JPS6315348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film forming method that is effective for forming, for example, a photoconductive film, a semiconductor film, an inorganic insulating film, or an organic resin using glow discharge.

When attempting to form a film with desired characteristics on a predetermined support by introducing a film-forming gas into a deposition chamber that can be under reduced pressure and utilizing the plasma phenomenon caused by glow discharge, it is especially important to form a film with desired characteristics on a given support. In some cases, increasing the film formation rate while ensuring uniformity of the film thickness, physical properties such as electrical, optical, or photoelectric properties, and uniformity of quality over the entire area, This method is much more difficult than the usual vacuum evaporation method.

For example, when SiH ₄ gas is decomposed using discharge energy to form an amorphous silicon hydride (hereinafter referred to as a-Si:H) film on a support, and the electrical properties of this film are to be utilized. Since the electrical properties of this film greatly depend on the discharge intensity during film formation, in order to obtain uniform electrical properties over the entire film area, it is necessary to equalize the discharge intensity over the entire film formation area. Unless the discharge intensity is made uniform and the film formation rate is improved, reproducibility, productivity, and mass production will not be fully satisfied, and industrialization will not be possible.

By the way, the uniformity of this discharge intensity is determined by the electric field strength,
It mainly depends on factors such as gas flow rate, gas pressure, arrangement of gas introduction and discharge positions, and the shape and arrangement of discharge electrodes, and conventionally proposed film formation methods do not uniquely address the above factors. It is not possible to obtain a uniform discharge intensity that optimizes the film formation conditions.
At present, film formation is performed under a certain degree of relaxed conditions.

In particular, the electric field strength has a great influence on the uniformity of the properties of the deposited film that is formed, but this electric field strength largely depends on other factors in the film formation conditions. The non-uniformity of the electric field intensity, the change in the intensity over time, and the magnitude of the intensity are factors that greatly influence the characteristics of the formed film. For example, a direct current electric field or a high frequency electric field has been used as the electric field for conventional discharge, and attempts have been made to increase the electric field strength to increase the film formation rate, but in the case of the direct current electric field method, Although the effective electric field based on the high frequency electric field method is strong,
It strongly depends on the gas pressure during film formation, and as the pressure becomes lower, the discharge decreases and eventually stops.
Conversely, as the gas pressure becomes high, the electric field strength rapidly weakens as you move closer to the center of the spatial region where the discharge is formed, causing the same phenomenon as in the case of low pressure, which is inconvenient. be.

As described above, in the DC electric field method, the allowable range of gas pressure that allows glow discharge is extremely narrow, and it is greatly affected by fluctuations in gas pressure, making it unsuitable for producing films with uniform characteristics at high speed. There are many aspects to it.

On the other hand, in the case of the high-frequency electric field method, the discharge is more stable against fluctuations in gas pressure than in the DC electric field method, and in this respect it has an advantage; It has the disadvantage that the film formation rate cannot be increased that much. For example, according to experiments conducted by the present inventors,
It is about 7 Å/sec at most. Therefore, for example, a-
When creating a film with an extremely low growth rate, such as a Si:H film, it takes a long time to create the film, which reduces productivity.
It is not suitable for mass production.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a film forming method capable of manufacturing a film with uniform characteristics over a large area with high efficiency.

In the film forming method of the present invention, a gas for forming a deposited film is introduced into a deposition chamber that can be reduced in pressure, a glow discharge is generated, and a plasma atmosphere of the gas is formed. A film forming method for forming a deposited film on a support for formation is characterized in that the plasma atmosphere is formed in the coexistence of a direct current electric field and an alternating electric field.
The film forming method of the present invention, which has these characteristics, has significantly higher efficiency and speed than conventional methods, has excellent physical properties, optical properties, and photoelectric properties, and can cover all areas of the formed film. In this case, those having uniform characteristics and film thickness and having a large area can be easily formed. In particular, the film forming method of the present invention can easily form an a-Si:H film with excellent electrical and photoelectric properties at high speed with good reproducibility, and for example, compared to the conventional glow discharge method, at least A film with excellent photoelectric and electrical properties can be obtained at a film formation rate 5 to 10 times faster.

