JP2001122690A - Microwave plasma cvd device and method of forming diamond thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave plasma CVD device capable of uniformly and exactly forming a coating film having an appropriate thickness on the surface of a substrate even when the substrate has a large diameter, which is mounted on a substrate-supporting stand. SOLUTION: The microwave plasma CVD device is equipped with a circular vacuum chamber 10, a circular substrate-supporting stand 12 which is provided at the inside of the vacuum chamber 10 and supports a substrate 11, a plurality of electrodes 14 which are arranged at the upper side of the substrate-supporting stand 12 in the circumferential direction at a certain angular interval and which constitute a main part for a plasma generating means, a plurality of microwave guides 20 which are arranged, at least, along the circumferential direction of the vacuum chamber 10 at a certain angular interval and which have dielectric windows 13 at their tip parts, which windows 13 are connected to the corresponding plural electrodes 14, respectively, a gas supplying means 15 for supplying a source gas to the vacuum chamber 10 and a vacuum discharge means 16 for discharging the gas in the vacuum chamber 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma CVD apparatus capable of generating plasma by microwaves and forming a diamond film or the like on the surface of a substrate, and a diamond thin film formed on a substrate using the apparatus. It relates to a method of forming.

[0002]

2. Description of the Related Art Plasma jet CVD has become the mainstream of thin film diamond production due to the characteristic that the deposition rate of diamond is relatively high. It is necessary to form a diamond film with a large area,
Conventionally, there have been various proposals for the method.

[0003] For example, the method of the 36th Applied Physics Alliance Lecture Proceedings 1a-N-5 involves applying a bias to a sample substrate to increase the irradiation area of a plasma jet. No. 1199993 proposes a mechanism for rotating a substrate holder, and deposits and coats a diamond thin film while rotating the substrate holder. In addition, the proposal of US Pat. Is approximately the same as the wavelength dimension calculated from the frequency of the plasma jet microwave.

For reference, a method of forming a diamond thin film by a plasma jet CVD method is disclosed in US Pat. No. 5,555,647.
The description based on the method of No. 5 is as follows. FIG.
As shown in the figure, a plate-like electrode 65 is concentrically arranged in a reaction chamber 64 in which upper and lower plates 60 and 61 and an annular ring 63 are formed, and the electrode 65 is an annular dielectric barrier. 66 is supported by the lower plate 61. The central portion of the lower space of the dielectric barrier 66 communicates with the microwave waveguide 67, and the peripheral portion thereof is connected to the peripheral portion 6 in the reaction chamber 64 via the dielectric barrier 66.
Through 8, it communicates with a plasma generation space 70 provided between the electrode 65 and the top plate 69.

The reaction chamber 64 has a gas supply port 7 through which a raw material gas flows into the reaction chamber 64.
1 and a gas outlet 72 for evacuating the inside of the reaction chamber 64 and discharging excess gas.
With this configuration, a flat disk-shaped plasma 73 can be formed on the surface of the electrode 65 by sending a microwave into the reaction chamber 64 through the microwave waveguide 67 to excite the source gas.

[0006]

However, there are various problems in the conventional proposals for producing a large-area diamond thin film having a uniform thickness in the method of forming a diamond thin film by the plasma jet CVD method. First, US Pat.
In the proposal of No. 475, the current plasma frequency is already 2.
Since the frequency approaches 5 GHz, increasing the frequency further in accordance with this concept tends to decrease the diameter of the electrode substrate, and is not a solution to the present problem.

On the other hand, if the electrode substrate is made larger without changing the frequency, the plasma frequency must be reduced, which causes another problem that the diamond thin film formation speed is reduced. . Further, in the proposal of this US patent, since the microwave plasma CVD apparatus uses only a single microwave waveguide 67, the size of the electrode 65 that supports the base 74 is limited, and the disk base 74 is limited.
It is not possible to form a diamond film or the like to a uniform thickness on the surface of the substrate.

