JPH06170571A - Laser polishing method for diamond and device and diamond product formed by utilizing this method and device - Google Patents

Abstract

PURPOSE:To provide the laser polishing method having excellent efficiency of polishing of a diamond surface and the device to be used in this method as well as the diamond product. CONSTITUTION:The surface 3 of a diamond thin film 1 formed on a substrate 2 is irradiated with a laser beam 6 from a diagonal direction so as to form a focus 7 around this surface. A mirror 9 is so turned that the surface of the thin film 1 is scanned with the focus 7 of the laser beam along straight lines L. A table is then moved and the adjacent straight lines L2, L3,... are successively scanned. Then, the projecting parts 4 on the surface of the thin film 1 are successively removed at the focus 7 of a high energy density and, therefore, the polishing efficiency is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser polishing method for a diamond thin film used for a cutting tool, a knife, a heat sink substrate material, etc., an apparatus for carrying out the method, and a diamond product using the method.

[0002]

2. Description of the Related Art Recently, a cutting tool has been proposed in which a diamond thin film formed by a vapor phase synthesis method is fixed to a base material. Since the diamond thin film formed by this vapor phase synthesis method has large irregularities on the surface, it is necessary to polish the surface using, for example, diamond particles. However, since this method has a slow polishing rate, even a small diamond requires a long polishing time. Therefore, in order to shorten the polishing time, a polishing method has been proposed in which the surface of the deposited diamond is processed to be smooth by using a laser beam having a high energy density (Japanese Patent Laid-Open No. 3-264).
181 and JP-A-3-272810).
In this polishing method, as shown in FIG. 9, first, the side surface 104 of the laser beam 103 focused in a conical shape by the convex lens 102 is arranged in parallel with the vicinity of the end of the deposited diamond 101. Then, the laser beam is relatively moved along the designed polishing surface while removing the convex portion 101a by heat (arrow X). When the polishing of the strip-shaped region R1 at the end is completed, the table 105 is moved in the direction of the arrow Y, and the next strip-shaped region R2 is similarly polished.

[0003]

The conventional polishing method has the advantage that the width W of the region that can be polished at one time is relatively large, about 300 μm, but it is polished on the side surface of the laser beam having a low energy density. It has the disadvantage of low efficiency. Therefore, the moving speed of the laser beam cannot be increased, and for example, the average output is 8 W and the pulse frequency is 1
It takes about 20 minutes to smooth the surface roughness of the deposited diamond thin film having an area of 7 mm × 3 mm to Rmax = 3 μm at kHz.

An object of the present invention is to improve the conventional method for polishing a diamond by a laser, to improve the polishing efficiency to increase the processing speed, and to provide an apparatus for carrying out the method.

[0005]

According to the method of laser polishing a diamond of the present invention, a laser is obliquely irradiated to a surface of a diamond so that a focal point near the surface of the diamond is focused, and the focal point of the laser is on the surface of the diamond. It is characterized by giving a relative motion to both so as to scan. In such a method, it is preferable to perform the scanning by changing the irradiation angle of the laser. Further, it is preferable to irradiate the laser in pulse form and to control the pulse width according to the speed at which the laser focus moves on the surface of the diamond. The laser polishing apparatus of the present invention is provided with a table on which a workpiece including diamond is placed, and a laser that is arranged to irradiate the table with a laser obliquely and to focus on the surface of the workpiece. A laser irradiation source, a table driving device that causes a one-dimensional movement of the table parallel to the surface of the table, and a laser irradiation source driving device that scans a focus by swinging the laser irradiation direction. It is characterized by In such a device, it is preferable that the table drive device reciprocates the table, and the table drive device rotationally drives the table about an axis perpendicular to the surface thereof. It is preferable that the laser irradiation source driving device scans the focal point of the laser in the radial direction. The diamond product of the present invention comprises a substrate and a diamond thin film formed on the substrate by a vapor phase synthesis method, and the outer protruding surface of the diamond thin film is polished smoothly by any of the above methods. Is characterized by. Furthermore, the cutting tool of the present invention is characterized in that such a diamond product is attached such that the polishing surface is on the outside.

