JPH0874056A - Diamond coated substrate and its production - Google Patents

Abstract

PURPOSE: To form a thick diamond coating film on a substrate by a vapor phase synthesis method without causing warpage and to produce a diamond coated substrate excellent in adhesion, subjected to easy polishing for flattening the surface of the coating film and less liable to the cracking of t.he coating film at the time of brazing to a tool. CONSTITUTION: When a diamond coating film is formed on a substrate by a vapor phase synthesis method, compressive stress and tensile stress are selectively and alternately produced in the coating film by varying the temp. of the substrate and the stresses are compensated with each other. The objective thick diamond coating film is formed on the substrate without causing warpage to the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond coating used for tools such as cutting tips, drills and end mills, and a method for producing the same. More specifically, the present invention relates to a diamond-coated substrate having a flat shape that does not warp by canceling internal stress generated in the diamond film during film formation, or a diamond film separated from the substrate, and a method for producing the same.

[0002]

2. Description of the Related Art With the development of a vapor phase synthesis method for diamond, the development of a diamond coated tool in which a tool base such as a cutting tip, a drill and an end mill is coated with diamond by vapor phase synthesis has been vigorously pursued. When a diamond film is formed directly on the tool substrate from the vapor phase, depending on the method, the stress caused by the difference in the coefficient of thermal expansion between the substrate material and diamond, that is, when the substrate is coated with the diamond film and after coating Due to the residual stress caused by the temperature difference during cooling, the diamond film peels off from the substrate, making it difficult to put into practical use. On the other hand, a method in which a specific substrate is coated with diamond in advance by a vapor phase synthesis method, and then the obtained diamond-coated substrate is brazed to a tool so that the substrate contacts the tool, or the diamond surface contacts the tool After brazing to the tool as described above, a method of polishing and removing the substrate, or a method of peeling the diamond film from the diamond-coated substrate and brazing only the diamond film to the tool are also used. In these methods, the residual stress increases as the thickness of the diamond coating increases, and when the substrate is thin, the diamond-coated substrate warps. When the warp occurs, it is troublesome when the surface of the coating film is flatly polished, or the diamond coating film is easily cracked when brazing to a tool. When forming a diamond film on a substrate, the film is formed in multiple steps for the purpose of improving adhesion, and the deposited film has a multi-layer structure, for example, JP-A 1-167211 and JP-A 3-197677. Japanese Patent Laid-Open No. Hei 5-99278 and Japanese Patent Laid-Open No. 4-99278 disclose a method of preventing the film from warping when forming a diamond film.
No. 6195 is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 1-167211 discloses a diamond-like carbon layer having a high amorphous carbon content and a diamond-like carbon layer having a low amorphous carbon content. A diamond-like carbon film having excellent properties and a method for synthesizing the same are disclosed. An object of the present invention is to obtain a diamond-like carbon film having a smooth surface and a high light transmittance as a coating for lenses and windows and a protective film for magnetic disks. The temperature of the substrate, electromagnetic waves such as microwaves and high frequencies, etc. By periodically changing the energy, the concentration of the carbon source, and the reaction pressure, a diamond-like carbon layer containing a large amount of amorphous carbon,
A diamond-like carbon film is obtained by alternately depositing diamond-like carbon layers having a low amorphous carbon content in layers. However, the purpose of the present invention is to obtain a diamond-like carbon film having a smooth surface and a high light transmittance, and to obtain a film having excellent surface smoothness without performing surface polishing such as lapping after film formation. To
The outermost surface layer has excellent surface smoothness, but since it is necessary to form a diamond-like carbon layer having a low hardness and a high amorphous carbon content, it is used as a hard coating layer for tools, which is the object of the present invention. Wear resistance is not sufficient and is not suitable for.

Japanese Unexamined Patent Publication (Kokai) No. 3-197677 discloses a base material of cemented carbide, cermet, silicon nitride sintered body, or aluminum oxide sintered body, in which the impurity composition in the first layer is higher than that in the second layer. Disclosed is a diamond coating tool which is high and has a diamond particle diameter in the first layer smaller than the diamond particle diameter in the second layer. In the present invention, it is necessary to form the first layer film by the filament CVD method and then form the second layer film by the plasma CVD method in different steps. However, there is a problem in that the productivity is low and impurities such as dust may adhere to the surface of the film after forming the film of the first layer to cause defects in the film of the second layer.

