JP2899254B2 - Plasma CVD equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method for generating a high-energy excited species by applying a magnetic field to form a large and uniform thin film while etching. It concerns the device. 2. Description of the Related Art Conventionally, electron cyclotron resonance (ECR) has been used as a means for forming a thin film, and a substrate is disposed at a position "distant from the resonance space" by utilizing the divergent magnetic field.
There is known a method of forming a film there, particularly a film having an amorphous structure. Furthermore, generally, in addition to such electron cyclotron resonance CVD (chemical vapor deposition),
Several types of film forming means using a reactive gas are known. These film forming means include, for example, heat
CVD, heated filament CVD, chemical transport method, a plasma CVD method using a frequency of 13.56MH _z, plasma CVD method using only microwaves are known. [0003] In particular, the electron cyclotron resonance CVD method,
The active species are pinched by a magnetic field to increase the energy, thereby increasing the electron energy and efficiently converting the reactive gas into plasma. However, in the electron cyclotron resonance CVD method, a reactive gas is turned into plasma, and the film forming surface of the substrate is sputtered (damaged) by the high energy of the reactive gas. In order to prevent this sputtering, the electron cyclotron resonance CVD method uses a substrate placed at a position "far away" from the space that satisfies the electron cyclotron resonance conditions, and ion showering that avoids the plasma state under high energy conditions Film formation or anisotropic etching has been performed by allowing the reactive gas to reach the substrate surface. [0004] However, in such a method of forming a film using a showered reactive gas, anisotropic etching, etching such as formation of a film having an amorphous structure, or etching, depending on the type of the gas, is required. Only one of the deposition processes was adopted. Therefore, a film having an amorphous structure is easily formed on the film-formed surface in this case, and it has been extremely difficult to form a film having crystallinity, particularly, polycrystalline or single crystal.
In addition, in the method of forming a film using the showered reactive gas, the energy is weakened in order to prevent sputtering. Therefore, the activation or reaction of the reactive gas is performed only by using a high energy. It was not possible to form a coating that could cause An object of the present invention is to provide a plasma CVD apparatus in which a substrate having a film forming surface is arranged in a plasma space and a magnetic field is applied to a reactive gas to form a film while etching. And In order to achieve the above object, a plasma CVD apparatus according to the present invention comprises a plasma generation space, a gas introduction system for introducing a reaction gas into the plasma generation space, and a plasma generation system. An electron cyclotron resonance having a microwave generator for introducing a microwave through a window into a generation space is used, and the electron cyclotron resonance is generated in the plasma generation space substantially parallel to the microwave propagation direction. Means for generating a strong magnetic field, exhaust means for adjusting the reaction pressure in the plasma generation space, and, in the plasma generation space, the strength of the magnetic field decreases toward the substrate in the microwave propagation direction. And a means for arranging the substrate on a uniform magnetic field surface. The plasma CVD apparatus of the present invention has a plasma generation space, a gas introduction system for introducing a reaction gas into the plasma generation space, and a microwave generator for introducing a microwave through the window into the plasma generation space. Means for using electron cyclotron resonance, while forming a microwave standing wave in the plasma generation space, means for generating the standing wave to have a maximum value in the plasma generation space, A means for generating a magnetic field, which is substantially parallel to the direction of propagation of the microwaves, and which is strong enough to cause electron cyclotron resonance in the plasma generation space; and an exhaust means for adjusting a reaction pressure in the plasma generation space. in the plasma generating space, at a position where the intensity of the magnetic field toward the substrate in the propagation direction of the microwave decreases, or Characterized in that it comprises a means for positioning the substrate in the maximum area of the isomagnetic plane and a standing wave. The isomagnetic field in the plasma CVD apparatus of the present invention is approximately 875 Gauss. [0008] A plasma CVD apparatus according to the present invention comprises:
A plasma generation space, a gas introduction system for introducing a reaction gas, a microwave generator for introducing a microwave through a window to the plasma generation space, and substantially parallel to a microwave propagation direction, and in the plasma generation space. a magnetic field generating means for generating an electron cyclotron resonance, and exhaust means for adjusting the reaction pressure of the plasma generation space, wherein the plasma
Means for arranging the substrate at a position where the intensity of the magnetic field decreases in the propagation direction of the microwave in the microwave generation space and on the isomagnetic field surface. [0009] The microwave generated from the microwave generator propagates toward the substrate. Further, the magnetic field generating means for generating a magnetic field, the direction of the magnetic field perpendicular to the equal magnetic field,
The direction of propagation of the generated microwave is substantially parallel and the intensity is such that electron cyclotron resonance is generated (see FIG. 2A). In addition, the substrate is empty
In the microwave propagation direction, it is arranged at a position where the strength of the magnetic field decreases toward the substrate in the microwave propagation direction (FIG. 2).
