JP3212057B2 - Diamond coated substrate and method for producing the same - Google Patents

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 without warpage by canceling internal stress generated in the diamond film during film formation, or a diamond film peeled 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 of diamond, 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 developed. When a diamond film is formed directly from the gas phase on a tool substrate, depending on the method, stress caused by the difference in the coefficient of thermal expansion between the material of the substrate and diamond, that is, when coating the substrate with the diamond film, and after coating, The diamond film peels off from the substrate due to the residual stress generated by the temperature difference during cooling, and is hardly practical. On the other hand, after coating a specific substrate with diamond in advance by a vapor phase synthesis method, a method of brazing the obtained diamond-coated substrate to a tool so that the substrate and the tool are in contact with each other, or the diamond surface and the tool are in contact with each other. As described above, a method of polishing and removing the substrate after brazing to the tool or a method of peeling the diamond film from the diamond-coated substrate and brazing only the diamond film to the tool are also performed. In these methods, the residual stress increases as the thickness of the diamond film increases, and when the substrate is thin, the diamond-coated substrate warps. When warpage occurs, it takes many troubles to polish the film surface flat, or the diamond film tends to be broken when brazing to a tool, which causes many disadvantages. When forming a diamond film on a substrate, the film is formed in multiple stages for the purpose of improving adhesion, and the deposited film is formed into a multilayer structure, for example, JP-A 1-167211 and JP-A 3-197677. And Japanese Patent Application Laid-Open No. 4-99278, and further disclosed in Japanese Patent Application Laid-Open No.
No. 6195 is disclosed.

Japanese Patent Application Laid-Open 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 a lens or a window, or a protective film for a magnetic disk. By periodically changing the energy, the concentration of the carbon source, and the reaction pressure, a diamond-like carbon layer having a high amorphous carbon content,
A diamond-like carbon film in which diamond-like carbon layers having a low content of amorphous carbon are alternately deposited in layers is obtained. However, the present invention aims to obtain a diamond-like carbon film having a smooth surface and high light transmittance, and to obtain a film having excellent surface smoothness without performing surface polishing such as lapping after forming the film. To
The outermost surface layer is excellent in surface smoothness, but needs to be a diamond-like carbon layer with a low content of amorphous carbon with low hardness, so it is used as a hard coating layer for tools, which is the object of the present invention. Has insufficient wear resistance and is not suitable.

Japanese Patent Application Laid-Open No. 3-197677 discloses that the composition of impurities in a first layer is lower than that in a second layer in a substrate of a cemented carbide, a cermet, a silicon nitride sintered body, or an aluminum oxide sintered body. A diamond coating tool coated with multiple layers of diamond having a high diamond particle diameter in the first layer and smaller than the diamond particle diameter in the second layer, and a method for producing the same are disclosed. According to the present invention, it is necessary to form the first layer by using a filament CVD method and then form the second layer by using a plasma CVD method. In addition, there is a problem that the productivity is low and impurities such as dust adhere to the surface of the film after the formation of the film of the first layer, which may cause defects in the film of the second layer.

JP-A-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 at least one layer having a thickness of 0.5 to 200 μm. A diamond-coated tool member in which a plurality of diamond coating layers are formed on a hard material is disclosed. The present invention provides a diamond layer rich in toughness between a diamond layer containing no carbon component other than diamond and a substrate, containing a carbon component of the same component as diamond in the form of amorphous carbon.
The purpose of the present invention is to reduce the impact applied to the entire coating layer and to achieve both peeling resistance and abrasion resistance. However, there is a problem that as the thickness of the film increases, the stress generated in the film increases, and the film tends to peel off.

[0006] Japanese Patent Application Laid-Open No. 5-306195 discloses that a film-forming surface of a substrate on which a diamond film is deposited has a radius of curvature that compensates for the internal tensile stress expected in a diamond thin film obtained by removing the film from the substrate. Disclosed is a method of manufacturing a CVD diamond thin film that has a convex shape and has a thin film removed from a substrate, which is released from its internal tensile stress by warping in a direction opposite to the curvature of the substrate to release its internal tensile stress. I have. The present invention predicts in advance the degree of warpage of a film caused by internal stress in a film when depositing a diamond film on a substrate, and forms a flat film after peeling the film from the substrate and releasing the internal stress. In addition, the base material is characterized in that the base material is formed in a convex shape so as to cancel the warpage of the film in advance. However, since the internal stress generated in the film changes depending on the film forming apparatus and the film forming conditions, such as the increase in the film forming speed as the film forming speed increases, the film forming conditions of the diamond film should be adjusted according to the degree of the convex surface of the base material. It needs to be strictly controlled and is not practical.