Further, in the proposal of Japanese Patent Application Laid-Open No. 4-1191993, the diameter of a diamond thin film is limited to at most about 20 mm, and if a larger diameter is to be obtained, a larger capacity apparatus is required. Come. Some commercially available devices use a 915 MHz long-wavelength microwave, and some have a power-up product of 100 kW.
Can form a diamond film at a film formation rate of 5 μm / hour or more, but the cost of these devices is extremely high, and its practical value is questionable.

[0009] Therefore, the increase in capacity leads to an increase in equipment cost, which raises the price of the diamond thin film, and further delays the practical use. In addition, making the substrate freely rotatable as proposed in Japanese Patent Application Laid-Open No. H4-119993 is likely to provide a seemingly uniform diamond, but in the case of a single electrode device, a uniform plasma can be obtained. Inability to do so results in alternate precipitation of good and bad diamonds,
There is a problem that only a nonuniform diamond film can be obtained as a whole.

Conventionally, it has been found that the following relationship exists between the conditions for forming a diamond film by the microwave plasma method and the characteristics of the formed diamond film. In other words, in order to obtain a high-quality large-area diamond film at high speed, the use of high-energy plasma is indispensable. However, as the distance from the center of the high-energy plasma increases, the diamond characteristics such as film thickness and film quality increase. Variations increase, while if the variation in diamond characteristics is to be kept small, the deposition rate must be sacrificed because the plasma temperature must be lowered. An object of the present invention is to solve the above trade-off condition and to obtain a large-area high-quality diamond film at a low cost. The present invention is applicable to a case where a substrate placed on a substrate support is a large circle. However, the microwave plasma C can uniformly and surely form a film having an appropriate thickness on the surface of the substrate.
An object is to provide a VD device.

[0011]

In order to achieve the above object, a microwave plasma CVD apparatus according to claim 1 is provided.
A circular vacuum container, a circular substrate support pedestal disposed in the vacuum container and supporting the substrate, and a plasma generating means disposed at a predetermined angular interval in the circumferential direction above the substrate support pedestal. And a plurality of electrodes forming a main part of the vacuum vessel are arranged at a constant angular interval along at least the circumferential side of the vacuum vessel, and a dielectric window provided at the tip thereof is connected to the corresponding plurality of electrodes, respectively. A plurality of microwave waveguides, gas supply means for supplying a raw material gas to the vacuum vessel, and vacuum exhaust means for exhausting the gas in the vacuum vessel.

The microwave plasma CVD apparatus according to the present invention is also characterized in that the microwave plasma CVD apparatus has the following configuration. A plurality of telescopic microwave waveguides are arranged along the circumference of the vacuum vessel and are concentrated near the center circle. Since the base support is vertically movable up and down, the distance between the base and the electrode can be freely adjusted. The base support is rotatable both clockwise and counterclockwise, so that the number of rotations can be freely changed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the accompanying drawings. First, Figure 1
Referring to FIG. 2, a microwave plasma CVD apparatus according to one embodiment of the present invention will be described. As shown in FIG. 1, a circular substrate support 12 for supporting a substrate 11 is provided inside a circular vacuum vessel 10. Above the substrate support 12, a plurality of electrodes 14 forming a main part of the plasma generating means are arranged at intervals in a circular direction.

As shown in FIG. 2, a plurality of telescopic microwave waveguides 20 are arranged at a predetermined angle from the circumferential direction of the vacuum vessel 10 toward the center thereof.
Are converged at the center of the circle. FIG. 2A shows a case where two microwave waveguides are installed in the relative direction, and FIG. 2B shows a case where four microwave waveguides are arranged at an angular interval of 90 degrees.
In this example, the angular intervals of the microwave waveguides are set equal, but they are not necessarily equal.

The reason why the microwave waveguide is arranged in this manner is that the plasma is generated repeatedly by the arrangement of the plurality of electrodes, and a wide area of the plasma can be secured. The state of plasma generation when shifted slightly is shown schematically. That is, FIG.
3c are the two directions corresponding to FIG.
Corresponds to the case of four directions corresponding to FIG. 2B, and the overlapping range of the generated plasma can be freely adjusted by adjusting the electrode position.

