JPH0740336A - Diamond machining method - Google Patents

Abstract

PURPOSE:To provide a diamond machining method for eliminating adhesion of a graphite or an amorphous carbon derived from a carbon or the like re moved by machining without any effect on a diamond body, machining a dia mond at a high speed at a high accuracy, and forming a smoothly machined surface. CONSTITUTION:A diamond 1 is machined by irradiating the diamond 1 with a light of a 190-360nm wavelength, such as a laser beam 10, in a plasma 8 of an atmospheric gas, such as an oxygen, hydrogen, or inactive gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond processing method in which diamond is irradiated with light to perform cutting or surface grinding.

[0002]

2. Description of the Related Art Diamond has many excellent characteristics such as the highest hardness and the highest thermal conductivity among all materials. Utilizing these characteristics, various kinds of heat sinks and cutting tools for semiconductor devices can be utilized. Widely used as tools. When using diamond for these purposes,
Although it is necessary to process into a predetermined shape and surface condition, diamond is the most hard of all substances, so processing is extremely difficult.

Conventionally, with respect to the processing of single crystal diamond, it has been known to some extent the direction and direction of the surface that are relatively easy to process, and within the limited range, grinding is performed by skiff polishing. However, in the case of polycrystalline diamond, the surface orientation of diamond particles is in all directions, so it was difficult to smooth the surface even by skiving. In addition, since vapor-phase synthetic diamond is apt to warp, and large-area ones may have warpage of several tens of μm, cracks may occur due to mechanical pressure during polishing in mechanical polishing such as Skaif polishing. Sometimes it was impossible to polish.

In addition, the processing speed of skiff polishing is 1 μm.
There was a drawback that the processing efficiency was extremely low and the processing efficiency was extremely poor. Further, in the skiff polishing, there is a difficulty in the method of fixing the sample. Therefore, when the shape is too small or the shape is irregular, the workability is poor and sometimes the processing is impossible.

On the other hand, with respect to the cutting process of diamond, in the case of a diamond sintered body sintered by using a conductive sintering aid, it was possible to cut by electric discharge machining. However, electric discharge machining cannot be used for a diamond sintered body using a non-conductive sintering aid, and diamond having no electric conductivity such as single crystal diamond and vapor phase synthetic diamond. Therefore, cutting with a laser is considered, and cutting with a CO ₂ laser, a CO laser, or a YAG laser has been conventionally performed.

However, these lasers have a wavelength of 1 μm.
Since the above infrared rays are used to heat and melt the diamond for processing, there is a drawback that the diamond around the processed portion is deteriorated by heat. In addition, carbon removed by heating and melting of diamond is deposited as graphite or amorphous carbon near the processed surface, or amorphous carbon such as soot generated by decomposition of CO ₂ in the atmosphere by irradiation of laser light is generated. There was a defect that it adhered to the diamond surface.

[0007] Graphite and amorphous carbon adhered and deposited near the processed surface of diamond absorb the irradiated laser light, so that the energy efficiency is lowered and the processing speed becomes very slow, and further the shape of the processed surface is changed. Affects the deterioration of processing accuracy and reduces the smoothness of the processed surface. Also, in order to remove the attached graphite and amorphous carbon, mechanical grinding, evaporation by laser or etching treatment with acid etc. is required after processing, or finish by mechanical polishing for the purpose of improving the lowered accuracy and smoothness. Processing was required.

[0008]

In view of the above conventional circumstances, the present invention is a method of processing a diamond by irradiating light with the carbon of diamond removed by the processing without any influence on the diamond body. Eliminates the adhesion of graphite and amorphous carbon derived from
An object of the present invention is to provide a diamond processing method capable of processing diamond at high speed with high accuracy and obtaining a smooth processed surface.

[0009]

In order to achieve the above object, the method for processing diamond provided by the present invention is a method for processing diamond by irradiating it with light, wherein the diamond has a wavelength of 190 in plasma of atmospheric gas. ~ 36
It is characterized in that light of 0 nm is irradiated.

