JP3096943B2 - Laser polishing method and apparatus for diamond and diamond product using 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 method for laser-polishing a diamond thin film used as a material for a cutting tool, a scalpel, a heat sink substrate, etc., an apparatus for carrying out the method, and a diamond product using the method.

[0002]

2. Description of the Related Art Recently, cutting tools have been proposed in which a diamond thin film formed by a vapor phase synthesis method is fixed to a substrate. 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, this method has a low polishing rate, so that the polishing process takes a long time even with a small diamond. Therefore, in order to shorten the polishing time, a polishing method has been proposed in which the surface of the precipitated diamond is processed smoothly 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, a side surface 104 of a laser beam 103 focused conically by a convex lens 102 near an end of a precipitated diamond 101 is arranged in parallel. Then, the laser beam is relatively moved along the designed polishing surface while removing the convex portion 101a by heat (arrow X). Further, when the polishing of the band-shaped region R1 at the end is completed, the table 105 is moved in the direction of the arrow Y, and the next band-shaped region R2 is polished in the same manner.

[0003]

The above-mentioned conventional polishing method has an advantage that the width W of a region that can be polished at once can be relatively large, about 300 μm, but it is polished on the side of a laser beam having a low energy density. There is a disadvantage of low efficiency. Therefore, the moving speed of the laser beam cannot be increased. 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 a deposited diamond thin film having an area of 7 mm × 3 mm at KHz to Rmax = 3 μm.

[0004] It is an object of the present invention to improve the above-mentioned conventional diamond polishing method using a laser, to increase the processing speed by improving the polishing efficiency, and to provide an apparatus for performing the method.

[0005]

According to a first aspect of the present invention, there is provided a method of polishing a diamond by irradiating a laser to a surface of the diamond obliquely so as to focus on the vicinity of the surface of the diamond. The method is characterized in that the diamond is moved upward so that the diamond is displaced so that the two are relatively moved to remove the projections formed on the diamond surface at the focal point of the laser. The method of claim 2 is a method according to claim 1,
The diamond is polished in two directions by rotating the diamond at right angles. According to a third aspect of the present invention, in the method of the first aspect, the diamond is rotated to perform the spiral polishing. A laser polishing apparatus according to a fourth aspect is an apparatus for performing the method according to any one of the first to third aspects, and a table on which an object to be processed having diamond is placed, and an oblique direction with respect to the table. A laser irradiation source arranged so as to irradiate a laser beam from the laser beam and to focus on the surface of the object to be processed; a table driving device for causing the table to generate a one-dimensional movement parallel to the surface of the table; And a laser irradiation source driving device that scans the focal point by oscillating the irradiation direction, and removes the convex portion formed on the diamond surface at the focal point. The device according to claim 5 is characterized in that the table driving device reciprocates the table. 7. The apparatus according to claim 6, wherein the table driving device drives the table to rotate around an axis perpendicular to the surface thereof, and the laser irradiation source driving device scans the focal point of the laser in a radial direction. It is characterized by. The diamond product according to claim 7 comprises a substrate and a diamond thin film formed on the substrate by a vapor phase synthesis method, wherein the outer bent surface of the diamond thin film is claimed.
Alternatively, it is characterized by being polished smoothly by the method described in 3. The cutting tool according to claim 8 is characterized in that the diamond product according to claim 7 is attached so that the polished surface is on the outside.

[0006]

In the method of the present invention, the surface of the precipitated diamond is irradiated with laser so as to focus on the vicinity of the surface, so that the processing can be performed with the focal point having the highest energy density. Therefore, the polishing rate can be made much faster than the conventional method. In addition, since irradiation is performed in an oblique direction, preferably in a direction of 45 degrees or less, a problem that a hole (defect) is partially formed in the surface is avoided.
Only the protrusions on the surface of the precipitated diamond can be efficiently removed. In the method according to the second aspect, since the scanning is performed by shaking the laser beam, the processing speed can be further increased. In the method according to the third aspect, the laser is irradiated in a pulse shape, and the pulse width is controlled in accordance with the relative moving speed between the laser and the diamond, so that 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 according to the fourth aspect of the present invention, the table is caused to perform one-dimensional movement, and at the same time, is swung about one axis in the direction of laser irradiation. 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, since the table is rotated and the focal point of the laser is scanned in the radial direction of the table, the focal point is polished while drawing a "spiral-shaped" locus as a whole. In this case, the rotation speed of the table may be gradually changed, or the pulse width of the laser may be changed. The diamond product of the present invention has an advantage of high product durability because the diamond has a high hardness and a dense diamond deposition surface on the outside. The cutting tool of the present invention has good sharpness and high durability because the diamond product polished by the above method is attached so that the smooth polished surface is on the outside.