Hereinafter, for convenience of explanation, the case of two microwave waveguides, that is, the case of FIG. 2A will be described.
Returning to FIG. 1, a dielectric window 13 made of a dielectric such as quartz glass provided at the front end of the microwave waveguide 20 is connected to a corresponding plurality of electrodes 14. Vacuum container 10
A gas inlet 15 for supplying a raw material gas (for example, a mixed gas of hydrogen and methane) into the vacuum vessel 10 and a gas flow for evacuating the inside of the vacuum vessel 10 and discharging excess gas An outlet 16 is provided.

The space 17 formed inside the dielectric window 13 is connected to each microwave waveguide 20. On the other hand, the upstream end of each microwave waveguide 20 is connected to a magnetron 25 that generates microwaves via an incident wave power motor 21, a tuner 22, a reflected wave power motor 23, and an isolator 24. Since the microwave waveguide 20 has a bellows type expansion joint structure, the electrode position on the substrate can be easily adjusted.

The configuration of each part of the microwave plasma CVD apparatus will be described in more detail as follows. The circular vacuum vessel 10 has a structure in which the upper part, the lower part, and the periphery thereof can be water-cooled, and a cylindrical vacuum space 29 is formed therein. Circular vacuum space 29
A circular base support base 12 is provided below the lower wall 27a,
It is arranged to be able to move up and down through a through hole 30 provided in 27b. The base support 12 is linked to an elevating device 31 including a hydraulic cylinder and the like positioned below the base support 12, and
The base support 12 and the base 11 placed and supported on the top surface of the base support 12 by driving the lifting / lowering device 31.
Can be raised and lowered steplessly. The base support 12 also has a water-cooled structure to receive high heat.
A base mounting plate 32 for mounting and supporting the base 11 is fixed.

The base of the elevating device 31 is fixedly mounted on a turntable 33. The turntable 33 is mounted on a guide platen or the like so as to be rotatable by a rotation mechanism. In the method, for example, a linear ball shaft fixed to the bottom of the turntable is rotated by a rotation motor so that a constant rotation can be obtained, but the rotation method can be based on other methods known in the art. it can. On the other hand, two hollow disk-shaped electrodes 14 are arranged in the upper central portion of the vacuum space 29 of the vacuum vessel 10 so as to face the base support 12, and each electrode 14 has an end face downward. An electrode small-diameter portion 34 protruding toward the electrode portion and an electrode large-diameter portion 35 having an annular end surface located above the end surface of the small-diameter portion 34 are formed.

Each electrode 14 also has a cooling structure to receive high heat. That is, as shown in a partially enlarged view around the electrode in FIG. 4, a cooling water inflow space 36 is formed inside the large diameter portion 35 of the electrode 14, and a cooling water supply pipe 37 is provided in the cooling water inflow space 36. A cooling water pipe 39 having a double pipe structure of a cooling water recirculation pipe 38 and a cooling water recirculation pipe 38 has an open end. Cooling water piping 3
9 is led out through a cooling water through hole 40 provided inside the upper wall 26 of the vacuum vessel 10, and is then discharged outside across the end of the downstream horizontal pipe 18 of each microwave waveguide 20. ing.

With respect to the microwave passage, an annular communication hole 41 is formed between the inner peripheral surface of the cooling water through hole 40 and the outer peripheral surface of the cooling water pipe 39, and the lower end of the annular communication hole 41 is formed by a dielectric window. 13 and communicates with a space 17 of a dielectric window. On the other hand, the upper end of the annular communication hole 41 is connected to the inner peripheral surface of the downstream horizontal pipe 19 of the microwave waveguide 20 and the cooling water pipe 39.
Microwave vertical waveguide channel 4 formed between outer peripheral surface of
2 through the downstream horizontal tube 19 of the microwave waveguide 20.
Is connected to the horizontal waveguide channel 43 at the end portion.

