JPH11273895A - Plasma generating device using microwave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To design a plasma generating device by using a specific expression, for working/processing an object by means of microwave plasma, for example, a plasma generating device for coating an object by bringing diamond to chemical vapor phase epitaxy on a surface of the object, or sputtering and etching the object, or sintering the object. SOLUTION: In a plasma generating device for heating supplied gas (H2 CH4 ) by plasma 35 and bringing diamond to chemical vapor phase epitaxy on an object 28 by means of plasmatic gas, when the thickness growth speed of the diamond growing on the object 28 and a distance from a middle part of the plasma 25 to a surface of the object 28 are expressed by H(r) and r, respectively, the thickness growth speed H(r) of the diamond or the distance r of the object 28 is determined from calculated values of an expression: H(r)=K.(1/r<2> ), where, K is a proportionality constant determined by the degree of vacuum P, a gas flow rate L, a microwave output E, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator for heating a gas supplied to a vacuum chamber by microwave plasma and processing an object with a plasma gas (gas subjected to plasma). The present invention relates to a plasma generating apparatus for performing a coating process on an object, such as chemical vapor deposition of diamond on an object surface, or a sputtering, etching, or sintering process on an object.

[0002]

2. Description of the Related Art FIG. 6 is a schematic configuration diagram of a cavity resonance type plasma generating apparatus showing a first conventional example in which diamond is chemically vapor-deposited on an object surface and a coating process is performed on the object. This plasma generator is configured to generate a plasma 13 in a resonance chamber (vacuum chamber) 12 by transmitting a microwave MW (frequency: 2450 MHz) through a rectangular waveguide 11.

The waveguide 11 has one end connected to the resonance chamber 12 and the other end connected to a microwave oscillator via an impedance matching device. A partition 14 made of a dielectric material such as quartz glass is provided between the waveguide 11 and the resonance chamber 12, and the resonance chamber 12 has an airtight structure.

Further, the resonance chamber 12 has a vacuum pump 15
The air is exhausted to form a vacuum chamber, and the resonance chamber 12 contains hydrogen (H ₂ ) gas and methane (CH ₄ ).
Gas supply pipe 1
Supplied from 6. The object 17 (for example, a silicon wafer or the like) on which diamond is to be grown is placed in the resonance chamber 1.
2 is held in a light emitting portion of the microwave plasma 13 generated in the inside.

[0005] Such a plasma generator includes a waveguide 1.
When the microwave MW is transmitted from 1, the plasma 13 is generated at a location in the resonance chamber 12 where the electric field strength of the microwave is increased. The generation of the plasma 13 heats an element gas such as a hydrogen gas or a methane gas, and causes the plasma-forming gas to cause diamond to grow on the surface of the object 17 by chemical vapor deposition.

FIG. 7 is a schematic diagram of a coaxial line type plasma generator showing a second conventional example in which diamond is chemically vapor-deposited on an object surface and the object is subjected to a coating process, and FIG. 8 is FIG. FIG. 4 is a cross-sectional view taken along the line AA of FIG. The plasma generator includes a coaxial line 21 composed of an outer conductor 21a and a rod-shaped inner conductor 21b passing through the inner center of the outer conductor 21a.
To transmit microwave MW (frequency: 2450 MHz). That is, this coaxial line 21
Are connected to a microwave oscillator via an impedance matching unit 22.

[0007] One end of the coaxial line 21 is connected to a vacuum chamber 23. The vacuum chamber 23 is separated from the coaxial line 21 by a partition member 24 in order to form an airtight structure. The partition member 24 is formed of a dielectric material such as quartz glass that transmits microwaves and does not absorb microwave power.

The above-mentioned inner conductor 21b of the coaxial line 21
The tip 21c of the vacuum chamber 2 passes through the partition member 24.
3 has entered. The distal end portion 21c protruding into the vacuum chamber 23 has a wavelength (λ /
4) The length is determined to be + n · (λ / 2). (N =
0, 1, 2, 3,...) The tip of the tip 21c has a sharp shape to concentrate the microwave electric field and to easily generate the plasma 25.

