JP2609866B2 - Microwave plasma CVD equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a deposited film on a substrate, especially a functional film, particularly a semiconductor device, an electrophotographic photosensitive member device, an image input line center, an imaging device, and light. The present invention relates to a microwave plasma CVD apparatus for forming a functional thin film used for an electromotive device or the like.

[Description of Prior Art]

Conventionally, semiconductor devices, photoreceptor devices for electrophotography,
Line sensors for image input, imaging devices, photovoltaic devices, other various electronic elements, optical elements,
Amorphous silicon,
For example, amorphous silicon (hereinafter referred to as “A-Si”) compensated with hydrogen and / or halogen (eg, fluorine, chlorine, etc.)
(H, X)]. ) Have been proposed, and some of them have been put to practical use.

And such a deposited film is a plasma CVD method, that is,
It can be formed by a method in which a raw material gas is decomposed by direct current, high frequency, or microwave glow discharge to form a thin deposited film on a support such as glass, quartz, a heat-resistant synthetic resin film, stainless steel, or aluminum. It is known, and various apparatuses have been proposed.

Especially, plasma using microwave glow discharge decomposition in recent years
The CVD method has been attracting industrial attention.

And as a microwave plasma CVD apparatus, so-called ECR
Several (electron cyclotron resonance) type plasma CVD apparatuses have been reported, but none of these apparatuses basically excites the source gas directly.

On the other hand, a microwave plasma that generates microwave plasma by supplying microwave power directly to the raw material gas
CVD equipment has been developed and has entered the realm of practical use.

FIG. 3 is a schematic cross-sectional view schematically showing an example of a microwave CVD apparatus of the latter type, which has been developed by the present inventors and put to practical use.

In FIG. 3, 301 is a microwave introduction part, 302 is a vacuum vessel, 303 is a support (cylindrical) (when the support is plate-shaped, a cylindrical support, for example, the surface of an aluminum cylinder) The plate-shaped support is brought into close contact with the substrate so that a deposited film is formed.
Is an exhaust buffer plate, 306 is a vacuum seal mechanism, 307 is a cooling system introduction part, 308 is a support rotation motor, 309 is a support rotation shaft, 310 and 311 are support holders, 312 is plasma, and 31
Reference numeral 3 denotes microwave introduction windows.

In the apparatus shown in the figure, a support 303 (for example, an aluminum cylinder) is arranged so as to form an apparent cylindrical space in a vacuum vessel 302, and at least one end face of the cylindrical space is used to form the inside of the vacuum vessel 302. It has a quasi-circular cavity resonator structure in which microwave power is applied to the other end face of the cylindrical space to generate a discharge therein, and the microwave introduction unit 301 is provided with the aforementioned ECR (Electron Cyclotron). There is no need to provide a large electromagnet coil or ECR cavity as in a (resonance) type device, it can be designed relatively simply, and the vacuum vessel 302 or its internal structure acts as a cavity resonator. Because it can supply more power than an ECR type plasma CVD apparatus, the deposition rate is relatively high and the gas decomposition rate is close to 100%. Formation and mass production Suitable has an advantage.

The operation of forming a deposited film by the apparatus shown in FIG. 3 is performed as follows.

First, a support (Al cylinder) 303 is placed in a vacuum vessel 302.
The support 303 is rotated by a support rotating motor, and the pressure is reduced to about 10 ⁻⁶ Torr or less by a diffusion pump (not shown). Subsequently, the temperature of the support is controlled to a predetermined temperature of 50 ° C. to 400 ° C. by the support heating motor 304. When the temperature of the support 303 reaches a predetermined temperature, a gas cylinder (not shown)
When a predetermined gas, for example, an A-Si (H, X) film is formed from the above, a source gas such as a silane gas or a hydrogen gas is introduced into the discharge space A via a gas introduction pipe. Then, the internal pressure of the discharge space A is set to a predetermined pressure of 10 mTorr or less. After the internal pressure stabilizes, a microwave power source (not shown)
A microwave of 0 MHz or more, preferably 2.45 GHz, is generated, and microwave energy is introduced into the discharge space A via the microwave introduction unit 301 and the microwave introduction window 313.

Thus, the source gas in the vacuum vessel is decomposed by the energy of the microwave, and a deposited film is formed on the support 303.