In the present invention, an alternating electric field is preferably employed as the alternating electric field, and either an inductive method or a capacitive method may be employed to form the electric field.

The electrical energy required to form such an alternating electric field is usually 50W to 2KW, preferably 100W to 1KW, in the case of the inductive method.
In the case of capacitive method, usually 5W~
It is desirable that the power is 500W, preferably 10W to 100W.

Although the purpose of the present invention can be achieved more effectively with a higher frequency, from the point of view of practicality, the commonly used RF (radio frequency)
Frequencies in the region are preferably adopted, for example 13.56Mz
is convenient.

As for the electrical energy required to form a DC electric field, the absolute value of the potential difference between the electrodes required to form a DC electric field is usually 0.1V to 1KV, preferably 1V to
It is desirable to set it to 500V.

In the present invention, the support for forming a deposited film is
Although it may be installed in a spatial region where a plasma atmosphere is formed or in any spatial region, the film can be formed with higher efficiency and characteristics depending on the type of deposited film to be formed. The resulting placement of the membrane is determined to be uniform and excellent.

Normally, the support is installed on either side of the electrodes that form the DC electric field, and is preferably selected at a position in contact with one of the electrodes or in the vicinity thereof.

For example, if an a-Si:H film is to be formed, it is more preferable from a comprehensive viewpoint to install it on the cathode side of the electrode for forming a DC electric field.

The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic explanatory diagram showing one preferred example of a deposition apparatus that embodies the film forming method of the present invention. The deposition apparatus 100 shown in FIG. 1 includes electrodes 107-1 and 107-2 for forming an electric field to form plasma inside a deposition chamber 101, an RF coil 110, and a deposited film on the electrode 107-1 side. A forming support 109 is provided in each case.

The deposition chamber 101 is connected to an exhaust pipe 112 for exhausting the inside of the chamber 101, and a gas introduction pipe 106 for introducing gas for forming a deposited film. Voltage is applied to the electrodes 107-1, 107-2 from an external DC power source 108 through lead wires 113-1, 113-2, and voltage is applied to the RF coil 110 from an external RF power source 111 through a lead wire 114. A predetermined power is applied. To form a film using the apparatus 100 shown in FIG.
The gas flow rate control valve 104 is closed, the main valve 103 is fully opened, and the inside of the deposition chamber 101 is evacuated by the exhaust device 102 to achieve a predetermined degree of vacuum. When the desired degree of vacuum is achieved in the deposition chamber 101, the support 109 is heated to a predetermined temperature using an appropriate means such as a heater or an infrared lamp, if necessary. When the interior of the deposition chamber 101 is ready for film formation, three valves 115-1,
115-2, 115-3, and gradually open the gas flow rate adjustment valve 104.
A desired gas is introduced into the deposition chamber 101 from a desired gas cylinder 105 .

When the desired degree of vacuum is reached in the deposition chamber 101 by introducing the gas, the electrodes 107-1, 107
- electrode 1 so that a predetermined potential difference is formed between the electrodes 1 and 2.
07 from the DC power supply 102, and alternating power is applied to the RF coil 110 from the RF power supply 111 to generate glow discharge in the electrodes 107-1 and 107-2. to form a plasma atmosphere. Preferably, the plasma atmosphere is maintained continuously until the end of film formation, in order to form a film with uniform characteristics.

The distance between the electrodes 107-1 and 107-2 can be arbitrarily set depending on the type and size of the film to be formed, the size of the deposition apparatus 100, etc. If it is to be formed on a 70 cm square plane area, it should be set between 3 and 5 cm.

Next, an example will be shown in which an a-Si:H film was formed using an apparatus similar to that shown in FIG.