Japanese Unexamined Patent Publication (Kokai) No. 4-99278 discloses a diamond coating layer containing a carbon component other than diamond and a diamond coating layer containing no carbon component other than diamond, each having one or more layers each having a thickness of 0.5 to 200 μm. Disclosed is a diamond-coated tool member in which a multilayer diamond coating layer is formed on a hard material. This invention, between the diamond layer and the substrate containing no carbon component other than diamond, containing a carbon component of the same component as the diamond in the form of amorphous carbon, by providing a tough diamond layer,
The purpose of this is to reduce the impact on the entire coating layer and to provide both peeling resistance and abrasion resistance. However, as the thickness of the coating increases, the stress generated in the coating increases, and the coating tends to peel off.

Japanese Unexamined Patent Publication (Kokai) No. 5-306195 discloses a radius of curvature for compensating the internal tensile stress predicted in a diamond thin film obtained by removing the film-forming surface of a substrate on which a diamond film is deposited from the substrate. Disclosed is a method for producing a CVD diamond thin film, which has a convex shape and has a thin film removed from a substrate, which releases its internal tensile stress by being warped in a direction opposite to the curvature of the substrate and becomes flat. There is. This invention predicts in advance the degree of warpage of the coating caused by the internal stress in the coating when depositing the diamond coating on the substrate, and peels the coating from the substrate to release the internal stress so that a flat coating is obtained. In addition, it is characterized in that the base material is previously made convex so as to cancel the warp of the film. However, the internal stress that occurs in the film increases depending on the diamond film forming equipment and film forming conditions, such as the higher the film forming rate, the more the diamond film forming conditions should be changed according to the degree of convexity of the substrate. It needs to be strictly controlled and is not practical.

[0007]

DISCLOSURE OF THE INVENTION The present invention forms a diamond film having a thickness of 5 to 2000 μm by a vapor phase synthesis method without causing the film to warp, and makes the film surface flat after film formation. It is an object of the present invention to provide a diamond-coated substrate which is easy to polish and has excellent adhesion, and which is hard to be broken when brazed to a tool, and a method for producing the same.

[0008]

According to the present invention, by changing the substrate temperature in the step of forming a diamond film on a substrate which is a wafer of either silicon or molybdenum by a vapor phase synthesis method, The stress state generated inside the diamond film formed on the substrate is changed, the compressive stress and the tensile stress are alternately generated inside the diamond film to cancel the internal stress generated in the diamond film, and the diamond-coated substrate is flat without warping. The method for producing a diamond film, which is characterized by a uniform shape, and the flatness of a diamond-coated substrate produced by a vapor phase synthesis method using a wafer of one of silicon and molybdenum as a substrate, with a radius of curvature of 8 m. The above is to provide a diamond-coated substrate having a diamond coating thickness of 5 to 2000 μm. In the present invention, when a diamond film is formed by using the same microwave output in the working gas of the same component and the same concentration, the internal stress generated in the film at a certain constant substrate temperature is the tensile stress. From the results, it was found that the compressive stress was reversed or the compressive stress was reversed to the tensile stress. As a result, the film is formed at a substrate temperature at which compressive stress is generated during diamond film formation, and subsequently the substrate temperature is changed to form a film at a substrate temperature at which tensile stress is generated during film formation, or the opposite of the above. A diamond film is formed by using the heating cycle of the substrate, or this heating cycle is repeated multiple times to cancel the tensile stress and compressive stress generated in the film, thereby forming a thick film without warping the film. That is, it is possible to form a diamond film of.

The present invention will be described in detail below. The substrate for forming a diamond film by the vapor phase synthesis method of the present invention includes metals such as silicon, molybdenum, tungsten, niobium, iron, copper, silver and nickel, graphite, non-metal simple substances such as boron, silicon carbide, carbon Although metal carbides such as tungsten, metal oxides such as alumina and silica, and nitrides such as boron nitride and silicon nitride can be used, those that have a small difference in expansion coefficient from the diamond deposited on the substrate are preferable and economical. From the standpoint of performance and practicality, a silicon or molybdenum wafer is suitable as a substrate for forming the diamond film of the present invention.