[0007]

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

First, the method of the present invention will be described with reference to FIGS. 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.
It is. The free surface 3, that is, the deposition surface has high hardness because of few impurities and voids, but has many convex portions 4 protruding. 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 the thin film 1. In the embodiment of FIG. 1 a, 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 from an oblique side. This irradiation angle may be larger. However, when the angle is 90 degrees, not only the protrusions 4 are removed but also a hole is formed in the surface 3 and a surface defect is caused. That is, “irradiation from an oblique direction” in the claims means that θ in FIG. 1A is 0 degree <θ <9.
It is within the range of 0 degrees. Note that reference numeral 9 in FIG.
1 schematically shows a galvano mirror for scanning a laser beam along the surface of the thin film 1.

In the embodiment shown in FIG. 1, the focal point 7 is secondarily scanned on the surface of the thin film 1 while the basic polishing mode shown in FIG. The scanning method is, for example, to swing the galvanomirror 9 of FIG.
As shown in FIG. 5, the focal point 7 is moved in the vertical direction, that is, in the direction (arrow S) along the intersection L between the plane P containing the laser beam 6 and perpendicular to the thin film 1 and the surface of the thin film 1 to move the focal point 7 to the thin film 1. Scan along the surface. Further, when the polishing along the intersection line is completed, the material having the thin film 1 is shifted in the direction of arrow N as shown in FIG. 1C, and is polished along the next adjacent straight line L2. Then, the polishing is sequentially performed in the order of L3, L4, and so on. FIG.
After polishing in one direction of c, the object is further rotated by 90 degrees,
Polishing may be performed in two directions as a whole (FIG. 1d). It is also possible to install another galvanometer mirror having an axis perpendicular to the axis 10 of the galvanometer mirror 9 and scan the laser beam two-dimensionally instead of shifting the material in the direction of the arrow N. It is. When the laser beam is oscillated as shown in FIG. 1B, strictly speaking, the focal point 7 does not hit the surface unless the focal length Fr in FIG. 2 is changed accordingly.
However, when the focal length Fr is large, for example, 200 mm
In the above case, there is almost no problem compared to the size of the thin film (for example, a square having a side of 16 mm). In addition, when the laser beam diameter at the focal point 7 is about 0.06 to 0.1 mm, sufficient polishing can be performed in the region R of 1 to 5 mm before and after the focal point 7 in FIG. Therefore, it is sufficient to scan the laser beam 6 by simply shaking it with the galvanomirror 9 or the like without moving it in parallel. In FIGS. 1B and 1C, the laser-polished portion is indicated as a discontinuous region R on the surface of the thin film 1, which means that the laser beam is irradiated in a pulse shape. When the pulse is discontinuously irradiated in this manner, the peak value output reaches about 1000 times that of the continuous oscillation, and there is an effect that a power density sufficient for polishing the diamond surface can be obtained. Further, as described later, even when the moving speed of the focal point is changed by 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.

Next, referring to FIGS. 3 and 4, a preferred embodiment of an apparatus for carrying out the polishing method will be described. FIG.
Reference numeral 11 denotes a laser generation source including an optical system and a Q switch, which employs a galvanometer-type opt-castle canna system that scans with a galvanometer mirror. The beam diameter of the laser near the focal point 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)
For 11, power for laser oscillation and a signal for controlling the Q switch are sent from a power supply box 12 including a Q switch driver. Further, the laser source 11 and the power supply box 12 are controlled by a control device 13 including a personal computer. Further, a table 14 on which an object to be polished is placed is arranged opposite to the beam irradiation port 11a of the laser source 11.

FIG. 4 shows an embodiment of a table for placing an object to be polished (silicon substrate 2 having a diamond thin film on the surface). In this embodiment, a turntable 16 which rotates around an axis 15 is employed. doing. In the case of the present embodiment, scanning is performed in the radial direction by changing the irradiation angle of the laser beam 6 in the S 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 trajectory 17. The rotation speed of the turntable 16 and the frequency of the pulse may be constant or may be changed.
That is, as the focal point approaches the inside of the radius, the length of the spiral winding per rotation of the turntable 16 decreases,
For example, by gradually increasing the rotation speed of the turntable 16, the relative movement speed of the focal point 7 may be made uniform, and the irradiation amount per line length of the laser beam may be 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 using 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 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 diamond piece formed by another manufacturing method. Substrates other than silicon can also be used.

As the diamond vapor phase synthesis method, any method such as a thermionic emission method, a DC arc discharge method, a DC glow discharge method, a microwave discharge method or a high-frequency discharge method can be used. The laser source is preferably a YAG laser (yttrium argon garnet laser) usually used for laser processing, but may be another type of laser. Next, the method of the present invention will be described with reference to specific examples.

Example 1 A (100) plane having a thickness of 8 mm square and a thickness of 0.3 mm was used as a silicon substrate, and a 300 μm-thick diamond thin film was formed on the silicon substrate by a microwave discharge method. At this time, the conditions of the microwave discharge method are as follows: hydrogen flow rate is 85 ml / min, methane flow rate is 15 ml / min, operating pressure is 120 torr,
The substrate was forced water cooled, and the discharge power was 1000 W for 10
Diamond was formed for 0 hours. FIG. 6A shows an uneven state of the surface of the obtained diamond thin film. The vertical axis is enlarged to 40 times 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 subjected to laser polishing under the following conditions. The laser used was laser average output 0-9W, Q switch frequency 0.1
-50 kHz YAG laser.