The above-mentioned vacuum chamber 23 is provided with a vacuum pump 2 for adjusting the degree of vacuum to about 1 Torr to several hundred Torr.
6 and a gas supply pipe 27 for supplying a diamond element gas such as hydrogen (H ₂ ) gas or methane (CH ₄ ) gas to the vacuum chamber 23.

On the other hand, in the vacuum chamber 23, an object (for example, a silicon wafer or the like) on which diamond is subjected to chemical vapor deposition.
And a heater 29 for heating the object 28 so that the object 28 is attached. The object 28 is arranged outside the light-emitting portion of the plasma 25, that is, at a position outside the light-emitting portion where diamond can be chemically vapor-grown outside the light-emitting portion of the plasma 25. Reference numeral 30 denotes a power supply line of the heater 29.

In this conventional plasma generator, when microwaves MW are transmitted through the coaxial line 21, the microwave electric field becomes strong at the tip of the tip 21c of the internal conductor 21b, and plasma 25 is generated. As a result, the element gas of diamond is heated by the plasma 25, the plasma gas is dropped onto the object 28, and diamond is grown by chemical vapor deposition.

The above-mentioned objects 17 and 28 for chemical vapor deposition of diamond are not limited to objects having a diamond nucleus such as a diamond substrate. The container is placed in a container, and the container is subjected to a pre-process for forming a diamond nucleus on the object surface by applying ultrasonic waves or other means.

[0013]

With respect to the above-mentioned plasma generating apparatus for processing an object using microwave plasma, a basic model on which the design is based does not yet exist, and therefore, the apparatus is relied on experience. We are currently designing.

For example, no one has any idea how the processing speed changes depending on the three-dimensional positional relationship between the plasma and the object. It was generally believed that all depended on the specific structure of the plasma generator.

In view of the above-mentioned circumstances, the present invention provides a plasma generation utilizing microwaves which can be designed for an apparatus with a target of a processing state such as coating, sputtering, etching and sintering of an object required as a product. It is intended to provide a device.

[0016]

According to the present invention, as a first invention, a gas supplied to a vacuum chamber is heated by microwave plasma, and an object is processed by a plasma gas. In a plasma generator using microwaves, the distance r from the center of the plasma to the object surface or the processing speed H of the object
(R) is defined by H (r) = K ・ (1 / r ² ) where K is a conditional expression of a proportionality coefficient determined by a degree of vacuum, a gas flow rate, a microwave output, and the like. We propose a plasma generator that utilizes the method.

As a second invention, H of the first invention is used.
In (r) = K · (1 / r ² ), the proportional coefficient K is a coefficient proportional to the cube root of the degree of vacuum P in the vacuum chamber. A plasma generating apparatus using microwaves is proposed. I do.

According to a third aspect, H of the first aspect is used.
(R) = K · (1 / r ² ), wherein the proportional coefficient K is a coefficient proportional to the cube root of the gas flow rate L supplied to the vacuum chamber, wherein the plasma generator using microwaves is characterized in that Suggest.

As a fourth invention, H of the first invention is used.
In (r) = K · (1 / r ² ), a proportional coefficient K is a coefficient proportional to the microwave output E, and a plasma generator using microwaves is proposed.

According to a fifth aspect of the present invention, there is provided a plasma generating apparatus using microwaves, in which a gas supplied to a vacuum chamber is heated by microwave plasma, and the object is processed by a plasma gas. r,
P, L, and E), H (r, P , L, E) = α · 3 √P · 3 √L · E · (1 / r 2) α: determined by the device structure or the like and the gas composition constant P: The present invention proposes a plasma generator using microwaves, characterized in that it is determined and configured according to a conditional expression of vacuum degree L: gas flow rate E: microwave output.

According to a sixth aspect of the present invention, in the first or fifth aspect, in addition to the object coating including the chemical vapor deposition of diamond as the object processing, sputtering, etching or sintering of the object is performed. We propose a plasma generator using microwaves, which is characterized by having a configuration.

