JPH07245269A - Plasma treatment device and method - Google Patents

Abstract

PURPOSE:To provide a plasma treatment device and method which can uniformly perform plasma treatment of a relatively large-area substrate at a high treatment rate which was not attained by a conventional plasma process. CONSTITUTION:In a plasma treatment device where a cathode electrode 2 and an opposing electrode opposing the cathode electrode are provided in a reaction container whose pressure can be reduced, plasma is generated between the cathode electrode and the opposing electrode by applying a high-frequency power whose frequency is equal to and more than 30MHz and is equal to and less than 300MHz to the cathode electrode with capacitance coupling via a matching circuit 8, and plasma treatment is performed onto a substrate to be treated which is laid out on the opposing electrode, soft magnetic material 12 is laid out at one part of a high-frequency transmission path between the cathode electrode and/or the matching circuit and the cathode electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a processing method, and more particularly to a crystalline material useful as a photoconductor device for electrophotography as a semiconductor device, a line sensor for image input, an imaging device, a photovoltaic device and the like. Alternatively, a plasma CV capable of suitably forming a non-single crystalline functional deposited film
D apparatus and film forming method, sputtering apparatus and film forming method capable of suitably forming an insulating film, a metal wiring, etc. as a semiconductor device or an optical element, or plasma processing apparatus and processing such as an etching apparatus and method for a semiconductor device Regarding the method.

[0002]

2. Description of the Related Art There are various methods for plasma processing used in the manufacture of semiconductors and the like according to their respective applications.
For example, various kinds of plasma such as an oxide film, a nitride film and an amorphous silicon-based semiconductor film formed by plasma CVD method, a metal wiring film formed by sputtering method, or a fine processing technique by etching are used. Devices and methods that utilize the characteristics are used. Further, in recent years, there has been a strong demand for improvement in film quality and processing capacity, and various devices have been studied. In particular, plasma processes using high-frequency power are widely used because of advantages such as stability of discharge and application to insulating materials such as oxide films and nitride films.

Conventionally, the oscillating frequency of a high frequency power source for discharge used in plasma processes such as plasma CVD is 13.
56 MHz is common. FIG. 5 shows an example of a plasma CVD apparatus generally used for forming a deposited film. FIG. 5 shows a film forming apparatus for forming an amorphous silicon film (hereinafter referred to as an a-Si film) for a cylindrical electrophotographic photosensitive member, and a film forming method for an a-Si film will be described using the film forming apparatus.

Insulating material 11 is placed in reaction vessel 1 capable of depressurizing.
A cylindrical cathode electrode 2 electrically insulated from the reaction vessel 1 by the above, and a cylindrical film-forming substrate 3 as a counter electrode.
Are arranged. The film formation substrate 3 is held by a substrate holder 4 having a rotation mechanism driven by a motor M,
It is heated to a predetermined temperature from the inside by the heater 5 inside. The high frequency power supply 7 is connected to the cathode electrode 2 via a matching circuit 8. Reference numeral 9 is a vacuum exhaust means, and 10 is a gas supply means.

After the inside of the reaction vessel 1 has been evacuated to a high vacuum by the vacuum evacuation means 9, SiH is supplied by the gas supply means 10.
Source gas such as ₄ , Si ₂ H ₆ , CH ₄ , C ₂ H ₆ and B ₂ H ₆
A doping gas such as is introduced and the pressure is maintained at several tens of mTorr to several Torr. From high frequency power supply 7.
By supplying high-frequency power of 56 MHz to the cathode electrode 2,
An a-Si film is formed on the film-forming substrate 3 heated by the heater 5 to about 200 ° C. to 350 ° C. by generating plasma between the cathode electrode 2 and the film-forming substrate 3 to decompose the raw material gas. Deposit.

The deposition rate for obtaining an a-Si film satisfying the performance of the electrophotographic photoreceptor by the above film forming method is about 6 (μm / hour) at the maximum. It becomes impossible to obtain the physical characteristics of the body. When an a-Si film is used as the electrophotographic photoreceptor,
Since a film thickness of at least about 20 to 30 μm is required to obtain the charging ability, it takes a long time to manufacture the electrophotographic photoreceptor.

