JPS6410595B2 - - Google Patents

Description

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

When trying to use plasma phenomena to decompose a raw material gas for film formation and form a film with desired properties on a predetermined support, especially in the case of a large-area film, However, it is much more difficult to uniformize the film thickness and physical properties such as electrical, optical, or photoelectric properties compared to the usual vacuum evaporation method.

For example, a gas such as SiH ₄ , Si ₂ H ₆ , SiF _4, etc. is decomposed using discharge energy and a film of amorphous silicon hydride (hereinafter referred to as a-Si:H) or amorphous silicon containing halogen atoms (hereinafter referred to as a-Si:H) is formed on the support. When attempting to form a film (hereinafter referred to as a-Si:X) and utilize the electrical properties of this film, the electrical properties of this film largely depend on the discharge intensity during film formation.
In order to obtain uniform electrical properties over the entire area of the film, it is necessary to make the discharge intensity uniform over the entire area where the film is formed.

However, in the conventional method, it has been extremely difficult to make the discharge intensity uniform, especially when forming a film with a large area.

Furthermore, in glow discharge deposition methods that utilize plasma phenomena, the film formation rate is generally slower than that in normal vacuum evaporation methods.

For this reason, it has been proposed to increase the power of the glow discharge, but it is known that for a-Si:H or a-Si:X, if the discharge power is increased too much, the electrical properties of the film will deteriorate. It is being

In addition, the positional relationship between the electrode and the support that forms the film, as well as the structure and arrangement of the electrode, greatly affect the uniformity of film thickness and properties, but conventional methods are not always satisfactory in this respect as well. Therefore, it is unsuitable especially in the reproducibility of film formation over a large area and in the mass production of films with constant characteristics.

In other books, when a film is formed on a large-area cylindrical support by a glow discharge method that utilizes a plasma phenomenon, an electrode is placed outside the cylindrical support and a high-frequency electric field is generated between the cylindrical support and the cylindrical support. The most common types are the so-called capacitance type, in which a glow discharge is generated by applying an electric current, and the inductance type, in which a coil is placed around a cylindrical support and a high-frequency current is passed through the coil to generate a glow discharge. It is.

Among these, the inductance type does not apply an electric field directly to the support and the film formed on the support, so the support and the film formed are less likely to be damaged by glow discharge. It has the advantage that there is no need to pay attention to the electrical connection between the high-frequency power generator and the high-frequency power generator, but it is more difficult than conventional capacitance types to generate a uniform glow discharge over a large area. Ta.

In order to improve this point and form a uniform film on a large-area support, conventional attempts have been made to form a film while reciprocating a cylindrical support in the longitudinal direction.

However, this method requires a device to drive the support, and in particular, in order to perform reciprocating motion, it is necessary to enlarge the deposition chamber in which the glow discharge is performed.
Not only does this increase the size of the equipment, but it also takes a great deal of time to reduce the pressure inside the deposition chamber, reducing productivity.
Another disadvantage is that it is difficult to increase the film formation rate because glow discharge of sufficient intensity is generated only in a small portion of the deposition chamber.

As described above, the conventional method has the above-mentioned drawbacks, and there is still a need for improvement in terms of reproducibility, mass production, etc., especially when it comes to forming a large-area film with uniform properties and film thickness. is pointed out.

The present invention has been made in view of the above points, and even if the film has a large area, the entire area can be
An object of the present invention is to provide a method for forming a film using glow discharge, which can form a film with substantially uniform physical properties and thickness with good reproducibility.

Another object of the present invention is to provide a film forming method that is extremely effective for mass production.

In the film forming method of the present invention, a support for film formation is installed in a deposition chamber that can be made under reduced pressure, and when forming a film by causing glow discharge in a source gas introduced into the deposition chamber, the support for film formation is It is characterized by forming a film by arranging a member made of an insulating material and having high magnetic permeability at the end of the material.

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

FIG. 1 is a schematic explanatory diagram showing one preferred example of an apparatus capable of embodying the film forming method using glow discharge of the present invention. The deposition chamber 1, which can be made to have a reduced pressure, has a bell jar 3 made of, for example, quartz glass, which is also commonly used, installed on a base plate 2 having a structure similar to that used in a normal glow discharge deposition apparatus, via an O-ring. Inside the deposition chamber 1, a fixing member 5 for setting a support 4 for film formation at a predetermined position is fixed at a predetermined position in the lower part of the deposition chamber 1, as shown in the figure. In the apparatus shown in FIG. 1, the fixing member 5 is connected at the bottom to a pipe 6 through which raw material gas for film formation is introduced into the deposition chamber 1 from below, and is introduced into the fixing member 5 through the pipe 6. The raw material gas is introduced into the deposition chamber 1 through a plurality of gas outlets 7 provided at the upper end of the fixing member 5.

A coil 8 is wound around the outside of the bell gear 3 and is connected through a coaxial cable 9 to a high frequency power source (not shown) for causing glow discharge.

One end of the coil 8 is connected to a coaxial cable 9, and the other end is grounded via a shield 13.

