiment, an amorphous silicon thin film is manufactured by using the apparatus of this embodiment and the conventional apparatus for confirming the performance, and the contents will be described below. In this manufacturing, a circular electrode having a diameter of 800 mm was used as the electrode, and the substrate 13 was 500 mm × 500 mm #.
7059 non-alkali glass was used.

As the reaction gas, 100% monosilane gas was used, supplied at a flow rate of 50 cc / min, and the pressure in the reaction vessel 1 was set to 0.1 Torr. Plasma generating electrode 10
A high-frequency power of 50 W is applied to 1 and the strength of the synthetic magnetic field applied by the solenoid coils 14a, 14b, 15a, 15b is 0, 20, 40, 60, 80, 100.
Set to Gauss.

FIG. 7 shows the film thickness distributions of the amorphous silicon thin films manufactured by using the apparatus of this embodiment and the conventional apparatus. The strength of the synthetic magnetic field at this time is 10
It was set to 0 gauss. It can be seen from FIG. 7 that in the case of this embodiment, a film having a uniform film thickness can be obtained over a wide area as compared with the case of the conventional device.

FIG. 8 shows the relationship between the magnetic field strength obtained in the above manufacturing process and the film formation rate of the amorphous silicon thin film. It can be seen from FIG. 8 that the film forming rate can be remarkably improved in the case of the apparatus of this embodiment as compared with the conventional apparatus. Further, when the magnetic field strength is increased, the effect of improving the film formation rate is great.

In this embodiment, the shower-type plasma generating electrode has a circular shape, but it may have a circular shape or a rectangular shape. Further, the diameter of the reaction gas introduction hole of the plasma generating electrode is preferably 3 mm or less.

When the diameter of the reaction gas introducing hole exceeds 3 mm, it becomes longer than the mean free path of electrons at a pressure of 0.05 to 0.5 Torr, so that plasma is generated in the reaction gas introducing hole, When the plasma density between the electrodes decreases and becomes non-uniform, the deposition rate of the amorphous thin film deposited on the substrate decreases,
This is because it causes non-uniformity of the film thickness distribution of the amorphous thin film of about 30%.

[0047]

According to the plasma CVD apparatus of the present invention, a plurality of reaction gas introduction holes are provided in the plasma generation electrode which is arranged in the reaction vessel and faces the ground electrode, and the reaction gas is supplied to the back surface of the plasma generation electrode. After that, by supplying the reactive gas between the electrodes through the reactive gas introduction hole, the reactive gas can be efficiently introduced between the electrodes and the distribution thereof can be made uniform. It is possible to form an amorphous thin film having a large area at high speed, and to realize a device having an extremely large industrial value in the manufacturing field such as amorphous silicon solar cells, thin film transistors for liquid crystal displays, and optoelectronic devices.

[Brief description of drawings]

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

2A and 2B are explanatory views of a plasma generating electrode having a reaction gas introducing hole according to the above embodiment, FIG. 2A is a plan view, and FIG.
Is a sectional view.

FIG. 3 is a plan view showing a positional relationship of reaction gas introduction holes of the plasma generating electrode according to the above-mentioned embodiment.

FIG. 4 is a detailed view of a plasma generating electrode having a reaction gas introducing hole according to the above embodiment.

FIG. 5 is a plan view showing a positional relationship between a reaction container and two pairs of solenoid coils according to the above embodiment.

FIG. 6 is an explanatory diagram of a magnetic field strength distribution between solenoid coils according to the above-described embodiment.

FIG. 7 is a characteristic diagram showing a film thickness distribution of an amorphous silicon thin film manufactured by the apparatus of the one embodiment and a conventional apparatus.

FIG. 8 is a characteristic diagram showing the relationship between the film formation rate and the magnetic field strength of the amorphous silicon thin film manufactured by the apparatus of the one embodiment and the conventional apparatus.

FIG. 9 is an explanatory diagram of a conventional plasma CVD apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction container 3 Ground electrode 4 High frequency power supply 5 Impedance matching device 9 Earth 11 Reaction gas introduction pipe 12 Exhaust pipe 13 Substrate 14a, 14b, 15a, 15b Solenoid coil 16 Phase variable 2 output oscillator 17, 18 Amplifier 101 Plasma generation electrode 102 Reaction gas introduction hole 103 Earth shield

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

Claims (1)

[Claims] 1. A reaction vessel, means for introducing and discharging a reaction gas into the reaction vessel, a ground electrode and a plasma generating electrode housed in the reaction vessel, and a glow discharge for the plasma generating electrode. A power supply for supplying electric power, two pairs of solenoid coils installed across the reaction vessel so as to have axes in directions orthogonal to each other and in directions orthogonal to each other, and electric power for generating magnetic fields in these solenoid coils. A plasma chemical vapor deposition apparatus for forming an amorphous thin film on a substrate supported by an alternating current power supply for supplying the electric field between the electrodes, the plasma generation electrode being opposite to a ground electrode. A plurality of reaction gas introduction holes penetrating the substrate are formed, and a reaction gas is supplied from the rear surface of the plasma chemical vapor deposition device.