By the way, in recent years, parallel plate type plasma C
Report on plasma CVD method using VD equipment and high frequency power supply of 13.56MHz or more (Plasma Chemist
ry and Plasma Processing, Vol7, No 3, (1987) p267-27
3) has been performed, and it has been noted that increasing the discharge frequency higher than the conventional 13.56 MHz can improve the deposition rate without deteriorating the performance of the deposited film, and is drawing attention. Attempts to increase the discharge frequency have also been studied in sputtering and the like.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have used the conventional plasma CVD method and apparatus as described above, and have used a high frequency power having a frequency higher than 13.56 MHz for the purpose of improving the deposition rate of a good quality film. I examined it.

As a result, by increasing the frequency, it was possible to produce a good quality film at a higher deposition rate than the conventional one, but a new problem occurred. That is, by increasing the discharge frequency, the plasma becomes ubiquitous and the deposition rate becomes non-uniform, and as a result, in a relatively large-area workpiece such as an electrophotographic photoreceptor, a film that becomes a practical problem. Thickness unevenness (for example, film thickness unevenness of ± 20% or more in the case of electrophotographic photoreceptor) occurred.

Such film thickness unevenness is caused not only by the electrophotographic photoconductor but also by the crystalline or non-single crystalline functional deposited film used in the image input line sensor, the imaging device, the photovoltaic device and the like. It is also a big problem when forming. Also in other plasma processes such as dry etching and sputtering, similar process unevenness occurs when the discharge frequency is increased, which is a serious problem in practical use.

An object of the present invention is to overcome the above-mentioned conventional problems and to uniformly perform plasma processing on a relatively large-area substrate at a high processing speed which cannot be achieved by the conventional plasma processing. Another object of the present invention is to provide a different plasma processing apparatus and processing method.

[0012]

In a plasma apparatus of the present invention, a cathode electrode and a counter electrode facing the cathode electrode are provided in a depressurizable reaction vessel, and the cathode electrode has a high frequency power of 30 MHz or more and 300 MHz or less. A plasma processing apparatus which applies plasma by capacitive coupling via a matching circuit to generate plasma between the cathode electrode and the counter electrode, and performs plasma processing on a substrate to be processed arranged on the counter electrode, A soft magnetic material is arranged in a part of a high frequency transmission path between the cathode electrode and / or the matching circuit and the cathode electrode.

According to the plasma processing method of the present invention, plasma is generated between electrodes facing a cathode electrode to which high-frequency power is capacitively applied through a matching circuit in a reaction vessel capable of depressurizing, and the plasma is placed on the electrodes. In the plasma processing method of performing plasma processing on the substrate to be processed, a soft magnetic material is disposed in a part of the high frequency transmission path between the cathode electrode and / or the matching circuit and the cathode electrode, and the frequency of the high frequency power is set to 3
It is characterized by being set to 0 MHz or more and 300 MHz or less.

The cathode electrode has a cylindrical shape, and the substrate to be treated has a cylindrical shape.

The cathode electrode and the substrate to be treated are flat plates facing each other.

[0016]

The inventors of the present invention have made earnest studies on the above-mentioned problems in the conventional plasma processing apparatus and processing method. As a result, at a higher discharge frequency than the conventional one, the size of the apparatus becomes 1/10 or more of the high frequency wavelength. It was found that the effect of standing waves began to appear, resulting in uneven processing.

Experiments carried out to solve this problem and achieve uniform plasma and uniform plasma processing based thereon will be described below.