The coil 8 is provided outside the deposition chamber 1 and is generally arranged in this manner, but it can also be provided inside the deposition chamber 1.

Numeral 10 is a heater for heating the support 4 to a desired temperature as necessary when forming a film on the support 4, and is inserted and fixed inside the support 4. The heating temperature of the support 4 is detected by a thermocouple 11 provided in contact with the inside of the support 4,
The power supplied to the heater 10 is automatically controlled so that the support 4 is maintained at a desired temperature during film formation.

The degree of vacuum within the deposition chamber 1 is measured by a vacuum gauge 12.

The support 4 is rotated about the fixed member 5 at a predetermined rotational speed during film formation in order to avoid position dependence of discharge intensity as much as possible.

In this way, by rotating the support 4 around the fixing member 5 during film formation, it is possible to average out the positional dependence of the discharge intensity, resulting in more uniform characteristics and a more uniform film thickness. can be formed on the support 4.

In order to form a predetermined film on a support using the apparatus shown in FIG. 4 is fixedly installed on a fixing member 5, the bell gear 3 is set on the base plate 2, and the deposition chamber 1 is evacuated from the lower part thereof so that the inside of the deposition chamber 1 has a predetermined degree of vacuum.

When the inside of the deposition chamber 1 reaches a predetermined degree of vacuum, a raw material gas for film formation, for example, if an a-Si:H film is to be formed, a silane gas such as SiH ₄ is introduced into the pipe 6.
It is introduced into the deposition chamber 1 from the outside through the tank so that a predetermined internal pressure is reached. When the inside of the deposition chamber 1 is filled with the raw material gas for film formation at a predetermined internal pressure, high-frequency power is supplied to the coil 8 to generate a glow discharge inside the deposition chamber 1, turning the gas inside the deposition chamber 1 into plasma. to form a film on the support 4. The frequency of high-frequency power is usually 13.56MHz, but other frequencies are also possible.

By rotating the support 4 during film formation, it is possible to average out the discharge intensity unevenness caused by non-uniform distribution of gas flow rate, and to achieve uniform physical properties and uniform film thickness over a large area. It is possible to obtain a film having the following properties. Further, regarding the gas fluid velocity, the gas decomposition rate is taken into consideration, and if the decomposition rate is high, it is preferable to increase the gas fluid velocity.

Furthermore, the inlet for the raw material gas into the deposition chamber 1 does not necessarily need to be provided at the top of the fixing member 5 as shown in FIG. It may be provided at any position within the deposition chamber 1 as long as it is devised. However, it is better to provide an opening for introducing the raw material gas at a position far from the exhaust port of the deposition chamber 1, since the introduced raw material gas can be turned into plasma more efficiently. It is more convenient to provide an inlet because the gas flow rate can be made more uniform. Reference numeral 13 denotes a shield for shielding a high frequency electric field, and is formed of, for example, a metal mesh.

14 and 14' are members arranged according to the present invention, and are made of ferrite which is insulating and has high magnetic permeability.

By arranging a member having high magnetic permeability in this way, the glow discharge intensity is made uniform over the entire surface of the support, and a film of uniform quality is sufficiently formed on the support.

FIG. 2 shows members 14 and 14 in the apparatus of FIG.
By arranging 14' above and below the support 4, the state of the high frequency magnetic field generated by passing a high frequency current through the coil 8 is shown. By arranging the two members 14 and 14' above and below the support 4 as shown by the dotted line, the high-frequency magnetic field can make the magnetic flux density approximately uniform between the members 14 and 14', and therefore the support A plasma of uniform intensity is formed in the entire area.

The material constituting the member having high magnetic permeability used in the present invention needs to be an insulator since it is used at high frequencies. This is because eddy currents occur in conductors such as iron, which not only do not exhibit high magnetic permeability to high frequencies, but also absorb high frequency energy and generate heat.

As the insulating material having high magnetic permeability used in the method of the present invention, ferrite is preferable, and among them, it is necessary to use a material especially designed for high frequencies.

In FIGS. 1 and 2, the members 14 and 14' made of a high magnetic permeability material are placed apart from the support 4, but they may be placed in contact with the support 4.

Alternatively, it may be provided outside the deposition chamber 1 at a further distance. In this case, although there is no effect unless a material with a sufficiently large magnetic permeability is used, there is an advantage that the volume of the deposition chamber 1 can be designed to be small.

In order to further increase the effect, it is also effective to provide a member made of a material with high magnetic permeability on the outside of the coil 8 so that the device is covered with a member made of a material with high magnetic permeability. It is.

Example Next, the apparatus shown in FIG. 1 and the members 14, 14' shown in the figure
An example will be shown in which a photoconductive member was manufactured using the following procedure using a 99.9% Fe ₃ O ₄ ferrite material processed into a disk shape with a diameter of 300 mm and a thickness of 70 mm.

As a cylindrical support, a JIS5000 mirror-finished aluminum cylinder with a diameter of 200 mm, a length of 300 mm, and a thickness of 5 mm was used, and after cleaning with trichloroethane, this was installed in the bell gear 3 as shown in Figure 1. .