After preparing for film formation in the deposition chamber 101 as described above, the valves 115-1 and 115-2 are opened so that the mixing ratio becomes 9:1, and the gas flow rate control valve 104 is gradually opened. With a flow rate of 50SCCM
A mixed gas of H ₂ and SiH ₄ was introduced into the deposition chamber 101 .
At this time, the opening/closing amount of the main valve 103 was adjusted so that the degree of vacuum in the deposition chamber 101 was in the range of 1 to 10 Torr.

At this time, the dimensions of each part of the apparatus and the dimensions and material of the material to be treated were as follows.

Dimensions of electrode 120×120mm Distance between electrodes 50mm Dimensions of material to be treated 100×100mm Material of material to be treated Corning 7059 glass In this state, turn on power supply 108 and turn electrode 1
A potential difference of 50V was created between 07-1 and 107-2. Further, the RF power supply 111 was turned on and 10W of power at 13.56Mz was continuously applied to the RF coil 110. In this case, a glow discharge was generated between the electrodes 107-1 and 107-2, a plasma atmosphere was formed, and an a-Si:H film was formed on the support 109.

At this time, the film is formed at a deposition rate of approximately 30 Å/sec up to a film thickness of 10 μm, and even when the film thickness reaches 50 μm, the deposition rate is approximately 20 Å/sec, making it extremely efficient and highly efficient. It was found that an a-Si:H film was formed at a high speed.

Further, the obtained a-Si:H film had an extremely uniform film thickness with a film thickness distribution within 5% over the entire area.

Furthermore, the dark resistance value was around 10 ^-12 Ωcm, and the resistance value changed by several orders of magnitude with room light, indicating that it had excellent properties as a uniform and good photoconductor.

FIG. 2 is a schematic partially cutaway perspective view showing the arrangement of electrodes for forming a film on a cylindrical support for film formation, such as a substrate for an electrophotographic photoreceptor. A cylindrical support body 201 for film formation is placed inside the RF coil 202 and also serves as one electrode for forming a DC electric field. The other electrode 203 for forming a DC electric field, which faces the electrode-cum-support body 201, is arranged outside the RF coil 202 as shown in the figure.

In the case of the apparatus shown in FIG. 2, the gas for forming the deposited film is introduced into the deposition chamber through the RF coil 202.
It is made up of a large number of gas discharge ports 204, which are fine holes provided in the RF coil 202.

The RF coil 202 is imaged by an RF power source (not shown), and the electrode 203 and the support 201 are each electrically connected to a power source (not shown) for forming a DC electric field. In the case of the example shown in FIG. 2, since the support for film formation also serves as one electrode for forming a DC electric field, it is possible to prevent contamination of the electrode and save space for installing parts, and the RF coil 202 Since the film-forming gas is introduced into the deposition chamber through the film, the gas distribution can be made even more uniform, making it extremely economical and suitable for mass production.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one preferred example of a deposition apparatus embodying the film forming method of the present invention, and FIG.
The figure is a schematic partially cutaway perspective view showing one of the other examples. 100... Deposition device, 101... Deposition chamber, 102...
Exhaust device, 103... Main valve, 104... Gas flow rate adjustment valve, 105... Gas cylinder, 106...
Gas introduction pipe, 107... Electrode, 108... DC power supply, 109... Support body, 110... RF coil, 11
1...RF power supply, 112...exhaust pipe, 113,1
14... Lead wire, 115... Valve, 201... Cylindrical support, 202... RF coil, 203... Electrode,
204...Gas discharge port.

Claims (1)

[Claims] 1. A gas for forming a deposited film is introduced into a deposition chamber that can be reduced in pressure, and a glow discharge is generated to form a plasma atmosphere of the gas, and the gas is deposited on a support for forming a film that has been installed in advance in the deposition chamber. A film forming method for forming a deposited film, characterized in that the plasma atmosphere is formed under the coexistence of a direct current electric field and an alternating electric field.