Using the apparatus shown in FIG. 5, the high frequency power output from the high frequency power supply 7 is applied and propagated on the cathode electrode 2 through the matching circuit 8, and the cathode electrode and the substrate 3 to be processed are opposed to each other. Plasma treatment was performed on the substrate to be treated by generating plasma with a high frequency electric field. At this time, the electrophotographic photosensitive member, which is the substrate to be treated, usually has a diameter of about 100 mm, and therefore the diameter d of the cathode is about 200 to 300 mm. When a high frequency wave is introduced from one point on the outer circumference of the cathode electrode, the distance to the opposite side of the outer circumference of the cathode electrode is 1.57d, which is about 390 mm when d = 250 mm.
For example, the frequency of high frequency is changed from the conventional 13.56 MHz to 1
At 00 MHz, the wavelength λ becomes about 22 m to 3 m in the atmosphere. That is, at 100 MHz, a high frequency wave introduced from one point on the outer circumference of the cathode electrode propagates on the outer circumference surface of the cathode electrode and reaches the opposite side, but the distance becomes λ / 10 or more and the influence of the standing wave causes the cathode electrode to move. An electric field distribution is generated on the outer circumference. The influence of this high-frequency electric field is further transmitted to the surface of the cathode electrode, causing unevenness of the electric field on the inner circumference of the cathode electrode, and uneven discharge occurs in the circumferential direction.

As described above, it has been found that the discharge frequency becomes higher at 13.56 MHz and its vicinity, but the discharge unevenness becomes remarkable by increasing the discharge frequency.

In order to measure from which frequency these problems become remarkable, the plasma CVD apparatus shown in FIG.
Discharge was performed at 3.56 MHz to 300 MHz, and each plasma density unevenness was measured. Here, the plasma density unevenness is defined as a value obtained by dividing the difference between the maximum value and the minimum value of the plasma density by the average value of the plasma density. As a result, it was shown that the plasma density unevenness was ± 10% or more in the vicinity of 30 MHz, and the unevenness of the high frequency voltage on the cathode electrode due to the discharge frequency became remarkable.

On the other hand, it has been found that if the frequency exceeds 300 MHz, it becomes difficult to design a high-frequency matching circuit and the transmission loss increases, which is not practical.

When the width of the energy of the ions incident on the substrate to be processed was measured, it was about 3 at 13.56 MHz.
It was about 15 eV at 0 eV and 30 MHz, and about 10 eV at 100 MHz and above. In the process of utilizing the ion energy incident on the substrate to be processed, it is important to reduce the energy width from the viewpoint that the controllability can be improved, and it is preferable to use a frequency of 30 MHz or higher. Therefore, it is extremely important to eliminate the unevenness of the plasma frequency density in this frequency range.

Therefore, the inventors of the present invention have obtained the following knowledge as means for solving the non-uniformity due to the high frequency voltage unevenness on the cathode electrode at 30 MHz to 300 MHz.

In order to prevent the high-frequency standing wave that causes the high-frequency voltage unevenness on the cathode electrode from being reflected in the plasma intensity unevenness, it is necessary to prevent the standing wave from occurring on the surface of the cathode electrode in contact with the plasma. Is.

In the apparatus of FIG. 5, in order to supply the high frequency power to the plasma, the high frequency power supplied from the high frequency power source is impedance-adjusted by a matching circuit so as to match the impedance of the plasma, and is introduced to the back surface of the cathode electrode. To do. Further, the high frequency is transmitted from the back surface of the cathode electrode to the surface of the cathode electrode in contact with the plasma through the skin of the cathode electrode, and the high frequency power is supplied to the plasma. Here, in order to prevent the high frequency power from being uneven on the surface of the cathode electrode, (a) the standing wave is not generated on the back surface of the cathode electrode, and (b) the strength of the standing wave generated on the back surface of the cathode electrode. It is effective to adjust the high frequency propagating to the cathode surface according to the above.

In order to easily and effectively carry out the above (a) and (b) at a higher frequency of 30 to 300 MHz, which is higher than the conventional frequency, a high permeability is provided in the back surface of the cathode and / or a part of the high frequency transmission path to the cathode. It was found that a soft magnetic material having magnetic susceptibility should be used. Here, the high frequency transmission line is
For example, a rod, plate or wire made of a good conductor such as copper that connects the matching circuit and the cathode,
The impedance can be easily changed by using a soft magnetic material for a part thereof.