(A)). Further, the microwave generated from the microwave oscillator becomes a standing wave (see FIG. 2B) in the closed plasma generation space , and the substrate is disposed at a position where the electric field has a maximum value. An electric field intensity is applied to the film forming surface of the substrate on which the film is formed. When the intensity of the magnetic field in the region is adjusted, the reactive gas can be decomposed or reacted only in this region for the first time, and a film is formed on the substrate while being etched. The film formed on the substrate in this manner is, for example, an i-carbon film (diamond or a carbon film having fine crystal grains), a high-melting metal film, or a ceramic insulating film. That is, the present invention applies a magnetic field to a conventionally known plasma CVD method using microwaves to generate high-density, high-energy plasma in a wide pressure range. The reaction space in a reduced pressure state utilizes a high energy state to generate a large amount of activated carbon atoms, for example, and has excellent reproducibility, a uniform thickness, uniform characteristics of a diamond film, i-carbon. This enables the formation of a film such as a film. Further, the present invention provides a method for applying a DC bias voltage to a high-energy excited species generated by the action of a magnetic field,
When etching and film formation are performed simultaneously, a large amount of excitons reach the substrate side, thereby improving the thin film formation speed. Further, in addition to the configuration of the present invention, light having a high energy (for example, ultraviolet light) is irradiated while reaching the substrate surface,
When energy is continuously applied to the active species, carbon atoms excited to a high energy state exist even at a position sufficiently distant from the high-density plasma generation region, and a diamond film and an i-carbon film are formed in a larger area. It is also possible. Further, the present invention can also generate high-density plasma by the interaction between a microwave and a magnetic field. FIG. 1 is a view for explaining a microwave plasma CVD apparatus capable of applying a magnetic field according to an embodiment of the present invention. In FIG. 1, the microwave plasma CVD apparatus is
A plasma generation space (1) capable of maintaining a reduced pressure, an auxiliary space (2), a heating space (3), a microwave oscillator (4),
Electromagnets (5), (5 ') that generate a magnetic field, and a gas introduction system (6),
(7), a turbo molecular pump (8) constituting an exhaust system, a substrate (10), a substrate holder (10 '), and a pressure regulating valve (11)
And a rotary pump (14) and a microwave introduction window (15)
, Water cooling system (18), (18 '), infrared heating heater (20), infrared reflecting surface (21), lens system (22), power supply (23), power supply (2
5). First, the substrate (10) for forming a thin film is a substrate holder.
(10 ') Installed on top. The substrate holder (10 ') was made of ceramic aluminum nitride in order to have high thermal conductivity and to disturb microwaves as little as possible. This substrate holder (10 ') is a lens system in which infrared rays emitted from an infrared heating heater (20) are an infrared reflecting surface (21).
The light is condensed through (22), and is heated at, for example, 500 ° C. Next, into the plasma generation space (1), hydrogen was introduced from the gas introduction system (6), and methane (CH ₄ ) or acetylene (C ₂ H ₂ ) was introduced from the gas introduction system (7). A microwave of a frequency of 2.45 GHz is applied at an intensity of 500 W. Further, a magnetic field of about 2K Gauss is applied to the plasma generating space (1) by the electromagnets (5) and (5 ') to generate high density plasma. At this time, the plasma generation space (1)
Is maintained at 0.1 Pa. Hydrogen atoms or electrons having higher energy than the high-density plasma region reach the substrate (10) and clean the surface of the substrate. Further, after the introduction of hydrogen was stopped, a carbide gas introduced from the gas introduction system (7), for example, methane (CH ₄ ), acetylene (C ₂ H
₂ ) Activate. Then, carbon atoms excited to high energy are generated, and the above-described carbon atoms are deposited on the substrate (10) heated at about 500 ° C. by the infrared heater (20), and diamond or i-carbon is deposited. A film is formed. In FIG. 1, a Helmholtz coil system using two ring-shaped electromagnets (5) and (5 ') is employed as a magnetic field. FIG. 2 shows the results of examining the electric and magnetic field strength in the space (30) obtained by dividing the plasma generation space (1) into four parts. FIGS. 2A and 2B are diagrams for explaining magnetic field and electric field characteristics by computer simulation in the film forming apparatus shown in FIG. 1 which is one embodiment of the present invention. It should be noted that the electromagnet (5) and the electromagnet (5 ') on the central axis of the electromagnet (5) and the electromagnet (5') in FIG.