[0022]

[Function] Conditions other than the distance r from the center of the plasma to the object surface, such as the degree of vacuum in the vacuum chamber, the gas flow rate supplied to the vacuum chamber, the microwave output, the gas components and the composition, the state of the object to be processed, etc. Assuming that the conditions are proportional coefficients K, the processing speed H (r) of the object is inversely proportional to the square of the distance r of the object. That is, when the light emitting portion of the plasma is used as a point light source, H
The equation (r) = KＫ (1 / r ² ) holds.

From this, the processing speed of the object can be known from the three-dimensional positional relationship between the plasma and the object. For example, the distance from the center of the plasma to the silicon wafer determines the thickness growth rate of diamond growing on the silicon wafer, that is, the distribution amount. As a result, according to the first aspect, when an object whose processing state is predetermined is produced, the processing speed of the object is set to H.
The distance r is calculated from the above formula as (r), and the plasma generator can be designed based on the calculated value.

Further, the above equation H (r) = KＫ (1 /
In r ² ), experiments confirmed that the proportionality coefficient K was proportional to the cube root of the degree of vacuum P in the vacuum chamber and the gas flow rate L supplied to the vacuum chamber, and was proportional to the microwave output E. As a result, according to the fifth aspect, in addition to the distance r to the object, the degree of vacuum P, the gas flow rate L, and the microwave output E can be determined according to the processing of the object.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applicable to coating an object, sputtering and etching an object, and the like.
The present invention can be embodied as a processing apparatus for sintering an object or the like. An embodiment in which diamond is subjected to chemical vapor deposition to coat the object will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a cavity resonator type plasma generator according to a first embodiment of the present invention.

The plasma generator according to the first embodiment has
A gas supply pipe 41 having a gas supply port 41a disposed at the center of the microwave plasma 13 is provided. Further, the plasma generator includes a vacuum chamber 42 connected to the resonance chamber 12.
, And air is exhausted from the vacuum chamber 42 by the vacuum pump 15.

Further, in this embodiment, an object 17 for chemical vapor deposition of diamond is attached to the heater 43 and the object 17 is arranged outside the light emitting portion of the plasma 13. The rest of the configuration is the same as that of the first conventional example shown in FIG. 6, and therefore, the same members and portions are denoted by the same reference characters and description thereof will be omitted.

The plasma generator configured as above is
Element gases such as hydrogen gas and methane gas supplied to the vacuum chamber 42 are all fed into the center of the plasma 13 by the gas supply pipe 41. As a result, all the supplied element gases enter the plasma 13, are heated by the plasma 13, and the gas subjected to the plasma action is heated by the heater 43 (for example, a silicon wafer, a diamond substrate, or the like). ) Diamond falls on the surface of 17 and diamond is grown by chemical vapor deposition.

From the above, a plasma generator having a high diamond growth rate and high diamond generation efficiency can be obtained. The gas supply pipe 41 is made of quartz glass,
It is composed of materials such as carbon and high melting point metal.

FIG. 2 is a schematic configuration diagram of a coaxial line type plasma generator according to a second embodiment of the present invention, FIG. 3 is a sectional view taken along line BB of FIG. 2, and FIG. FIG. 3 is a partially enlarged view showing a light emitting unit. The plasma generator of the second embodiment has a configuration in which a gas supply pipe 51 is provided in an inner conductor 21b of a coaxial line 21. The rest of the configuration is the same as that of the second conventional example shown in FIGS. 7 and 8, and therefore, the same members and portions are denoted by the same reference characters and description thereof will be omitted.

The gas supply pipe 51 is made of quartz glass,
It is made of a material such as carbon or a high melting point metal, and the gas supply port 51a at the tip is located at the tip of the tip 21c of the internal conductor 21b. In the plasma generator configured as described above, all element gases such as hydrogen gas and methane gas supplied to the vacuum chamber 23 are sent to the center of the plasma 25 by the gas supply pipe 51.