A block 44 is provided around the cooling water pipe 39 at the end of the waveguide horizontal portion 19 of the microwave waveguide 20 for appropriately bending the microwave flowing in the horizontal direction in the orthogonal direction. ing. That is, in each microwave waveguide 20, a thick disk-shaped block 44 is attached to the upper surface of the waveguide horizontal portion 19 so as to concentrically surround the cooling water pipe 39. Is formed in a tapered shape whose diameter gradually decreases downward. The material of the block 44 is not particularly limited as long as it has low microwave absorption, but a metal such as aluminum or an alloy containing aluminum is preferable.

Returning to FIG. 1, the base of the first plasma regulating plate 45 is provided on the upper side of the vacuum space 29 inside the vacuum vessel 10 on both sides of the microwave waveguide dielectric window 13 and the electrode 14 with a water-cooled upper portion. The lower surface of the wall 26 protrudes over substantially the entire length. Note that the first plasma regulating plate 45 is not shown in FIG. 1 due to the layout of the drawing, and is shown in FIG. 3 as being partially disposed. The material of the first plasma regulating plate 45 is also preferably aluminum or an aluminum alloy, similarly to the block 44.

Further, a second plasma regulating plate 46 is provided adjacent to the periphery of the substrate support table 12. The second plasma regulating plate 46 is, as shown in FIG.
2 may be disposed adjacent to the periphery of the substrate support table 12 or may be disposed close to the periphery of the substrate support table 12, and may be disposed separately from the substrate support table 12 below the vacuum space 29. You may. The height of the second plasma regulating plate 46 is not limited to the shape as shown in FIG. 1, and the height of the electrode 14 is set so that the plasma 47 having the maximum thickness is formed on the electrode 14. In this case, it is more preferable that the upper end surface of the second plasma regulating plate 46 extends upward to substantially the same height as the surface of the base 11.

Next, a method for forming a coating made of a hard substance on the surface of the substrate 11 using the microwave plasma CVD apparatus having the above-described configuration will be described. By applying a smoothed DC voltage to each magnetron 25 after full-wave rectification, the microwaves continuously oscillated at a constant output from each magnetron 25 are separated by the isolator 2.
4. Via reflected wave power motor 23, tuner 22, incident wave power motor 21, microwave waveguide 20,
The substrate 11 is guided into the vacuum vessel 10 through each of the dielectric windows 13 and irradiates the base 11 supported on the circular base support 12. Then, a film made of a hard substance such as diamond can be formed on the surface of the substrate 11 by decomposition of the source gas.

At this time, the substrate support 12 is formed in a circular shape, and the dielectric window 13 and the electrode 14 are arranged on the substrate support 12 so as to converge at a constant angle in the diameter direction. Therefore, the plurality of plasmas 4 having a sufficient length in the diametric direction on the base support 12 are provided.
7 can be generated, and even if the substrate 11 has a sufficient length in the diameter direction, a coating made of a hard substance can be formed on the surface of the substrate 11 with a constant thickness. When a small-diameter substrate is used, the position of the stretchable waveguide is shifted, and only one arbitrary waveguide is used, and the dielectric window 13 and the electrode 14 of the waveguide are used. Immediately below, a small-diameter substrate 11 is provided, and a coating made of a hard substance can be formed on the surface of the substrate.

In the case of this embodiment, the vacuum vessel 10
Since a plurality of microwave waveguides 20 are annularly arranged at predetermined angular intervals on both outer sides of the
Even when the structure is large, the distance between the stacked body composed of the dielectric window 13 and the electrode 14 can be reduced, and the plasma 47 having a uniform thickness can be generated on the base support 12. Further, in the case of the present embodiment, since the base support 12 is configured to be rotatable, the plasma 47 having a uniform flat thickness can be generated on the base support 12 also from this surface.