The midpoint of is the origin. In FIG. 2A, the horizontal axis (X
The axis (axis) is the lateral direction (reactive gas emission direction) of the plasma generation space (1), and the vertical axis (Y axis) is the radial direction of the electromagnets (5) and (5 '). The curve in FIG. 2A shows the equipotential surface of the magnetic field. And the number shown on that line is
It shows the strength of the magnetic field obtained when the electromagnet (5) is about 2000 Gauss. By adjusting the strength of the electromagnet (5), it is possible to make the strength of the magnetic field approximately uniform over a large area of the surface on which the substrate is formed in the space (100) (875 ± 185 Gauss) where electric and magnetic fields interact. it can. In FIG. 2A,
For example, an iso-magnetic surface that produces an electron cyclotron resonance (ECR) condition where line (26) is 875 Gauss. Further, the space (100) where the electron cyclotron resonance condition occurs is set to be a region where the electric field is maximum as shown in FIG. 2 (B). The horizontal axis of FIG. 2 (B) indicates the direction in which the reactive gas flows as in FIG. 2 (A), and the vertical axis indicates the intensity of the electric field (electric field intensity). The electric field is
In addition to the space (100), the space (100 ') has a maximum area. However, the magnetic field of FIG. 2A corresponding thereto has an extremely large number of isomagnetic fields. That is, the space (10
0 ′) is in the radial direction of the surface to be formed on the substrate (10) (FIG. 2).
The variation in the film thickness (in the vertical axis direction in (A)) becomes large, and only a high-quality film is formed in a portion satisfying the electron cyclotron resonance condition indicated by reference numeral (26 ') in FIG. As a result, on the surface of the substrate (10),
A uniform and uniform coating cannot be expected. Of course, the board (1
If a coating is to be formed on the surface of 0) in the form of a donut, this may be the case. On the opposite side of the space (100) with its origin symmetrical, there is a region where the maximum electric field and the magnetic field are constant over a wide region. Board (10)
When it is not necessary to perform heating, it is effective to form a film in the above space. However, it is difficult to obtain a means for heating the substrate (10) without disturbing the microwave electric field. As a result of these,
Considering the ease of taking in and out of the substrate (10) and the ease of heating the substrate (10), in order to form a uniform film and a uniform film, the space (100) in FIG. ) Is estimated to be the most industrially superior in mass productivity among the three regions.
As a result, in the present invention, when the substrate (10) is disposed in the space (100), if the substrate (10) is circular, a radius of 100 mm
, Preferably up to a radius of 50 mm. Further, in order to increase the area, for example, to obtain the same uniform film thickness in an area four times larger than this, if the frequency is not 2.45 GHz but 1.225 GHz, the diameter of this space (R in FIG. 2A) Direction) can be doubled. FIG. 3 is a diagram for explaining the equal magnetic field and the equal electric field of the magnetic field (A) and electric field (B) in the circular space at the position of the substrate in FIG. As is clear from FIG. 3B, the electric field can reach a maximum of 25 KV / m. For comparison, a thin film was formed under the same conditions without applying a magnetic field. At that time, the thin film formed on the substrate (10) was a graphite film. Furthermore, when the temperature of the substrate (10) was set to 650 ° C. or higher under the same conditions as in this example, it was possible to form a diamond thin film.