As a result, all the supplied element gases enter the plasma 25 and are heated by the plasma 25,
The gas subjected to the plasma action falls on the object 28 heated by the heater 29, and diamond is grown on the surface of the object (silicon wafer, diamond substrate, etc.) 28 by chemical vapor deposition. From this, the growth rate of the diamond is high, and the diamond is grown only by the gas heated by the plasma 25, so that a uniform crystal diamond is generated.

In the plasma generators of the first and second embodiments configured as described above, the thickness growth rate of diamond greatly varies depending on the position of the object (17, 28) with respect to the plasma (13, 25). When producing a diamond-thick product (for example, a silicon wafer), it is important to set the distance r between the objects (17, 28).

However, since there is no guide on how to set the distance r, there is no other way than to set the distance r by repeating the experiment or based on experience. Therefore,
In the above embodiment, the distance r is calculated from H (r) = K ＝ (1 / r ² ) (1), and the distance r is set according to the calculated value.

That is, assuming that the diamond growth rate for obtaining a predetermined diamond thickness is the processing rate H (r), the growth rate H (r) is equal to the plasma (13,2).
It has been confirmed by the inventor of the present application that the distance is determined in inverse proportion to the square of the distance r from the center of 5) to the plane of the object (17, 28). That is, Gauss's theorem applies to particles emitted from the center of the plasma. I explain Gauss's theorem by applying it to particles. Point source (center of plasma)
From the same amount of particles are continuously released per unit time.
At this time, the particles emitted from the point source uniformly fall on any part of the surface of the unit sphere having a unit radius with the point source as a center. The number of particles emitted from the point source per unit time is the same as the number of particles falling on the unit sphere surface for a unit time. Even when the radius of the sphere increases, the number of particles falling on the sphere surface per unit time is the same as the number of particles falling on the unit sphere surface per unit time. It also falls evenly on any part of the sphere surface. Even when the number of particles emitted from the point source changes with time, the above holds true in consideration of the time required for the particles to reach the sphere surface.

That is, although the plasma (13, 25) and the object (17, 28) have no interaction, the radiating particle lines diffuse in the inverse square, so that Newton's law of universal attraction F (r) = GMm · (1 / r ² ) or Coulomb's law indicating the force acting on the charge, F (r) = (Qq / 4πε
₀ ) · (1 / r ² ), and it was found that the formula of H (r) = K · (1 / r ² ) holds for the diamond thickness growth rate.

Accordingly, if the degree of vacuum P, the gas flow rate L, the microwave output E, the gas composition and composition, the state of the object, the heater temperature, the device structure, and the like are represented by the proportional coefficient K, H (r) =
By calculating the distance r from K · (1 / r ² ) and designing the device, a predetermined diamond thickness growth rate H (r) can be obtained.

The proportionality coefficient K in the above equation (1) is proportional to the cube root of the degree of vacuum P in the vacuum chambers (23, 42), and is 3 times the gas flow rate L supplied to the vacuum chambers (23, 42). It has been confirmed by experiments that it is proportional to the root and also proportional to the microwave power E. Therefore, Sadamare the device structure and the gas composition, as a proportional constant of the device structure and the gas composition alpha, proportional coefficient K of the equation ^{(1), K = α · 3 √P ·} 3 √L · E ··· ... (2)

As a result, the distance r from the center of the plasma (13, 25) to the surface of the object (17, 28), the degree of vacuum P,
Gas flow rate L, Overall the device main portions of the configuration of a microwave output E, or, if the apparatus designed by changing a part of main portions of the configuration is, H (r, P, L , E) = α · 3 √ calculated based on the formula of ^{P · 3 √L · E · (} 1 / r 2) ···· (3), by apparatus designed on the basis of the calculated value, a predetermined diamond thickness growth rate H ( r, P, L, E).

FIG. 5 is a schematic configuration diagram of a plasma generator according to a third embodiment designed in the same manner as the second embodiment. In the third embodiment, a gas supply pipe 61 in which a gas supply port 61a is disposed near the outer periphery of a light emitting portion of the plasma 25 is provided.
It has. Even with such a configuration, almost all of the supplied gas enters the plasma 25, so that substantially the same effects as those of the plasma generator of the second embodiment can be obtained.
It should be noted that the gas supply pipe 41 provided in the embodiment of FIG. 1 can also provide substantially the same effect by disposing the guy supply port 41a near the outer periphery of the light emitting portion of the plasma 13.