However, in this apparatus, although the gas decomposition efficiency is high as described above, that is, the plasma energy is large, the temperature of the surface of the support facing the plasma rises during film formation. In some cases, unexpected problems such as deterioration of film quality and occurrence of structural hysteresis may occur. In some cases, it is necessary to limit the microwave input power during film formation.

In addition, it has been proposed to take measures such as cooling to a certain extent to prevent the temperature from rising so as not to exceed the upper limit of the set heating temperature of the support during film formation.

However, the fact is that the effect is not necessarily sufficient by any of them.

[Object of the invention]

The object of the present invention is, by a microwave plasma CVD method,
Uniform, high-quality, highly reproducible deposition when forming deposited films as element members used for semiconductor devices, electrophotographic photoreceptor devices, photovoltaic elements, other various electronic elements, optical elements, etc. An object of the present invention is to provide an apparatus capable of forming a film stably.

[Configuration of the invention]

The present inventors have solved the above-mentioned problems in the conventional microwave plasma CVD apparatus in which microwaves are directly introduced into a vacuum vessel, and conducted intensive research to achieve the above-mentioned objects. A magnet is placed at the outer periphery of the introduction part and at a position opposite to it, and a closed magnetic field is formed in the space formed by both magnets to increase the plasma density in the central part of the discharge, thereby lowering the plasma density in the vicinity of the support and supporting it. We have obtained knowledge that can prevent overheating of the body surface.

The present invention has been completed based on this finding.
The microwave plasma CVD apparatus of the present invention includes a vacuum vessel having a discharge space therein, a means for supplying a source gas into the vacuum vessel, a means for exhausting the inside of the vacuum vessel, and at least one side of the vacuum vessel. And a microwave introduction unit for introducing microwave power into the discharge space of the vacuum vessel, and a support for forming a deposited film provided around the discharge space in the vacuum vessel. Means and a closed magnetic field is formed in a direction along the surface of the support that is held by the holding means to reduce the plasma density at the surface of the support or to move the plasma away from the surface of the support. As described above, a magnet is provided at a position sandwiching the holding means and at the outer periphery of the microwave introduction portion and at a position facing the outer periphery of the microwave introduction portion.

In the microwave plasma CVD apparatus of the present invention, the magnets arranged at the outer periphery of the microwave introduction portion and at positions facing the microwave introduction portion may have a constant magnetic force or may be electromagnets. If necessary, a magnetic shield can be provided on the magnet in order to avoid a magnetic influence outside the device.

Further, in the microwave CVD device of the present invention, the device components other than the magnet are formed of a non-magnetic material, and the device components are arranged so as not to affect the magnetic field, or a size satisfying such conditions. It is desirable to make.

The source gas used to form the deposited film with the apparatus of the present invention may be of the type that excites by microwave energy and chemically interacts to form the desired deposited film on the substrate surface. Any material can be used, for example, in the case of forming an A-Si (H, X) film, silanes and halogens in which hydrogen, halogen, hydrocarbon, or the like is bonded to silicon are used. For example, a gas such as silane silicide, hydrogen gas, or a mixed gas of hydrogen gas and argon gas can be used. Further, the film of A-Si (H, X) can be doped with a p-type impurity element or an n-type impurity element, and the source gas containing these impurity elements as constituent components is the same as the source gas described above. They can be used in combination.

The support may be conductive, semiconductive, or electrically insulating, and specifically includes metal, ceramics, and glass. . The substrate temperature during the film forming operation is not particularly limited, but is generally in the range of 30 to 450 ° C., preferably 50 to 350 ° C.

In forming a deposited film, the pressure in the plasma chamber and the film forming chamber is set to 5 × 10 ⁻⁶ To before the source gas is introduced.
rr or less, preferably 1 × 10 ⁻⁶ Torr or less, and when the source gas was introduced, the pressure was 4 × 10 ⁻⁴ to 2 × 10 ⁻³ Torr, preferably 8 × 10 ⁻⁴ to 1 × 10 ⁻³ Torr. It is desirable to do.

Hereinafter, the present invention will be described in more detail with reference to specific device examples, but the present invention is not limited thereto.

Apparatus Example 1 A specific example of a microwave plasma CVD apparatus capable of achieving the object of the present invention is shown in a schematic longitudinal section in FIG. 1 and a schematic sectional view in FIG.