When an electron beam diffraction image of the thin film formed in this example was taken, spots of diamond were observed together with halo patterns peculiar to amorphous, and an i-carbon film was formed. Further, as the temperature of the substrate (10) was raised to form a film, the halo pattern gradually disappeared and a diamond film was formed at 650 ° C. or higher. When the heating temperature of the substrate (10) was lower than 150 ° C., an i-carbon film could not be formed even when a magnetic field was applied. In such a method, a silicon carbide polycrystalline film can be formed on substrate (10) using silicide gas (methylsilane). An aluminum nitride film can also be formed by the reaction between an aluminum compound gas and ammonia. Further, a conductor having tungsten, titanium, and molybdenum as main components or a high-melting-point conductor of silicide thereof can be formed. According to the present invention, a reactive gas is introduced into a plasma generating space , a magnetic field is applied to the reactive gas from the outside, and high-energy excited species are generated by the action of the magnetic field. Since the film was formed while etching, a uniform thin film having a large area can be obtained. According to the present invention, in the plasma generation space , the substrate is arranged at a position where the strength of the magnetic field decreases toward the substrate in the microwave propagation direction, and the microwave generated from the microwave oscillator is a standing wave. Thus, by arranging at the position where the electric field has the maximum value, a thin film of good quality can be obtained. According to the invention, the coated surface of the substrate is approximately 875 ga
Since the thin film was disposed in a region having a uniform magnetic field called a mouse, it was possible to form a uniform thin film having a large area and to form a film having crystallinity at least partially. According to the present invention, the produced thin film was a good film having almost no film stress in both tension and compression.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a microwave plasma CVD apparatus to which a magnetic field can be applied in one embodiment of the present invention. FIGS. 2A and 2B are diagrams for explaining magnetic field and electric field characteristics by computer simulation in the film forming apparatus shown in FIG. 1, which is one embodiment of the present invention. FIG. 3 is a diagram for explaining an equal magnetic field and an equal electric field of a magnetic field (A) and an electric field (B) in a circular space at a position of a substrate in FIG. 2; [Description of Signs] 1... Plasma generating space 2... Auxiliary space 3... Heating space 4... Microwave oscillators 5 and 5 ′. 6, 7 ... gas introduction system 8 ... turbo molecular pump 10 ... substrate 10 '... substrate holder 11 ... pressure regulating valve 14 ... rotary pump 15 ・ ・ ・ Microwave introduction window 18, 18 ′ ・ ・ Water cooling system 20 ・ ・ ・ ・ ・ Infrared heating heater 21 ・ ・ ・ ・ ・ Infrared reflecting surface 22 ・ ・ ・ ・ ・ Lens system 23, 25 ・・ ・ Power supply 100 ・ ・ ・ ・ Space for maximum electric field

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/31 H01L 21/31 C (72) Inventor Shunpei Yamazaki 398 Hase, Atsugi-shi, Kanagawa Pref. Semiconductor Energy Laboratory Co., Ltd. (56) References JP-A-60-134423 (JP, A) JP-A-56-155535 (JP, A) Nikkei Microdevices Spring 1985 Special Edition (1985.2.4) 93-100 (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 16/50 C23C 16/26

Claims (1)

(57) [Claims] Plasma CVD using electron cyclotron resonance having a plasma generation space, a gas introduction system for introducing a reaction gas into the plasma generation space, and a microwave generator for introducing microwaves through a window to the plasma generation space
An apparatus for generating a magnetic field substantially parallel to a microwave propagation direction and having an intensity for generating electron cyclotron resonance in the plasma generation space; and for adjusting a reaction pressure in the plasma generation space. Exhaust means, and means for arranging the substrate at a position where the strength of the magnetic field decreases in the plasma generation space toward the substrate in the direction of propagation of the microwave, and on the isomagnetic field surface. A plasma CVD apparatus characterized by the above-mentioned. 2. The iso-magnetic surface is approximately 875 Gauss
The plasma CVD apparatus according to claim 1, wherein 3. Plasma CVD using electron cyclotron resonance having a plasma generation space, a gas introduction system for introducing a reaction gas into the plasma generation space, and a microwave generator for introducing microwaves through a window to the plasma generation space
In the apparatus, means for forming a standing wave of a microwave in the plasma generation space and generating the standing wave so as to have a maximum value in the plasma generation space; A means for generating a magnetic field, which is parallel and has a strength to generate electron cyclotron resonance in the plasma generation space, an exhaust means for adjusting a reaction pressure in the plasma generation space, and in the plasma generation space, Means for arranging the substrate at a position where the intensity of the magnetic field decreases toward the substrate in the direction of propagation of the microwave, and at the isomagnetic field surface and in the maximum region of the standing wave, Plasma CVD apparatus. 4. 4. The plasma CVD apparatus according to claim 3 , wherein the equal magnetic field surface is approximately 875 Gauss.