The magnetic material having a large magnetic permeability acts so as not to allow a high frequency magnetic field to enter the inside thereof, and as a result, the skin effect becomes large, and the skin thickness to which high frequency can penetrate is extremely small as compared with the non-magnetic material. As a result, the impedance with respect to the high frequency increases, which hinders the transmission of the high frequency. Moreover, since high frequencies transmit only on the metal surface and do not penetrate inside the metal, it suffices to use a magnetic material only on the metal surface. The back surface of the cathode and / or a part of the surface of the high frequency transmission path to the cathode is coated with the magnetic material. It is enough to do or paste, and the pattern can be adjusted arbitrarily.
However, when a permanent magnet is used as the magnetic material, care must be taken because plasma may be unevenly distributed due to the magnetic field, and the soft magnetic material is most preferable.

The high-frequency insulating portion can be formed by using such a magnetic material, and the impedance can be arbitrarily changed.
Therefore, depending on the pattern, (1) a large number of high-frequency reflecting surfaces are formed at a distance sufficiently shorter than λ / 10 to prevent standing waves from being generated. (2) Standing waves on the back surface of the cathode are generated at high frequencies. It is possible to change the ratio of the high frequency wave transmitted to the cathode surface according to the voltage.

As described above, 30 to 300 MH
Uniform plasma can be obtained even at a high frequency of z, and a large-area plasma treatment can be performed at high speed and uniformly.

Although the plasma CVD has been described above, it is needless to say that the present invention is not limited to the plasma CVD and can be suitably applied to other plasma processing processes such as sputtering and etching.

[0031]

The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these examples.

(Embodiment 1) A discharge frequency of 100 MHz was obtained by using the cylindrical coaxial plasma CVD apparatus of the present invention shown in FIG.
z is an a-Si film under the film forming conditions shown in Table 1
Formed on.

A permalloy sheet 12 was attached to the outer periphery of the cathode 2 in the pattern shown in FIG. Although permalloy is used as the soft magnetic material, the soft magnetic material is not limited to this and any soft magnetic material may be used. If the film forming conditions are different, it may be necessary to change the pattern of the soft magnetic material accordingly, and the same effect may be obtained even if the pattern is completely different. Therefore, the pattern is not limited to the pattern of FIG. .

The film thickness unevenness in the circumferential direction when the film was formed in the pattern of FIG. 2 was measured. For comparison, when the soft magnetic material was not used and when the soft magnetic material was adhered to the entire circumference of the cathode, film formation was performed under the film forming conditions shown in Table 1 and the film thickness unevenness in the circumferential direction was measured. .

As a result, the film thickness unevenness was about ± 5% when the soft magnetic material was attached to a part of the outer circumference of the cathode, and about ± 30% when the soft magnetic material was not used. When the soft magnetic material was attached to the entire outer circumference of the cathode, the reactance of the cathode was too large to generate plasma, and film formation was impossible.

For each film, the film quality of the a-Si film was partially measured under the condition of the same film thickness, and it was found that the film quality was sufficient for practical use such as electrophotographic photosensitive device and image input line sensor. Met.

As described above, by using the soft magnetic material in a part of the outer circumference of the cathode electrode, the complex impedance at high frequency can be increased, and the high frequency line can be controlled only in the portion without the soft magnetic material. By configuring the device, it is possible to solve the problem of film thickness unevenness due to a higher discharge frequency. Further, the optimization of the device depending on the discharge frequency can be achieved by the shape and arrangement of the soft magnetic material.

[0038]

[Table 1] (Embodiment 2) Parallel plate type plasma C of the present invention shown in FIG.
Using a VD apparatus, an a-Si film was formed on the film formation base under the film formation conditions shown in Table 2 at a discharge frequency of 100 MHz.

In the present embodiment, a substrate having a square shape and a cathode electrode having a square plate shape were used. When a rectangular cathode is used, the distance from the position where the high frequency is introduced into the cathode electrode is different between the sides of the square and the corner, and the film thickness distribution is likely to occur.
A permalloy sheet 12 having a pattern shown in FIG. 4 was attached to the back surface of the rectangular cathode electrode. Although permalloy is used as the soft magnetic material, any soft magnetic material may be used. When the film forming conditions are different, it may be necessary to modify the pattern of the soft magnetic material accordingly, and the same effect may be obtained even if the pattern is completely different. Therefore, the pattern is not limited to the pattern of FIG. .