1 and 2, reference numeral 1 denotes a microwave introduction window,
2 is a microwave introduction window holding cylinder, 6 is a magnet, 7 is a vacuum vessel, 8 is an exhaust buffer plate, 9 is a support, 10 is a heater for heating the support, 11 and 12 are support holders, and 13 is a support. Rotation axis, 14 is a vacuum seal mechanism, 15 is a cooling system introduction part, 16 is a support rotating motor, 17, 18 are base flanges, 19 is plasma, 20 is a region with high plasma density, 21 is a waveguide, 22 Denotes a magnet holder, and 201 denotes a cooling jacket.

In the device of this example, a plurality of cylindrical supports 9, 9, ... are arranged in a ring in a vacuum vessel, and microwave discharge is performed by using a space surrounded by the supports 9, 9, ... as a pseudo cavity resonator. This is a direct introduction type microwave CVD device, in which the entire length of the support 9 is long,
Since it is necessary to form a film uniformly on the surface of the support 9, the microwave introduction window 1, the microwave introduction window 1 above and below the vacuum vessel 7 are provided so that microwave discharge power can be introduced from both ends of the support 9. The wave introduction window holding cylinder 2 and the waveguide are installed. A magnet 6 is arranged on the outer periphery of each microwave introduction window so as to form a closed magnetic field between the two magnets.

Formation of a deposited film using the apparatus shown in FIGS. 1 and 2 is performed as follows.

First, a plurality of cylindrical supports 9 are arranged in an annular shape in the vacuum vessel 7, the support 9 is rotated by a support rotating motor 16, and the inside of the vacuum vessel 7 is evacuated to 10 ⁻⁶ Torr or less. Subsequently, the temperature of the support is set to 50 by the heater 10 for heating the support.
It is heated to a predetermined temperature of 400 to 400 ° C. and kept at the predetermined temperature. In this case, silane gas (SiH ₄ ) and hydrogen gas (H ₂ ), which are source gases for forming an A-SiH film, are introduced into the vacuum vessel 7, and the pressure in the vacuum vessel is reduced to a predetermined pressure of 10 mTorr or less. To control. Where the internal pressure is stable,
Microwaves (2.45 GHz) are introduced from both ends of the vacuum container 7 into the container via the microwave introduction window 3, the microwave incident power and the reflected power are appropriately adjusted, and are surrounded by a plurality of cylindrical supports 9. Glow discharge plasma is generated in the discharge space A.

Since a closed magnetic field is formed between the microwave introduction windows 3 in the discharge space A, the electrons emitted by the decomposition of the source gas in the plasma are confined in this magnetic field and collide with other source gas molecules. Then, new electrons are emitted, and the phenomenon occurs continuously in the plasma to which the magnetic field is applied. Therefore, the plasma density increases in the central portion 20 of the discharge space A, that is, in the space to which the magnetic field is applied. . Fig. 4
It is a schematic diagram which shows the state of the generated magnetic field in the apparatus shown in the figure, where 401 is a magnet, 402 is a line of magnetic force, 403 is an electron emitted by gas decomposition, and 404 and 405 are motion trajectories of an electron 403 constrained in the magnetic field. Is shown.

As a result, the plasma density is reduced on the surface of the support 9 or the plasma is separated from the surface of the support 9 and only electrically neutral active radical species fly on the surface of the support 9. Thus, an excessive rise in temperature on the surface of the support can be prevented, and the film formation always proceeds under stable temperature conditions.

Apparatus Example 2 FIG. 5 is a schematic view showing another embodiment of the microwave CVD apparatus of the present invention, and FIG. 6 is a sectional view taken along line XX ′ of FIG. In the figure, 501 is a microwave introduction part, 502 is a support, 503 is a support holder, 504 is a metal mesh, 505 is a gas exhaust hole, 506 is an exhaust buffer plate, 507 is a vacuum vessel, 508
Is a heater for heating the support, 509 is a vacuum seal mechanism, 510 is a motor for rotating the support, 511 is a rotating shaft, 512 is a magnet, 513,
Reference numerals 514 denote end plates, respectively.

As shown in FIG. 5, the apparatus of this embodiment is an example of a direct introduction type microwave CVD apparatus for a long flat support having only one microwave introduction section, and is provided at the upper end of a vacuum vessel 507. Magnets 512 are provided on the outer periphery of the microwave introduction unit 501 and the lower end of the vacuum vessel, respectively, to form a closed magnetic field.

