JPH0524986A - Vapor phase synthesis method for diamond - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a diamond thin film coated tool capable of increasing adhesivity between a substrate and a diamond thin film by a microwave plasma CVD method. CONSTITUTION:The circumference of a substrate 2 is deposited with a conductive thin sheet-shaped frame 3 in such a manner that the direction of the frame 3 is made perpendicular to the electric field direction of a microwave as well as the length in the electric filed direction of the microwave of the frame 3 is increased more than that of the substrate 2, by which the surface of the substrate is coated with a diamond thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the adhesion between a substrate and a diamond thin film in the field of tools such as a cutting tip, a drill or a milling cutter coated with a diamond thin film by a vapor phase synthesis method.

[0002]

2. Description of the Related Art Today, diamond can be easily synthesized from a vapor phase at a low pressure, and application development utilizing the characteristics of the vapor phase synthesis method is actively pursued. The biggest problem in putting the diamond thin film by the vapor phase synthesis method into practical use in the field of mechanical tools is that the adhesion between the substrate and the diamond thin film is low and it cannot be put to practical use. The main reason for this low adhesion is the stress caused by the difference in the coefficient of thermal expansion between the substrate and diamond, that is, the residual temperature that occurs when the substrate is coated with a diamond thin film and when the diamond thin film is coated and then cooled. Due to stress. In the vapor phase synthesis method of diamond, many methods have been proposed to improve the adhesion between the substrate and the diamond thin film. For example, there are the following methods. 1) Japanese Unexamined Patent Publication No. 2-188494 2) Japanese Unexamined Patent Publication No. 2-188495 1) is a method in which the surface of a substrate on which a thin film is formed and the surface of a holding member are flush with each other, so that plasma causes The present invention relates to a method for forming a diamond thin film having a uniform film thickness while preventing the diamond film from being locally concentrated on the formation surface. The method 2) relates to a method of forming a diamond thin film on a substrate having a non-planar special shape by allowing an auxiliary member to exist in the vicinity of the convex portion of the substrate having a convex portion.

When the diamond thin film is coated on the surface of the substrate by the microwave plasma CVD method, discharge is likely to occur from the edge portion of the substrate, and the temperature at the discharge site becomes 1000 ° C. or higher. According to the method 1), since the thin film formation surface of the substrate and the surface of the holding member are on the same surface, it is not possible to completely suppress the discharge from the edge portion of the substrate and only to endure practical use at the discharge site. That is, the adhesion cannot be obtained, that is, as shown in Example 1, peeling occurs at a rate of 5% when the diamond thin film is coated and then cooled and taken out. Further, considering the volume and material of the holding member, it is expected that the heat capacity of the holding member is about the same as that of the base body, and on the side surface of the base body, the excited species generated by exciting the source gas by the plasma is the holding member. Therefore, there is a problem that graphite is likely to be formed because of rapid cooling. Further, also by the method of 2), discharge is likely to occur between the convex portion of the thin film forming member having the convex portion and the auxiliary member, and it is not possible to obtain the practical adhesion strength as in the method of 1) above. There is a problem that if the CVD condition is set so that diamond is easily formed on the convex portion, graphite is easily formed on the side surface.

[0004]

Although diamond has been obtained from the gas phase at a low pressure and a wide range of applications are being developed at present, the problem of adhesion between the substrate and the diamond thin film and any shape are desired. The technique for coating the surface of the substrate having the heat treatment has not been solved yet.

The object of the present invention is to solve the above-mentioned problems, and microwave plasma CVD is applied to a flat substrate surface such as a cutting tip and a rod substrate surface such as a drill. A vapor phase synthesis method of diamond capable of coating a diamond thin film by a method and obtaining an adhesion force with a diamond thin film that can be practically used as a tool.

[0006]

In the vapor phase synthesis method of diamond by the TE plasma microwave plasma CVD method, it is possible to suppress the occurrence of microwave discharge directly from the surface of the substrate, and to place the microwave plasma away from the substrate. If the raw material gas is excited in the plasma and the excited species are guided to the surface of the substrate so that the diamond thin film can be coated under the optimum CVD conditions, the adhesion between the diamond thin film and the substrate will be improved. We were able to anticipate it and realize the technology, which led to the present invention.

That is, the microwave plasma C in TE mode
In the vapor phase synthesis method of diamond by the VD method, a conductive thin plate-shaped frame is provided around the base, and the direction of the frame surface is perpendicular to the electric field direction of the microwave, and the microwave of the frame is By arranging so that the length in the direction of the electric field is longer than that of the substrate, the adhesion between the substrate and the diamond thin film could be improved. In particular, by using a wire mesh as the thin plate-shaped frame, it was possible to coat the side surface of the substrate with the diamond thin film having a low graphite content.