[0006]

According to the method of the present invention, the surface of the precipitated diamond is irradiated with the laser so that the vicinity of the surface is focused, so that the processing can be performed at the focus having the highest energy density. Therefore, the polishing rate can be made much faster than the conventional method. Moreover, since the irradiation is performed from an oblique direction, preferably from a direction of 45 degrees or less, the problem of partially making holes (defects) on the surface is avoided,
Only the protrusions on the surface of the deposited diamond can be efficiently removed. In the method of the second aspect, the scanning is performed by shaking the laser beam, so that the processing speed can be further increased. In the method of claim 3, since the laser is irradiated in a pulsed manner and the pulse width is controlled according to the relative moving speed of the laser and the diamond, the surface can be irradiated with the pulse at a uniform pitch. . Therefore, a scanning method in which the relative moving speed changes can be freely adopted. In the apparatus of the present invention according to claim 4, the table is caused to perform a one-dimensional movement and is oscillated around one axis in the direction of laser irradiation. Therefore, the relative movement of the two causes the focus of the laser to move along the surface of the object to be processed. Perform a dimensional scan. Therefore, high-speed flat or curved surface polishing can be performed with a simple scanning mechanism. In the apparatus according to the fifth aspect, the table rotates, and the focal point of the laser is scanned in the radial direction of the table. Therefore, the focal point performs polishing while drawing a "spiral-shaped" locus as a whole. In this case, the rotation speed of the table may be gradually changed and the pulse width of the laser may be changed. The diamond product of the present invention has the advantage that the product durability is high because the diamond deposition surface, which has high hardness and is dense, is located outside. Since the cutting tool of the present invention is mounted with the diamond product polished by the above-mentioned method so that the smooth polished surface faces outward, the cutting tool has good sharpness and high durability.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and apparatus of the present invention will be described below with reference to the drawings. 1 is a process explanatory view showing an embodiment of the method of the present invention, FIG. 2 is an enlarged view of the step a in FIG. 1, FIG. 3 is an overall layout drawing showing an embodiment of the apparatus of the present invention, and FIG. 4 is a book. FIG. 6a is a perspective view showing an embodiment of a table relating to the apparatus of the invention, and FIGS. 5a and 5b are sectional views before and after processing showing an embodiment of the diamond product of the present invention, respectively.
And FIG. 6b are enlarged cross-sectional views showing the surface states of the diamond thin film before and after polishing by the method of the present invention, FIG. 7 is an enlarged perspective view of the diamond thin film polished by the method of the present invention, and FIG. 8 is the present invention. It is a perspective view which shows one Example of the cutting tool of.

First, the method of the present invention will be described with reference to FIGS. 1 in FIG. 1 is a diamond thin film (hereinafter referred to as a thin film) formed on a silicon substrate 2 by a vapor phase synthesis method.
Is. The free surface 3, that is, the deposition surface has a high hardness because there are few impurities and voids, but a large number of convex portions 4 are projected. In the case of FIG. 1, the convex portion 4 is removed by focusing the laser beam 6 focused by the convex lens 5 on the surface 3 of such a thin film 1. In the embodiment of FIG. 1a, the optical axis 8 of the laser beam 6 is further inclined at an angle (irradiation angle) θ with respect to the surface 3, so that the projection 4 is irradiated obliquely from the lateral side. The irradiation angle may be larger. However, when it becomes 90 degrees, not only the convex portion 4 is removed, but also holes are formed in the surface 3 to cause a surface defect, so the angle is set to less than 90 degrees. That is, in the claims, “irradiate from an oblique direction” means that θ in FIG. 1A is 0 ° <θ <9.
It means in the range of 0 degree. Incidentally, reference numeral 9 in FIG.
Is a schematic representation of a galvanometer mirror for scanning the laser beam along the surface of the thin film 1.