The film thickness unevenness when the film was formed in the pattern of FIG. 4 was measured. Further, under the same film forming conditions, a comparative experiment was performed on the unevenness of the film thickness in the circumferential direction between the case where the soft magnetic material was not used and the case where the soft magnetic material was entirely attached to the outer circumference of the cathode. As a result, the film thickness unevenness is about ± 10% when the soft magnetic material is attached to a part of the outer circumference of the cathode, and about ± 30% when the soft magnetic material is not used.
Became. When the soft magnetic material was attached to the entire outer circumference of the cathode, the reactance of the cathode was too large to generate plasma and film formation was impossible.

When the film quality of the a-Si film was partially measured in the same film thickness condition for each film, the film quality was sufficient for practical use such as electrophotographic photosensitive device and image input line sensor. there were.

[0042]

[Table 2]

[0043]

According to the present invention, that is, 30 MHz or more,
By using a high frequency of 300 MHz or less and arranging a soft magnetic material in a part of the high frequency transmission path between the cathode electrode and / or the matching circuit and the cathode electrode, a uniform high frequency discharge is achieved, and a large area substrate is processed. Can be processed uniformly and at high speed.

[Brief description of drawings]

FIG. 1 is a plasma C having a cylindrical cathode electrode of the present invention.
It is a structural schematic diagram which shows an example of a VD apparatus.

FIG. 2 is a schematic diagram showing an example of a cathode electrode used in the plasma CVD apparatus of the present invention.

FIG. 3 is a plasma C having a flat cathode electrode according to the present invention.
3 is a schematic configuration diagram showing an example of a VD device.

FIG. 4 is a schematic diagram showing an example of a cathode electrode used in the plasma CVD apparatus of the present invention.

FIG. 5 is a schematic configuration diagram showing a conventional plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 reaction container, 2 cathode electrode, 3 substrate for film formation, 4 substrate holder, 5 heater, 6 earth shield, 7 high frequency power supply, 8 matching circuit, 9 vacuum evacuation means, 10 gas supply means, 11 insulating material, 12 soft Magnetic material.

Claims (8)

[Claims] 1. A cathode electrode and a counter electrode facing the cathode electrode are provided in a depressurizable reaction vessel, and high frequency power of 30 MHz or more and 300 MHz or less is applied to the cathode electrode by capacitive coupling through a matching circuit. A plasma processing apparatus for generating plasma between the cathode electrode and a counter electrode to perform plasma processing on a substrate to be processed arranged on the counter electrode, wherein the cathode electrode and / or the matching circuit and the cathode are provided. A plasma processing apparatus characterized in that a soft magnetic material is arranged in a part of a high-frequency transmission path between electrodes. 2. The plasma processing apparatus according to claim 1, wherein the cathode electrode has a cylindrical shape. 3. The plasma processing apparatus according to claim 1, wherein the substrate to be processed has a cylindrical shape. 4. The plasma processing apparatus according to claim 1, wherein the cathode electrode and the substrate to be processed are flat plates facing each other. 5. A plasma is generated between electrodes facing a cathode electrode to which high-frequency power is applied by capacitive coupling through a matching circuit in a depressurizable reaction container, and a plasma is generated on a substrate to be processed arranged on the electrodes. In a plasma processing method for performing plasma processing, a soft magnetic material is arranged in a part of a high frequency transmission path between a cathode electrode and / or a matching circuit and the cathode electrode, and a frequency of the high frequency power is 30 MHz or more and 300 MHz or less. And a plasma processing method. 6. The plasma processing method according to claim 5, wherein the cathode electrode has a cylindrical shape. 7. The plasma processing method according to claim 5, wherein the substrate to be processed has a cylindrical shape. 8. The plasma processing method according to claim 5, wherein the cathode electrode and the substrate to be processed are flat plates facing each other.