The preferred embodiment of the present invention has been described above. However, the present invention is not limited to a plasma generator for chemically growing diamond by chemical vapor deposition. Further, the present invention can be similarly applied to a plasma generator for sintering an object or the like. The vacuum chamber (2
The gas supplied to (3, 42) needs to be changed according to the processing of the object such as coating, sputtering, etching, and sintering.

In practicing the present invention, the object may be arranged at a distance r from the center of the plasma.
The present invention can be implemented even when an object is put in the light emitting portion of the plasma. Further, in order to increase the processing speed such as the coating process, it is preferable to directly introduce the gas into the plasma. However, if such a processing speed is not considered, the gas is simply supplied to the vacuum chamber. can do.

When the present invention is embodied as a coaxial line type plasma generator as shown in the second and third embodiments, the tip 21c of the inner conductor 21b is made of carbon or other materials such as tungsten, It is desirable to use a conductive material made of a high melting point metal material such as molybdenum and tantalum.

[0044]

As described above, according to the present invention, it is possible to design each main part of a plasma generator for processing an object using microwave plasma based on a calculated value obtained by calculation. .

As a result, the design and manufacture of the device according to the processing value of the object determined in advance as the product are simplified. In other words, a product having a predetermined processing value can be produced by the plasma generator designed based on the calculated value.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a cavity resonator type plasma generator according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a coaxial line type plasma generator according to a second embodiment.

FIG. 3 is a sectional view taken along line BB in FIG. 2;

4 is an enlarged partial view showing a plasma light emitting unit of the coaxial line type plasma generator shown in FIG. 2;

FIG. 5 is a schematic configuration diagram of a coaxial line type plasma generator according to a third embodiment.

FIG. 6 is a schematic configuration diagram of a cavity resonator type plasma generator showing a first conventional example.

FIG. 7 is a schematic configuration diagram of a coaxial line type plasma generator showing a second conventional example.

FIG. 8 is a sectional view taken along line AA in FIG. 7;

[Explanation of symbols]

 Reference Signs List 11 waveguide 12 resonance chamber 13 plasma 17 object 21 coaxial line 21a outer conductor 21b inner conductor 23 vacuum chamber 25 plasma 28 object 29 heater 42 vacuum chamber 43 heater

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/302 B

Claims (6)

[Claims] 1. A plasma generator using microwaves, in which a gas supplied to a vacuum chamber is heated by microwave plasma to process an object with a plasma gas, the distance r from the center of the plasma to the object surface, Alternatively, the object processing speed H (r) is determined according to the following conditional expression: H (r) = K · (1 / r ² ) K: proportionality coefficient determined by the degree of vacuum, gas flow rate, microwave output, and the like. A plasma generator using microwaves, characterized in that: 2. The plasma generator using microwaves according to claim 1, wherein the proportional coefficient K is a coefficient proportional to the cube root of the degree of vacuum P in the vacuum chamber. 3. The microwave generating apparatus according to claim 1, wherein the proportional coefficient K is a coefficient proportional to the cube root of the gas flow rate L supplied to the vacuum chamber. 4. The microwave generating apparatus according to claim 1, wherein said proportional coefficient K is a coefficient proportional to a microwave output E. 5. A plasma processing apparatus utilizing microwaves for heating a gas supplied to a vacuum chamber by microwave plasma and processing an object with a plasma gas to process the object at a processing speed H (r, P, L). the E), H (r, P , L, E) = α · 3 √P · 3 √L · E · (1 / r 2) α: constant determined by the device structure or the like and the gas composition P: degree of vacuum L : Gas flow rate E: A plasma generator using microwaves, which is defined and configured according to a conditional expression of microwave output. 6. A method according to claim 1, wherein the object is processed by sputtering, etching or sintering, in addition to the object coating including the chemical vapor deposition of diamond. (5) A plasma generator using the microwave according to (5).