First, the object is placed on an XY table, and the angle θ between the optical axis of the laser and the table surface is set to 1 degree, 1 degree.
Maintain at 0 degree, 20 degree, 45 degree, 80 degree, 8
After focusing on the center of the thin film of 8 mm × 8 mm, the film was processed at a marking speed (focal moving speed on the polished 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
(V: mm / sec, λ: μm, f: kHz), the Q switch frequency f is 3 kHz. The average output during processing was 6.4 W and the peak output was 23.7 kW. Using a wide-angle lens, the focal length of the laser beam is 2
44 mm. The interval between the adjacent processing lines, that is, the hatching interval was 5 μm. Thus, the total length of the entire processing line is 8 × 8 (the area of the silicon substrate) /
0.005 (hatching interval) = 12800 mm. Under the above processing conditions, processing was performed by one-way polishing (see FIG. 1C) and two-way polishing (see FIG. 1D) while changing the irradiation angle θ of the laser beam.

Next, as a comparative example, using a short focus lens, the focal length of the laser beam was set to 50 mm (the spread angle was about 3 mm).
0 °), and the table was moved by a conventional method as shown in FIG. 9 while moving the table at right angles to the laser beam while the side surface of the laser beam was in contact with the thin film surface. 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. Table 1 shows the results.
Shown in

[0017]

[Table 1]

FIG. 6B shows a surface roughness curve based on a micrograph when polishing was performed under the conditions of four times polishing at an irradiation angle of 10 degrees in the example, and a schematic perspective view based on the micrograph of the surface is shown. Is shown in FIG. From the above results, in the method of the embodiment, the surface roughness was Ra = 5.
8, from Rmax = 45.0, Ra = 2.3 to 5.0,
Rmax = 15.5 to 40.1, which indicates that remarkable smoothing was performed. It is also understood that the smaller the irradiation angle θ is, the smaller the angle is, preferably 45 degrees or less, and particularly preferably about 1 to 20 degrees. Further, it can be seen that the surface roughness is almost halved in the two-way polishing compared to the one-way polishing, and further smoothing is achieved.

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

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

The diamond product polished by the method of the present invention is cut into a regular triangle having a side of 3 mm, for example, as 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. This has the advantage that the sharpness and durability are high because the precipitation surface having high hardness can be used as the cutting surface.

[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 made about four times that of the conventional method. The device of the present invention can efficiently perform the above method. ADVANTAGE OF THE INVENTION Since the diamond product and cutting tool of this invention use the precipitation surface with high hardness among the diamond thin films by a vapor phase synthesis method for an outer surface, there exists an advantage with high durability and sharpness.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a step a in FIG. 1;

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diamond 2 ... Silicon substrate 3 ... Surface 6 ... Laser beam 7 ... Focus 9 ... Galvano mirror 11 ... Laser generation source 12 ... Power supply box 13 ... Controller 14 ・ ・ ・ Table 16 ・ ・ ・ Turntable

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B28D 5/00 B28D 5/00 Z C30B 29/04 C30B 29/04 V 33/00 33/00 (56) References JP 3-272810 (JP, A) JP-A-4-331800 (JP, A) JP-A-6-40797 (JP, A) JP-A-2-15625 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00-26/38 B24B 9/16 B28D 5/00 C30B 29/04 C30B 33/00

Claims (8)

(57) [Claims] 1. A laser is applied obliquely to the surface of a diamond so as to focus on the vicinity of the surface, and the laser is scanned on the surface of the diamond and the diamond is shifted so that the diamond is shifted relative to both surfaces. A laser polishing method for diamond in which a convex portion formed on a diamond surface is removed at a focal point of a laser so as to give a dynamic movement. 2. The method of claim 1, wherein the polishing is performed in two directions by rotating the diamond at right angles. 3. The method according to claim 1, wherein the spiral polishing is performed by rotating the diamond. 4. An apparatus for carrying out the method according to claim 1, wherein a table on which a workpiece having diamond is placed is irradiated with a laser from an oblique direction. Laser irradiation source arranged so as to focus on the surface of the object to be processed, a table driving device that causes the table to generate a one-dimensional movement parallel to the surface of the table, and the irradiation direction of the laser. A laser polishing apparatus comprising: a laser irradiation source driving device configured to scan a focal point by swinging the laser beam and remove a convex portion formed on the diamond surface at the focal point. 5. The apparatus according to claim 4, wherein the table driving device reciprocates the table. 6. The table driving device for driving the table to rotate about an axis perpendicular to the surface thereof, and the laser irradiation source driving device scans a focal point of the laser in a radial direction. An apparatus according to claim 4. 7. A method according to claim 1, comprising a substrate and a diamond thin film formed on the substrate by a vapor phase synthesis method, wherein the bent out surface of the diamond thin film is polished smoothly by the method according to claim 1, 2 or 3. Diamond products. 8. A cutting tool to which the diamond product according to claim 7 is attached so that a polished surface is outside.