As the material of the conductive thin plate frame, a material having a high heat resistance and easily emitting thermoelectrons when heated by microwave discharge without promoting the formation of graphite, specifically, molybdenum, tantalum or Tungsten or the like is preferable. The thin plate-shaped frame has a wall thickness of 0.01 to 3 mm, particularly 0.
It is preferably in the range of 1 to 1 mm. If the frame is thin, it is melted by microwave discharge, and conversely, if it is thick, the heat capacity of the thin plate-like frame is large, and the excited species generated when the source gas is excited by the plasma are cooled by the frame, so that the graphite is Are easily formed. The length of the thin plate-shaped frame in the microwave electric field direction is 0.1 to 0.1 mm from the base.
The length is preferably 20 mm, particularly 1 to 10 mm. If the length is short, the discharge from the edge portion of the substrate cannot be completely suppressed, and conversely, if the length is long, the distance between the plasma and the substrate becomes long, so that graphite is likely to be formed on the surface of the substrate.
The distance between the thin plate-shaped frame and the substrate is preferably 0.1 to 10 mm, particularly preferably 1 to 5 mm. If the interval is short, the substrate is greatly affected by the heat of the plasma, so that the adhesion is not improved. On the contrary, if the interval is long, the distance between the plasma and the substrate becomes large, so that graphite is easily formed. The structure of the thin plate frame is particularly preferably a mesh. The reason for this is that when the source gas passes through the mesh of the mesh-shaped frame, the mesh-shaped frame is red-heated by the microwave discharge and excited by the emitted thermoelectrons,
This is because, like the upper surface, the side surface of the substrate can also satisfy optimum CVD conditions for forming diamond.
When using a mesh-shaped frame as a thin plate-shaped frame, suppress the discharge from the edge of the substrate by installing so that the direction of the vertical lines that make up the mesh is parallel to the electric field direction of the microwave. can do. The mesh-shaped frame has a wire diameter of 0.01-
It is 1 mm and the opening is 0.01 to 2 mm. If the wire diameter is small, the wire mesh will be melted by the temperature of the plasma, and if the wire diameter is thick, unevenness will occur in the formation of the diamond thin film on the substrate surface due to the effect of the wire.
If the mesh size is small, graphite is likely to be formed on the side surface of the substrate, and conversely, if the mesh size is large, discharge easily occurs from the edge portion of the substrate.

In the present invention, as the substrate, a cemented carbide,
A molded product made of cermet, ceramics or the like can be used.

Any known gas can be used as the raw material gas for diamond.

[0011]

A conductive thin plate-shaped frame is provided around the base, and the direction of the plane of the frame is perpendicular to the electric field direction of the microwave, and the length of the frame in the microwave electric field direction is longer than that of the base. The position of the plasma can be controlled by preferentially causing the microwave discharge from the tip of the frame that is longer than the substrate in the electric field direction of the microwave. In this way, by suppressing the occurrence of microwave discharge directly from the substrate, it is possible to relieve the residual stress due to the difference in the coefficient of thermal expansion between the substrate and diamond. Furthermore, by reducing the thickness of the conductive thin plate frame to keep the heat capacity small, the frame is red-heated by the microwave discharge and acts as a thermoelectron emitting material, emitting thermoelectrons and emitting raw materials near the frame. Since the gas is excited, the diamond thin film can be coated also on the side surface of the substrate.

[0012]

EXAMPLES The present invention will be described below with reference to examples. Example 1 FIG. 1 is a schematic configuration sectional view of a reaction apparatus used in an example of the present invention. In FIG. 1, a cemented carbide drill (JISK10) with an outer diameter of 1 mm is used as a substrate inside the reactor 1.
2 is installed, and the wire diameter is 0.02 mm and the opening is 0.
A 5 mm tungsten wire mesh 3 was installed in a cylindrical shape. At this time, the distance between the drill and the wire mesh was 1.2 mm, and the length of the wire mesh in the microwave electric field direction was 5 mm longer than that of the substrate.

Then, by using a vacuum device, the reactor was 5 × 10 5.
After exhausting to ^-6 Torr, an alternating current is applied to the substrate holder-4 to raise the temperature to 600 ° C., hydrogen is supplied at a rate of 200 SCCM (standard state conversion is cubic centimeter per minute), and methane is supplied at a rate of 2 SCCM. The pressure was adjusted to 50 Torr.