In addition, in the present embodiment, the base support 1
2 can be raised and lowered steplessly by driving the lifting / lowering device 31, so that a plasma 47 having a desired shape can be formed in the plasma formation space between the surface of the substrate 11 and the electrode 14. Regardless of the thickness or shape of the substrate 11, a coating having a uniform thickness can be formed on the surface of the substrate 11. In particular, by flattening the plasma 47 as much as possible, it is possible to form a coating having a uniform thickness even on the substrate 11 having a large diameter and a large area.

[0029]

Example 1 Diameter 1 wrapped with diamond abrasive
A silicon wafer having a thickness of 26.5 mm and a thickness of 0.625 mm was prepared as a substrate. Using a magnetron for microwave generation with an output of 6 kW per unit, a diamond film forming apparatus having an electrode arrangement as shown in FIGS.
A diamond film was manufactured as follows. The properties of the obtained diamond are shown in Table 1 in comparison.

First, the inside of the vacuum vessel 10 is evacuated to 0.6 Pa, and then hydrogen gas is supplied at a rate of 15 l / min.
It was introduced inside, and a DC voltage was applied to the magnetron 25 to generate plasma. When the plasma is flattened and stable, methane gas is supplied from the gas inlet at 0.147 MPa.
At a pressure of 0.10 ± 0.05 l / min,
Diamond was deposited on the substrate while maintaining the pressure inside the container 10 at 0.0127 MPa. In this case, the substrate was rotated at about 100 rpm as needed. In Table 1, “two directions” means the electrode arrangement shown in FIG. 2A, and “four directions” means the electrode arrangement shown in FIG. 2B. The “two-way rotation” means that the substrate is rotated at 100 rpm with the electrode arrangement shown in FIG. 2A.

[0031]

[Table 1]

The properties of diamond were measured as follows. (1) The film formation area and thickness were based on actual measurements. (2) The film formation rate was determined by measuring the diamond weight and calculating from the film formation area and density. (3) The film quality was evaluated by measuring the baseline absorption in Raman spectrum, the peak half width at 1333 cm ^{- 1} , and the thermal conductivity, and comprehensively evaluating these values. The Raman spectrum was measured by a Raman spectrometer SYSTEM-3000 manufactured by JEOL Data Systems Co., Ltd., and the thermal conductivity was measured by an optical AC method thermal constant meter PIT-R2 manufactured by Vacuum Riko Co., Ltd.
Type used. (4) The estimated diamond price is a comparison value comprehensively calculated from the apparatus price, raw materials, operating costs (time required to obtain a constant thickness diamond), and the like.

[0033]

As described above, according to the present invention,
A circular substrate support for supporting the substrate is provided in a circular vacuum vessel, and a plurality of microwave waveguides and a plurality of electrodes forming a main part of the plasma generating means are circumferentially spaced above the substrate support. The microwave plasma CVD apparatus was constructed by connecting the dielectric windows provided at the front end thereof to the corresponding plurality of electrodes, respectively, so that a sufficient length was provided in the diameter direction on the base support. Can be generated, and even if the substrate has a sufficient length in the longitudinal direction, a coating made of a hard substance can be reliably formed on the surface of the substrate. In addition, by changing the number of the plurality of laminated bodies composed of the dielectric window and the electrode, even if the substrate has a small diameter, a coating made of a hard substance can be reliably formed on the surface thereof.

Further, by arranging a plurality of microwave waveguides circumferentially on both outer sides of the vacuum vessel with a space therebetween, even if the structure of the magnetron is large, the laminated body including the dielectric window and the electrodes can be formed. The distance between the substrates can be reduced, and plasma having a uniform thickness can be generated on the base support. Further, since the base support is configured to be rotatable, a plasma having a uniform thickness can be generated on the base support also from this surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an overall configuration of a microwave plasma CVD apparatus according to one embodiment of the present invention.

FIG. 2 is a plan view showing an arrangement state of a plasma waveguide.

FIG. 3 is a schematic diagram of a state of generated plasma.

FIG. 4 is an enlarged view of a portion around an electrode shown in FIG.