In the embodiment of FIG. 1, while maintaining the basic polishing mode shown in FIG. 1a, the focal point 7 is secondarily scanned on the surface of the thin film 1 to polish the entire surface. The scanning method is, for example, by swinging the galvanometer mirror 9 shown in FIG.
As shown in FIG. 2, the focal point 7 is moved by swinging the laser beam 6 in the vertical direction, that is, in the direction (arrow S) along the intersection line L between the plane P including the laser beam 6 and perpendicular to the thin film 1 and the thin film surface. Scan along the surface. Further, when the polishing along the intersecting line is completed in this way, as shown in FIG. 1c, the material having the thin film 1 is displaced in the direction of the arrow N, and polishing is performed along the next adjacent straight line L2. Further, similarly, polishing is sequentially advanced in order of L3, L4, .... Figure 1
After polishing in one direction of c, the object is further rotated 90 degrees,
The polishing may be performed in two directions as a whole (FIG. 1d). It is also possible to install another galvano mirror having an axis formed in a direction perpendicular to the axis 10 of the galvano mirror 9 and scan the laser beam two-dimensionally instead of shifting the material in the direction of the arrow N. Is. When the laser beam is shaken as shown in FIG. 1b, strictly speaking, the focal point 7 does not hit the surface unless the focal length Fr of FIG. 2 is changed accordingly.
However, if the focal length Fr is large, for example, 200 mm
In the above case, there is almost no problem compared with the size of the thin film (for example, a square having a side of 16 mm). Moreover, when the diameter of the laser beam at the focal point 7 is about 0.06 to 0.1 mm, the area R of 1 to 5 mm before and after the focal point 7 in FIG. Therefore, it suffices to scan the laser beam 6 by simply shaking it with the galvanometer mirror 9 or the like without moving it in parallel. In FIGS. 1b and 1c, the laser-polished portion is shown as a discontinuous region R on the surface of the thin film 1, which means that the laser beam is applied in a pulsed manner. When pulsed irradiation is performed discontinuously in this way, the peak value output reaches about 1000 times that during continuous oscillation, and there is an effect that a sufficient power density for polishing the diamond surface can be obtained. Further, as will be described later, even if the moving speed of the focus changes due to the driving method of the two-dimensional relative motion, there is an advantage that uniform polishing can be easily performed by controlling the pulse width.

A preferred embodiment of an apparatus for carrying out the polishing method will be described with reference to FIGS. Figure 3
No. 11 is a laser generation source including an optical system and a Q switch, which adopts a galvanometer type optecasul caner system in which scanning is performed by a galvanometer mirror. The beam diameter of the laser near the focus is, for example, 0.06 to 0.1 m.
m. The Q switch is for controlling the pulse width. Such a laser source (laser irradiation device)
A power supply box 12 including a Q switch driver sends a power for laser oscillation and a signal for controlling the Q switch to 11. Further, the laser source 11 and the power supply box 12 are controlled by a controller 13 including a personal computer. Further, a table 14 on which the object to be polished is placed is arranged facing the beam irradiation port 11a of the laser generation source 11.

FIG. 4 shows an embodiment of a table on which an object to be polished (silicon substrate 2 having a diamond thin film on the surface) is placed. In this embodiment, a turntable 16 rotating around a shaft 15 is adopted. is doing. In the case of the present embodiment, the irradiation angle of the laser beam 6 is swung in the S direction and scanning is performed in the radial direction. Therefore, the scanning speed can be increased. When the laser beam is swung in the direction of arrow S while rotating the turntable 16 in the direction of arrow A, the focal point 7 polishes the surface of the thin film 1 while drawing a spiral or concentric locus 17. The rotation speed of the turntable 16 and the pulse frequency may be constant or may be changed.
That is, the length of the vortex winding per rotation of the turntable 16 becomes shorter as the focus approaches the inner side of the radius,
For example, the relative movement speed of the focus 7 may be made uniform by gradually increasing the number of revolutions of the turntable 16 so that the irradiation amount of the laser beam per line length is made uniform. Further, the irradiation amount per line length of the laser beam may be made uniform by gradually increasing the pulse width through the control of the Q switch.

By performing the polishing process with the laser beam, the diamond thin film shown in FIG. 5A is smoothed as shown in FIG. 5B. The method of the present invention is used when the surface irregularities are large, such as when a diamond thin film is formed on a silicon substrate by a vapor phase synthesis method.
It can be used for smoothing the surface of a diamond thin film or a diamond piece formed by another manufacturing method. Substrates other than silicon may also be used.