Next, the surface of the substrate is roughened by using emery paper or the like, and then a diamond film is formed by a vapor phase synthesis method in a working gas composed of hydrogen and hydrocarbon. As a gas phase synthesis method, a microwave plasma CVD method,
A filament CVD method, a DC plasma CVD method, an RF plasma CVD method, or the like can be applied, but in the present invention, microwave plasma CV whose film forming conditions can be easily controlled.
It is preferable to use the D method. Hydrocarbons that serve as the carbon source of the working gas include saturated hydrocarbons such as methane, ethane, propane and butane, unsaturated hydrocarbons such as ethylene, propylene and acetylene, alcohols such as methanol, butanol and isopropanol, acetone and methyl ethyl ketone. Although ketones, aromatic compounds such as benzene and toluene can be used, it is preferable to use methane in terms of economy and practicality. These hydrocarbons are mixed with hydrogen in a volume ratio of 1: 500 to 1: 5.
When the volume ratio is 1: 500 or less, the deposition rate of the diamond film becomes extremely small, and when it is 1: 5 or more, non-diamond carbon is co-deposited, which is not preferable. In some cases, it is possible to dilute the mixed gas by further mixing an inert gas such as argon. The mixed gas is 0.
It is fed into the reactor at a pressure of 1 to 200 Torr. If it is 0.1 Torr or less, diamond is not deposited and the substrate is etched, and if it is 200 Torr or more, the deposition range is narrowed and uniform deposition cannot be obtained over the entire substrate. In this working gas, a microwave output of 100 to 5000 W is applied and
A diamond film is formed on a substrate at a film formation rate of 0.1 to 15 μm. If the microwave output is 100 W or less, the deposition rate of the coating becomes extremely small, while if it is 5000 W or more, the deposition rate of the coating improves, but the stress generated in the coating also increases and the warpage of the coating becomes large. Even with the film formation method for suppressing the warp described in (1), it becomes extremely difficult to obtain a flat diamond film without warp.

Within the range of these film forming conditions described above, the conditions are fixed such that a suitable diamond film is obtained, the substrate temperature is changed in a plurality of vapor phase synthesis steps, and the diamond film is produced in each step. Compensates for compressive or tensile stress and forms a diamond film without warping. The substrate temperature depends on the material of the substrate and film forming conditions other than the substrate temperature, but 600 to 850 ° C to apply compressive stress to the film, and 880 to 1 to apply tensile stress to the film.
It shall be in the range of 100 ℃. If the substrate temperature is 600 ° C. or lower, the precipitation rate will be extremely low, and if it is 1100 ° C. or higher, graphite will be co-deposited, which is not preferable. Further, it is preferable that the ratio of the thickness of the film formed at each stage of vapor phase synthesis is within 3 times, respectively, in order to obtain a film having a curvature radius of 8 m or more and virtually no warpage. After the film is formed, the film surface is lapped and flattened, but if the radius of curvature is 8 m or less, the cutting margin for flattening the film becomes extremely large, which is disadvantageous in terms of cost and required for lapping. Since the time becomes long, the radius of curvature is preferably 8 m or more, and more preferably 20 m or more. The thickness of the film is 5 μm as the lower limit to ensure sufficient wear resistance of the tool coated with the film and to secure a polishing margin for polishing the film evenly after the film is formed. The upper limit is 2000 μm from the viewpoint of time and economy.

As a method of controlling the film forming conditions to cancel the internal stress generated in the diamond film, other than the method of changing the substrate temperature as described above, the composition ratio, concentration, and pressure of the working gas are changed. Although it can be achieved by a method or a method of changing the output of microwaves, the method of fixing the other variable factors and changing the substrate temperature as in the present invention can achieve the object most reliably and easily. can do.

[0013]

In the present invention, when the diamond film is vapor-phase synthesized, the components of the working gas, the concentration, the pressure and the microwave output are kept constant, the substrate temperature is changed in a plurality of vapor-phase synthesis steps, and the compressive stress or By selectively and alternately generating tensile stress to cancel the compressive stress and the tensile stress, a thick diamond film is formed without causing the film to warp. This method enables the diamond-coated substrate to have a flat shape without warping.