[0007]

SUMMARY OF THE INVENTION In the present invention, a diamond film having a thickness of 5 to 2000 μm is formed using a vapor phase synthesis method without warping the film, and the film surface after the film formation is made flat. An object of the present invention is to provide a diamond-coated substrate which is easy to be polished, is hardly cracked when brazed to a tool, and has excellent adhesion, and a method for producing the same.

[0008]

According to the present invention, in a step of forming a diamond film on a substrate which is a wafer of one of silicon and molybdenum by a vapor phase synthesis method, the temperature of the substrate is changed by changing the temperature of the substrate. It changes the stress state generated inside the diamond film formed on the substrate, alternately generates compressive stress and tensile stress inside the diamond film, cancels out the internal stress generated in the diamond film, and flattens the diamond-coated substrate without warpage. And a diamond coated substrate manufactured by a vapor phase synthesis method, wherein the flatness of the diamond coated substrate manufactured by a vapor phase synthesis method is 8 m in a radius of curvature. As described above, the present invention provides a diamond-coated substrate having a diamond film thickness of 5 to 2000 μm. In the present invention, when a diamond film is formed using the same microwave power in the same component and the same concentration of working gas, the internal stress generated in the film at a certain substrate temperature is a tensile stress. It has been found that the pressure is reversed from the compression stress or from the compression stress to the tensile stress. As a result, the film is formed at a substrate temperature at which a compressive stress occurs during the formation of the diamond film, and subsequently the substrate temperature is changed to form a film at a substrate temperature at which a tensile stress occurs during the formation of the film, or as opposed to the above. A diamond film is formed using a heating cycle of the substrate, or by repeating this heating cycle several times to offset the tensile stress and the compressive stress generated in the film, thereby forming a thick film without warping the film. It is possible to form a diamond film.

Hereinafter, the present invention will be described in detail. Examples of the substrate on which the diamond film is formed by the vapor phase synthesis method of the present invention include metals such as silicon, molybdenum, tungsten, niobium, iron, copper, silver, and nickel; nonmetals such as graphite and boron; silicon carbide; Metal carbides such as tungsten, metal oxides such as alumina and silica, and nitrides such as boron nitride and silicon nitride can be used, but those having a small difference in expansion coefficient from diamond deposited on a substrate are preferable and economical. From the viewpoint of performance and practicality, a silicon or molybdenum wafer is suitable as a substrate on which the diamond film of the present invention is formed.

Next, after the above substrate surface is roughened by using emery paper or the like, a diamond film is formed by a gas phase synthesis method in a working gas composed of hydrogen and hydrocarbon. Microwave plasma CVD method as the gas phase synthesis method,
A filament CVD method, a DC plasma CVD method, an RF plasma CVD method, or the like can be applied.
It is preferable to use Method D. Examples of hydrocarbons serving 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 and aromatic compounds such as benzene and toluene can be used, use of methane is preferred in terms of economy and practicality. These hydrocarbons are mixed with hydrogen in a volume ratio of 1: 500 to 1: 5.
If the volume ratio is 1: 500 or less, the deposition rate of the diamond film becomes extremely low. In some cases, an inert gas such as argon may be further mixed with the mixed gas for dilution. The gas mixture is 0.
It is fed into the reactor at a pressure of 1 to 200 Torr. If the pressure is less than 0.1 Torr, the diamond is not deposited, and the substrate is etched. Apply microwave power of 100-5000W in this working gas,
A diamond film is formed on a substrate at a film forming speed of 0.1 to 15 μm. When the microwave output is 100 W or less, the deposition rate of the film becomes extremely low.On the other hand, when the microwave output is 5000 W or more, the deposition rate of the film improves, but the stress generated in the film increases and the warpage of the film increases. It is extremely difficult to obtain a flat diamond film without warping even with the film forming method for suppressing warping described in (1).