Next, the inside of the bell jar 3 was evacuated to a pressure of 10 ^-3 torr using a vacuum pump (not shown). In this state, the support was rotated by a drive system (not shown) at a rate of one revolution every 5 minutes, and the support was heated by the heater 10 so that the temperature indicated by the thermoelectric body 11 was 300°C. After the temperature of the support stabilized at 300°C, SiH ₄ was introduced through the gas introduction pipe 6 and from the gas release hole 7.
Gas was discharged into Belgear 3 at a flow rate of 200 sccm. Next, while watching the vacuum gauge 12, operate the exhaust valve (not shown) to increase the pressure inside the bell gear 3.
Adjusted to 0.5torr. The pressure inside bell jar 3 is
After stabilizing at 0.5torr, turn on the RF power (not shown),
Frequency through coaxial cable 9 and coil 8
13.56MHz, 200W RF power was input into Bergier 3 to generate a glow discharge. this state
After maintaining the temperature for 100 minutes, the RF power was turned off, the introduction of gas and the power supply to the heater were stopped, and the inside of the bell gear 3 was again brought to a vacuum of 10 ^-3 torr. This state was maintained for about 1 hour until the support temperature indicated by the thermocouple 11 reached
When the temperature dropped below 100°C, a leak valve (not shown) was opened to bring the inside of the bell jar 3 to atmospheric pressure, and the support on which the deposited film was formed was taken out.

The support on which the deposited film has been formed (hereinafter abbreviated as "photoconductive member") is attached to each part of 20 mm, 150 mm, and 280 mm from the upper end of the cylindrical photoconductive member (hereinafter referred to as "photoconductive member").
Four points are placed at equal intervals in the circumferential direction on the circumference (each abbreviated as "upper", "middle", and "lower"), and each point of the upper, middle, and lower part is placed in the longitudinal direction of the support. Twelve measurement points arranged in a straight line were first subjected to film thickness measurement using an eddy current film thickness meter.

When the film thickness of each part was measured, it was confirmed that it was uniform as shown in Table 1.

Next, using the same sample, a translucent chrome electrode with a light transmittance of 0.5 was formed by vapor deposition at the position corresponding to the point where the film thickness was measured as described above, and this was used as one electrode.
In addition, the electrical characteristics of each part were measured using the support as the other electrode. As for the electrical properties, evaluation items were dark conductivity (σb) and photoconductivity (σp) when irradiated with a He--Ne laser with a power of 5 mW. The results showed that the upper, middle, and lower measurement points had the electrical characteristics shown in Table 1, and it was confirmed that they had good characteristics as a photoconductive member and were also excellent in uniformity.

Comparative Example 1 Next, as a first comparative example, a photoconductive member was formed using the same apparatus configuration and film forming conditions as in the previous example, except that members 14 and 14' were removed, and was subjected to the same evaluation. As a result, the film thickness distribution in the circumferential direction was within the range of about ±10% as shown in Table 2, but in the long axis direction of the cylinder, that is, the upper, middle, and lower parts.
A large variation was observed.

As for the electrical characteristics, as can be seen from Table 2, the middle part showed the same characteristics as the case of the above example, but the upper and lower parts showed σp compared to the middle part.
It was found that the values of σp and σp tended to be inferior by more than one order of magnitude in the lower part, and there was no large difference in the values of σp and σp, indicating that the characteristics were not suitable for a photoconductive member. In addition, in terms of uniformity, there were large variations in the long axis direction, and it was considered that it could not be said to be practically good.

Comparative Example 2 Next, as another comparative example, members 14 and 1
4', the shape was the same as in the above example, but the material was changed to SUS304, which is conductive and has high magnetic permeability, and other conditions were the same as in the above example and comparative example 1. A photoconductive member was formed and subjected to the same evaluation.

As a result, the values shown in Table 3 were obtained for film thickness and electrical properties.

As can be seen from these results, it was confirmed that, like Comparative Example 1, the variation in the long axis direction tended to be large, and the results were even worse than Comparative Example 1 in terms of absolute values.

For these reasons, especially when forming a film by electrical discharge on a long support, it is recommended to install a member made of a material with high magnetic permeability at the end of the support in order to equalize the discharge state and, in turn, to achieve high uniformity. It was found to be effective in obtaining deposited films.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of an apparatus that embodies the film forming method of the present invention, and FIG. 2 is a schematic explanatory diagram for explaining the state of the high-frequency magnetic field formed in the apparatus of FIG. 1. It is a diagram.

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Claims (1)

[Scope of Claims] 1. When a film-forming support is installed in a deposition chamber that can be reduced in pressure, and a film is formed by generating a glow discharge in a source gas introduced into the deposition chamber, the film-forming support is A film forming method characterized by forming a film by arranging a member made of a material that is insulating and has high magnetic permeability at the end of the film. 2. The film forming method according to claim 1, wherein the insulating material having high magnetic permeability is ferrite.