[0014]

The present invention will be described in more detail with reference to the following examples. (Example) As a base material for diamond coating, a thickness of 0.62
5mm, 25mm square silicon wafer and molybdenum wafer were selected. The surface of this wafer was roughened by polishing with ^# 240 emery paper, and then ultrasonically cleaned in acetone.
Microwave plasma CVD is applied to the pretreated wafer.
Using the method, the substrate was heated under the working pressure of 90 Torr in an atmosphere consisting of an output of 1150 W, a hydrogen flow rate of 95 SCCM (cm ³ / min) and a methane flow rate of 5 SCCM under the conditions shown in Tables 1 to 4 to form a diamond film. . The warpage state of the obtained diamond-coated wafer was evaluated by measuring the maximum deviation (warpage) of the diamond-coated wafer surface using a two-dimensional surface roughness meter and calculating the radius of curvature using the Pythagorean theorem. The results are shown in Tables 5-8
Shown in

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

[Table 6]

[0021]

[Table 7] (Note) ^* : Thin film thickness and poor wear resistance when applied to cutting chips.

[0022]

[Table 8] (Note) ^# : It takes a long time to form a film and the productivity is poor. [Radius of curvature measurement] Measuring equipment: Tokyo Seimitsu Co., Ltd. two-dimensional roughness meter Surfcom 15
00 A Measurement method: 1) Measurement surface: Base wafer surface or deposited diamond coating surface 2) Measurement method and calculation method Distance on base wafer surface or deposited diamond coating surface: Between two points separated by L (2l) Warpage (maximum deviation: h)
Is measured using the above two-dimensional roughness meter, and the radius of curvature R is calculated from the following equation using the Pythagorean theorem. That is, from (R−h) ² + l ² = R ² , R = (l ² +
h ² ) / 2h

As shown in the examples of Tables 5 and 6, the diamond-coated substrate of the present invention can be obtained in a flat shape with almost no warpage. On the other hand, as shown in Comparative Examples of Tables 7 to 8, when the diamond coating is formed of only one layer as shown in Comparative Examples 2 and 3, the coating may be warped due to internal stress generated in the coating, The film cannot withstand stress and may be destroyed immediately after film formation. Further, as shown in Comparative Example 5, even when a film is formed with a structure composed of a plurality of layers, the film warps when the thickness ratio of each layer exceeds three times. Further, when the thickness of the diamond film is thin, the wear resistance is poor when applied to a cutting tip or the like.
It takes a long time to form a film as thick as 0 μm,
Poor productivity and impractical.

[0024]

As described above, according to the present invention, it becomes possible to form a diamond-coated substrate having a large film thickness in a flat shape without warping, and polishing for flattening the diamond film surface after film formation. Easier, and moreover,
It is now possible to braze a diamond coating to a tool without cracking the coating.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23C 16/02 C30B 29/04 Q 9261-4G

Claims (6)

[Claims] 1. In the step of forming a diamond film on a substrate by a vapor phase synthesis method, a compressive stress and a tensile stress are alternately generated inside the formed diamond film to cancel the internal stress generated in the diamond film. A method for producing a diamond coating, characterized in that the diamond-coated substrate has a flat shape without warping. 2. The internal state produced in the diamond film by changing the temperature of the substrate, thereby changing the stress state produced inside the diamond film formed on the substrate and alternately producing compressive stress and tensile stress inside the diamond film. The method for producing a diamond film according to claim 1, wherein the stress is canceled. 3. The method for producing a diamond film according to claim 1, wherein the substrate is a wafer of any one of silicon and molybdenum. 4. The diamond film coated on the substrate has a thickness of 5 to 2000 μm.
Or the method for producing a diamond film according to any one of 3 above. 5. A diamond-coated substrate, wherein the flatness of the diamond-coated substrate produced by the vapor phase synthesis method is 8 m or more in radius of curvature, and the diamond coating has a thickness of 5 to 2000 μm. 6. The diamond-coated substrate according to claim 5, wherein the substrate is a wafer of one of silicon and molybdenum.