Subsequently, a TE mode microwave of 600 W was introduced into the reactor from a microwave oscillator through an isolator, a power monitor, a three-stub tuner, a waveguide 5 and a quartz glass 6. .

Then, electric discharge was generated from the tip of the wire mesh, plasma was generated so as to wrap around the tip of the wire mesh, and the wire mesh was red-heated by the microwave discharge. At this time, discharge from the drill was not recognized. Under the above conditions, the drill surface was coated with a diamond thin film for 8 hours.

As a result, a 4 μm diamond thin film was coated on the surface of the drill over a length of 10 mm from the tip of the drill.

Using this drill, a glass epoxy printed circuit board (equivalent to G10) having a thickness of 1.5 mm was rotated at a rotation speed of 1
When drilling was performed under the conditions of 10,000 rpm and a feed rate of 0.05 mm / revolution, no peeling of the diamond thin film was observed.

Comparative Example 1 FIG. 2 is a schematic sectional view of a reactor used in a comparative example of the present invention. In FIG. 2, a drill 2 having the same material and shape as used in Example 1 as a substrate inside a reactor 1, and a tungsten wire 7 having a wire diameter of 1 mm as an auxiliary member has a distance of 1 mm from the tip of the drill. It was arranged as follows. Other conditions were the same as in Example 1, and an attempt was made to coat the surface of the substrate with a diamond thin film.

Then, discharge was generated from the tip of the drill. After 2 hours, the drill was bent due to the heat generated by the discharge. When the drill was taken out after 8 hours, the formation of diamond was not recognized because the temperature was too high.

Example 2 In Example 1, instead of a drill as a substrate, a cemented carbide cutting slow-away tip (JIS K10, TN) was used.
GG160404R) is installed and the wall thickness is around 0.
Substrate under the same conditions as in Example 1 except that a 5 mm thin plate made of molybdenum was installed such that the length of the microwave in the electric field direction was 1.1 mm longer than the substrate and the distance to the substrate was 2.0 mm. The surface was coated with a diamond film for 20 hours.

Then, discharge was generated along the molybdenum frame, plasma was generated so as to wrap the substrate, and the frame was red-heated by the microwave discharge. At this time, no direct discharge from the substrate was observed.

As a result, the upper surface of the substrate and 1 mm from the upper surface
And the side surface was coated with a diamond thin film having a thickness of 10 μm.

Using this cutting tip, silicon 12w
Cutting speed of round bar of aluminum alloy containing t% is 300m
/ Min, feed 0.15 mm, notch 0.5 mm
When the cutting was evaluated by a CNC lathe for 10 minutes under the above cutting conditions, no peeling of the diamond thin film was observed.

Comparative Example 2 In Example 2, the length in the microwave electric field direction was exactly the same as the length of the throw-away tip around the throw-away tip for cemented carbide cutting made of the same material and shape. A diamond thin film was coated on the surface of the substrate under the same conditions as in Example 2 except that an auxiliary member having a width of 5 mm and a material equivalent to JIS K10 was installed so that the distance from the throw-away tip was 1 mm.

Then, discharge was generated at two points on the edge of the substrate, the diamond thin film was coated and then cooled to room temperature to take out the throw-away chip, and the diamond thin film was peeled off at the portion where discharge was generated.

According to the present invention, by disposing a conductive thin plate-shaped frame around the base, it is possible to suppress direct discharge from the base, and the thin plate-shaped frame is provided with microwaves. Since red heat is generated by the discharge and thermoelectrons are emitted, it is possible to manufacture a tool in which the surface of the substrate is coated with a diamond thin film having high adhesion.

[0026]

[Brief description of drawings]

FIG. 1 is a schematic structural cross-sectional view of a reaction apparatus used in an example of the present invention.

FIG. 2 is a schematic structural cross-sectional view of a reaction device used in a comparative example of the present invention.

[Explanation of symbols]

1 reactor 2 Cemented carbide drill 3 Tungsten wire mesh 4 Base holder 5 Waveguide 6 Quartz glass 7 plasma 8 Tungsten wire

Claims (2)

[Claims] 1. TE mode microwave plasma CVD
When the diamond thin film is coated on the surface of the substrate by the method, a conductive thin plate frame is provided around the substrate so that the direction of the surface of the frame is perpendicular to the electric field direction of the microwave. A method for vapor phase synthesis of diamond characterized in that the frame is arranged such that the length of the frame in the direction of the electric field of microwaves is longer than that of the substrate, and the surface of the substrate is coated with a diamond thin film. 2. The thickness of the conductive thin plate frame is 0.01 to.
The vapor phase synthesis method for diamond according to claim 1, wherein the length is 3 mm.