As the vapor phase synthesis method of diamond, any method such as a thermionic emission material method, a DC arc discharge method, a DC glow discharge method, a microwave discharge method, or a high homowave discharge method can be used. A YAG laser (yttrium argon garnet laser) usually used for laser processing is preferable as the laser source, but other types of lasers may be used. Next, the method of the present invention will be described with reference to specific examples.

Example 1 A silicon thin film having a thickness of 300 μm was formed on a silicon substrate by a microwave discharge method using a (100) plane of 8 mm square and a thickness of 0.3 mm. The conditions of the microwave discharge method at this time are that the hydrogen flow rate is 85 ml / min, the methane flow rate is 15 ml / min, and the operating pressure is 120 torr.
The substrate is forced water cooled, and the discharge power is 1000W and 10
Diamond was formed for 0 hours. The surface roughness of the obtained diamond thin film is shown in FIG. 6A. The vertical axis is 40 times larger than the horizontal axis. The surface roughness of the as-deposited diamond thin film is Ra (average roughness) = 5.8 μm, R
Max (maximum roughness) = 45.0 μm, and this was laser-polished under the following conditions. The laser used had a laser average output of 0 to 9 W and a Q switch frequency of 0.1.
It is a YAG laser of ˜50 kHz.

First, the object is placed on an XY table, and the angle θ between the laser optical axis and the table surface is 1 degree, 1 degree.
Maintain at 0, 20, 45, or 80 degrees, 8
After focusing on the center of a thin film of 8 mm × 8 mm, processing was performed at a marking speed (focus moving speed on the polishing surface) v = 10 mm / sec based on the swing of the mirror. At this time, since the pulse interval λ was set to 3.3 μm, v = λ · f
From (v: mm / sec, λ: μm, f: kHz), the Q switch frequency f becomes 3 kHz. The average output during processing was 6.4 W and the peak value output was 23.7 kw. Furthermore, using a wide-angle lens, the focal length of the laser beam is 2
It was set to 44 mm. The interval between adjacent processing lines, that is, the hatching interval was 5 μm. As a result, the total length of the entire processing line is 8 x 8 (area of silicon substrate) /
0.005 (hatching interval) = 12800 mm. Under the above processing conditions, the irradiation angle θ of the laser beam was changed, and processing was performed by one-way polishing (see FIG. 1c) and two-way polishing (see FIG. 1d).

Next, as a comparative example, the focal length of the laser beam is 50 mm (divergence angle of about 3 using a short focus lens.
0 degree) and processing was performed by moving the table at right angles to the laser beam with the side surface of the laser beam applied to the thin film surface by the conventional method as shown in FIG. Other conditions were the same as in the example. After processing by the method of the above embodiment,
The surface roughness was measured with a surface roughness meter. The results are shown in Table 1.
Shown in.

[0017]

[Table 1]

Incidentally, FIG. 6B shows a surface roughness curve based on a micrograph when polishing was performed under the condition of polishing four times with the irradiation angle of 10 degrees in the example, and a schematic perspective view based on the micrograph of the surface. Is shown in FIG. From the above results, in the method of the example, the surface roughness was Ra = 5.
8, Rmax = 45.0, Ra = 2.3-5.0,
It can be seen that remarkable smoothing was performed with Rmax = 15.5 to 40.1. Further, it is found that the irradiation angle θ is preferably small, and is preferably 45 degrees or less, particularly preferably about 1 to 20 degrees. Further, it can be seen that the two-way polishing reduces the surface roughness by almost half and achieves further smoothing, as compared with the one-way polishing.

Incidentally, in the conventional method, the processing time required about four times as long as that of the present invention in order to obtain the same polishing roughness.

From the above results, it is understood that the method of scanning the focus of the laser beam on the surface to be processed according to the present invention can perform the polishing process much more efficiently than the conventional method of applying the side surface of the laser beam. .

The diamond product polished by the method of the present invention is cut into, for example, an equilateral triangle having a side of 3 mm, and the diamond product shown in FIG.
It can be suitably used for various cutting tools such as the throw away tip 21 for the cutting tool 20 shown in FIG. Since this one can use the precipitation surface having high hardness as a cutting surface, it has an advantage of high sharpness and durability.