Next, the effects of the present invention will be specifically described using test examples of deposition film formation by the apparatus of the present invention.

Test Example A-A film was formed on a cylindrical Al substrate under the conditions shown in Table 1.
A Si: H film was deposited to a thickness of about 12 μm. As a comparative example, an A-Si: H deposited film was formed under the same film forming conditions except that no magnetic field was applied. Then, the temperature, film thickness distribution, S / N ratio and deposition rate of the substrate surface were measured for each. The results are shown in FIG. 7 and Table 2.

FIG. 7A shows the relationship between the film formation time and the substrate surface temperature, and FIG. 7B shows the film thickness distribution at the measurement position of the substrate. Table 2 shows the measurement results of the SN ratio and the deposition rate.

As shown in FIG. 7, it was confirmed that the application of the magnetic field reduced the plasma density near the surface of the substrate, and suppressed the temperature rise on the surface of the substrate.

[Effects of the Invention] In the microwave plasma CVD apparatus of the present invention, a magnet is arranged at the outer periphery of the microwave introduction part and at a position opposed thereto, and by forming a closed magnetic field, the temperature of the support surface is increased due to plasma exposure. Can be suppressed, and film formation can be performed under stable temperature conditions, so that a high-quality deposited film can be constantly mass-produced over a large area.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a typical example of a microwave plasma CVD apparatus of the present invention, and FIG. 2 is a sectional view taken along line XX of FIG. FIG. 3 shows a conventional microwave plasma CVD.
FIG. 4 is a schematic sectional view showing an example of the apparatus, and FIG. 4 is a view schematically showing a state of a generated magnetic field in the microwave CVD apparatus of the present invention. FIG. 5 is a schematic sectional view showing another example of the microwave CVD apparatus of the present invention, and FIG. 6 is a sectional view taken along line XX of FIG. FIG. 7 (A) is a diagram showing the temperature of the substrate surface when the apparatus shown in FIG. 1 is used.
FIG. 2B is a diagram showing a film thickness distribution when the apparatus shown in FIG. 1 is used. In FIGS. 1 and 2, 1... Microwave introduction window, 2... Microwave introduction window holding cylinder, 6... Magnet, 7.
8: exhaust buffer plate, 9: support, 10: heater for heating the support, 11, 12, support holder, 13: rotating shaft of the support, 14: vacuum sealing mechanism, 15 ... Cooling system introduction,
16 ... Motor for rotating the support, 17,18 ... Base flange, 19 ... Plasma, 20 ... Plasma with high plasma density,
21: waveguide, 22: magnet holder, 201: cooling jacket, A: discharge space. In FIG. 3, 301... Microwave introduction part, 302... Vacuum container, 303... Support, 304.
307 ... Cooling system introduction part, 308 ... Support body rotation motor,
309… Support rotating shaft, 310, 311… Support holder, 312
…… Plasma, 313 …… Microwave introduction window, A …… Discharge space. In FIG. 4, reference numerals 401... Magnet, 402.
... Emitted electrons due to gas decomposition, 404,... Movement locus of the electrons 403 confined in the magnetic field, A... Discharge space. In FIGS. 5 and 6, 501... Microwave introduction part, 502.
Support, 503 ... Support holder, 504 ... Metal mesh,
505 …… Gas exhaust hole, 506 …… Exhaust buffer plate, 507 ……
Vacuum container, 508: Heater for heating the support, 509: Vacuum sealing mechanism, 510: Motor for rotating the support, 511: Rotating shaft of the support, 512: Magnet, 513, 514: End plate.

Claims (1)

(57) [Claims] 1. A vacuum vessel having a discharge space therein, means for supplying a source gas into the vacuum vessel, means for evacuating the vacuum vessel, and a part provided on at least one side of the vacuum vessel. A microwave introduction unit for introducing microwave power into the discharge space of the vacuum vessel, a means for holding a deposited film forming support provided around the discharge space in the vacuum vessel, and So that a closed magnetic field is formed in a direction along the surface of the support that is held by the holding means to reduce the plasma density at the surface of the body or to move the plasma away from the surface of the support; A microwave plasma CVD apparatus, comprising: magnets disposed at positions sandwiching the holding means, at the outer periphery of the microwave introduction part and at positions opposed thereto.