FIG. 5 is a configuration explanatory view of a conventional microwave plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Vacuum container 11 ... Substrate 12 ... Substrate support stand 13 ... Dielectric window 14 ... Electrode 15 ... Gas inlet 16 ... Gas outlet 17 ... Dielectric Window space 19 ・ ・ ・ Horizontal part of waveguide 20 ・ ・ ・ Microwave waveguide 21 ・ ・ ・ Power motor of incident wave 22 ・ ・ ・ Tuner 23 ・ ・ ・ Power motor of reflected wave 24 ・ ・ ・ Isolator 25 ・ ・ ・Magnetron 26 ・ ・ ・ Water-cooled upper wall 27a ・ ・ ・ Security seal plate 27b ・ ・ ・ Security seal plate 30 ・ ・ ・ Through hole 31 ・ ・ ・ Elevating device 32 ・ ・ ・ Base mounting plate 33 ・ ・ ・ Rotating table 34 ・..Electrode small diameter portion 35 ... Electrode large diameter portion 36 ... Cooling water inflow space 37 ... Cooling water supply pipe 38 ... Cooling water circulation pipe 39 ... Cooling water pipe 40 ... Cooling water penetration Hole 41: Annular communication hole 42: Microphone Wave vertical waveguide channel 43 ... Microwave horizontal waveguide channel 44 ... Block 45 ... First plasma regulation plate 46 ... Second plasma regulation plate 47 ... Plasma 60 ... Top Plate 61: Lower plate 63: Annular ring 64: Reaction chamber 65: Electrode 66: Annular dielectric barrier 67: Microwave waveguide 68: Peripheral edge of the reaction chamber 69 ··· Top plate 70 ··· Plasma generation space 71 ··· Gas supply port 72 ··· Gas outlet 73 · · Plasma 74 ··· Base mounting plate 75 ··· Intermediate support plate 80 ··· Exhaust pump

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshio Uchiyama 1296-1, Toyoi, Higashitoyoi, Kudamatsu City, Yamaguchi Prefecture Inside the Technical Research Center of Toyo Kohan Co., Ltd. (72) Inventor Masaru Inoue 1, 1296, Higashitoyoi, Kudamatsu City, Yamaguchi Prefecture 4G077 AA03 AB03 BA03 DB07 DB19 ED06 EG25 EG29 TA04 TA11

Claims (6)

[Claims] 1. A circular vacuum container, a circular substrate support base provided in the vacuum container and supporting a substrate, and a predetermined angular interval in a circumferential direction above the substrate support base. A plurality of electrodes, which are arranged and form a main part of the plasma generating means, correspond to at least a constant angular interval along at least the circumference of the vacuum vessel, and correspond to a dielectric window provided at the tip thereof. A plurality of telescopic microwave waveguides respectively connected to the plurality of electrodes, gas supply means for supplying a raw material gas to the vacuum vessel, and vacuum exhaust means for exhausting gas in the vacuum vessel are provided. Microwave plasma CVD equipment. 2. The microwave plasma according to claim 1, wherein the plurality of microwave waveguides are arranged at a constant angular interval on a circumference of the vacuum vessel and converge at a center of the circle. CVD equipment. 3. The method according to claim 1, wherein the two microwave waveguides are arranged at an angular interval of 150 to 180 ° on the circumference of the vacuum vessel, and are converged at the center of the circle. Microwave plasma CVD equipment. 4. The apparatus according to claim 1, wherein four microwave waveguides are arranged at an angular interval of 1 to 120 ° on the circumference of the vacuum vessel, and are converged at the center of the circle. Microwave plasma CVD equipment. 5. The method according to claim 5, wherein the base support is moved in the circumferential direction by 10-1.
3. The microwave plasma CVD apparatus according to claim 1, wherein the apparatus is rotatable at a speed of 000 rpm. 6. A diamond thin film having a thickness (μm) / diameter (mm) ratio of 0.10 or less per hour on a circular silicon substrate by using the microwave plasma CVD apparatus according to claim 1 or 2. How to form.