[0022]

According to the method of the present invention, since the focal point having a high energy density is scanned along the surface of the object to be polished, the processing efficiency can be increased to about 4 times that of the conventional method. The device of the present invention can efficiently carry out the method. The diamond product and the cutting tool of the present invention have the advantage of high durability and sharpness because the deposition surface with high hardness of the diamond thin film by the vapor phase synthesis method is used as the outer surface.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method of the present invention.

FIG. 2 is an enlarged view of step a in FIG.

FIG. 3 is an overall layout drawing showing an embodiment of the apparatus of the present invention.

FIG. 4 is a perspective view showing an embodiment of a table relating to the apparatus of the present invention.

FIG. 5a is a cross-sectional view before processing showing an embodiment of the diamond product of the present invention, and FIG. 5b is a cross-sectional view after processing.

6A and 6B are enlarged cross-sectional views showing the surface state of a diamond thin film before and after polishing by the method of the present invention, respectively.

FIG. 7 is a schematic perspective view of a diamond thin film surface polished by the method of the present invention.

FIG. 8 is a perspective view showing an embodiment of a cutting tool of the present invention.

[Explanation of symbols]

 1 ... Diamond 2 ... Silicon substrate 3 ... Surface 6 ... Laser beam 7 ... Focus 9 ... Galvanometer mirror 11 ... Laser source 12 ... Power supply box 13 ... Controller 14 ... Table 16 ... Turntable

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[Procedure amendment]

[Submission date] July 13, 1993

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method of the present invention.

FIG. 2 is an enlarged view of step a in FIG.

FIG. 3 is an overall layout drawing showing an embodiment of the apparatus of the present invention.

FIG. 4 is a perspective view showing an embodiment of a table relating to the apparatus of the present invention.

FIG. 5a is a cross-sectional view before processing showing an embodiment of the diamond product of the present invention, and FIG. 5b is a cross-sectional view after processing.

6A and 6B are enlarged cross-sectional views showing the surface state of a diamond thin film before and after polishing by the method of the present invention, respectively.

FIG. 7 is a schematic perspective view of a diamond thin film surface polished by the method of the present invention.

FIG. 8 is a perspective view showing an embodiment of a cutting tool of the present invention.

FIG. 9 is a schematic view showing a conventional polishing method.

[Explanation of Codes] 1 ... Diamond 2 ... Silicon substrate 3 ... Surface 6 ... Laser beam 7 ... Focus 9 ... Galvano mirror 11 ... Laser source 12 ... Power supply Box 13 ... Control device 14 ... Table 16 ... Turntable

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C30B 29/04 V 7821-4G

Claims (8)

[Claims] 1. A diamond which irradiates a diamond surface from an oblique direction so that a focal point near the surface of the diamond is focused, and gives a relative motion to both so that the focal point of the laser scans the surface of the diamond. Laser polishing method. 2. The method according to claim 1, wherein the scanning is performed by changing an irradiation angle of the laser. 3. The method of claim 1, wherein the laser is pulsed and the pulse width is controlled according to the speed at which the laser focus moves on the surface of the diamond. 4. A table on which a processing object having diamond is placed, and laser irradiation arranged so that the table is irradiated with a laser from an oblique direction and the surface of the processing object is focused. Laser polishing provided with a laser source, a table driving device that causes the table to make a one-dimensional movement parallel to the surface of the table, and a laser irradiation source driving device that scans a focus by swinging the irradiation direction of the laser. apparatus. 5. The device according to claim 4, wherein the table driving device reciprocates the table. 6. The table driving device drives the table to rotate about a vertical axis to the surface of the table, and the laser irradiation source driving device scans the laser focal point in the radial direction. 4. The device according to 4. 7. A substrate and a diamond thin film formed on the substrate by a vapor phase synthesis method, and an outer protruding surface of the diamond thin film is smoothly polished by the method according to claim 1, 2 or 3. A diamond product. 8. A cutting tool in which the diamond product according to claim 7 is attached so that the polishing surface is on the outside.