Then, within the above-mentioned conditions for forming the film, the conditions are fixed at a suitable level for obtaining a diamond film, and the substrate temperature is changed in a plurality of vapor-phase synthesis steps, and the temperature is generated in the diamond film in each step. Cancels compressive or tensile stress and forms a diamond film without warpage. The substrate temperature depends on the material of the substrate and the film forming conditions other than the substrate temperature, but it is 600 to 850 ° C. for applying a compressive stress to the film, and 880 to 1800 for applying a tensile stress to the film.
Keep it in the range of 100 ° C. When the substrate temperature is 600 ° C. or lower, the deposition rate becomes extremely low, and when the substrate temperature is 1100 ° C. or higher, graphite is eutectoid, which is not preferable. Further, it is preferable that the ratio of the thickness of the film formed in each stage of the vapor phase synthesis be within 3 times in order to obtain a film having a curvature radius of 8 m or more and having virtually no warpage. After the film is formed, the surface of the film is lapped and polished for flattening.If the radius of curvature is 8 m or less, the shaving margin for flattening the film becomes extremely large, which is disadvantageous in terms of cost, and also required for lapping. Since the time becomes long, the radius of curvature is preferably 8 m or more, more preferably 20 m or more. The lower limit of the film thickness is 5 μm to ensure sufficient abrasion resistance of the tool coated with the film, and to secure a margin for polishing the film flat after the film is formed, and the film forming time is required. The upper limit is set to 2000 μm from the viewpoint of time and economy.

As a method of canceling the internal stress generated in the diamond film by controlling the film forming conditions, other than the method of changing the substrate temperature as described above, the component ratio, concentration, and pressure of the working gas are changed. This can be achieved by a method or a method of changing the output of microwaves. However, as in the present invention, the method of changing the substrate temperature while fixing other variables is the most reliable and easy to achieve the object. can do.

[0013]

In the present invention, in the vapor phase synthesis of a diamond film, the component, concentration, pressure and microwave output of the working gas are kept constant, the substrate temperature is changed in a plurality of gas phase synthesis steps, and a compressive stress or By selectively and alternately generating tensile stress to offset the compressive stress and the tensile stress, a thick diamond film is formed without causing the film to warp. According to this method, the diamond-coated substrate can be formed into a flat shape without warpage.

[0014]

The present invention will be described in more detail with reference to the following examples. (Example) As a substrate for diamond coating, a thickness of 0.62
5mm, 25mm square silicon wafer and molybdenum wafer were selected. The surface of the wafer was polished and roughened with ^# 240 emery paper, and then ultrasonically cleaned in acetone.
Microwave plasma CVD on the pretreated wafer
The substrate was heated under the conditions shown in Tables 1 to 4 in an atmosphere consisting of 1150 W, a hydrogen flow rate of 95 SCCM (cm ³ / min) and a methane flow rate of 5 SCCM under an operating pressure of 90 Torr by using the method, and a diamond film was formed. . The warping 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 Pythagorean theorem. Tables 5 to 8 show the results.
Shown in

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

[Table 6]

[0021]

[Table 7] (Note) ^* : The film thickness is thin, and the abrasion resistance is poor when applied to cutting tips.

[0022]

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

As shown in 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 and 8, when the diamond film is formed with only one layer as shown in Comparative Examples 2 and 3, the film is warped due to internal stress generated in the film, The film may not be able to withstand stress and may be destroyed immediately after film formation. Further, as shown in Comparative Example 5, even when the film is formed in a structure including 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 abrasion 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 not practical.

[0024]

As described above, according to the present invention, it is possible to form a diamond-coated substrate having a large thickness in a flat shape without warping, and to polish the diamond film surface after film formation. Is easier, and
The diamond film can be brazed to the tool without causing the film to crack.

Claims (5)

(57) [Claims] In a step of forming a diamond film on a substrate by a plasma CVD method, compressive stress and tensile stress are alternately generated inside the formed diamond film, thereby canceling the internal stress generated in the diamond film, A method for producing a diamond film, wherein the diamond-coated substrate has a flat shape without warpage. 2. Changing the temperature of the substrate to change the stress state generated inside the diamond film formed on the substrate, thereby causing the compressive stress and the tensile stress to be alternately generated inside the diamond film to cause the internal stress generated in the diamond film. The method for producing a diamond film according to claim 1, wherein the stress is offset. 3. The substrate temperature for generating the compressive stress is 600 to 850 ° C. and the substrate temperature for generating the tensile stress is 3.
The method for producing a diamond film according to claim 1, wherein the temperature is 880 to 1100 ° C. 4. 4. The method according to claim 1, wherein the substrate is a wafer of one of silicon and molybdenum.
2. The method for producing a diamond film according to any one of 2 and 3. 5. The method according to claim 1, wherein the thickness of the diamond film coated on the substrate is 5 to 2000 μm.
2. The method for producing a diamond film according to any one of 2, 3, and 4.