[0010]

The present inventors have found that by irradiating light (ultraviolet light) having a wavelength of 190 to 360 nm, the carbon-carbon bond constituting diamond is affected and the diamond is decomposed. Based on this knowledge, we propose a new method for processing diamond. That is, by collecting light of the above wavelength and irradiating it with light of high energy density, multiphoton absorption occurs and most of the incident light is absorbed by the diamond surface, which does not damage the diamond at all, Good processing can be done.

The reason why diamond can be processed with light of the above wavelength is considered to be as follows. That is,
The absorption of light by diamond has the absorption curve shown in FIG. 1 in the case of high-purity type IIa single crystal diamond. Figure 1
As can be seen from the above, the absorption of light by diamond gradually increases as the wavelength becomes shorter in the wavelength range of 400 nm to 240 nm, and sharply increases near 220 nm to be completely absorbed.

Light in this region is ultraviolet light, and it is known that when it is absorbed by a substance, it mainly excites electrons of a chemical bond. Especially for diamond, the wavelength is 19
The light in the range of 0 to 360 nm has a great influence on the carbon-carbon bond, and it does not penetrate to the inside and is almost 10 in the surface layer.
Since it is absorbed by 0%, the diamond is decomposed only in the surface portion irradiated with light, which enables high-speed and efficient processing.

However, when the diamond is processed by irradiating it with light in the above wavelength range, carbon removed from the diamond is near graphite or amorphous carbon near the processed surface, as in the case of the conventional infrared laser processing. It is unavoidable that amorphous carbon such as soot, which is formed as a soot or is generated by the decomposition of CO ₂ in the atmosphere by irradiation of light, is attached to the diamond surface. As a result, inconveniences such as a decrease in light energy efficiency and a decrease in processing speed, deterioration of processing accuracy, and a decrease in smoothness of a processed surface were recognized.

In order to eliminate the inconvenience caused by the deposition and deposition of graphite and amorphous carbon, as a result of intensive research, it was removed from diamond by irradiating and processing light having a wavelength of 190 to 360 nm in plasma of atmospheric gas. It has been found that it is possible to extend the flight path of the material and prevent it from adhering to the periphery of the machined surface. Moreover, it was also confirmed that if a highly reactive plasma is used, an etching phenomenon occurs due to the plasma on the surface of the diamond, so that higher speed processing becomes possible.

Specifically, when plasma of hydrogen or an inert gas is used, graphite and amorphous carbon are rapidly etched by these plasmas and removed without adhering to the diamond surface. On the other hand, since the etching rate of diamond by the plasma is extremely low, the processing of diamond proceeds mainly by the reaction with the irradiated light, resulting in a very smooth processed surface. The inert gas has a wavelength of 190 to 360.
He, Ne, Ar, K which has no absorption edge in the ultraviolet region of nm
Inert gases such as r and Xe, among which Ar or He is preferable.

On the other hand, when oxygen plasma is used, this plasma etches not only graphite and amorphous carbon but also diamond at a high speed. Therefore, when the diamond is processed by the irradiation of light in oxygen plasma, the adhesion of graphite and amorphous carbon is prevented, and at the same time, the diamond is etched by the oxygen plasma in addition to the processing by the reaction with the irradiated light. It enables machining at a much higher speed than machining in other atmospheres.

However, since the etching rate of diamond by oxygen plasma sensitively depends on the concentration distribution of oxygen plasma, the processed surface is likely to be rough due to variations in the etching rate, and the obtained processed surface is a plasma of hydrogen or an inert gas. Inferior in smoothness to the case of.

In order to prevent roughening of the machined surface due to oxygen plasma, oxygen is mixed with an inert gas to generate plasma,
It is effective to perform processing in the plasma of this mixed gas, and a processed surface having high smoothness can be obtained at a high processing speed. In this case, the processing speed and the smoothness of the processed surface depend on the oxygen concentration in the mixed gas. The higher the oxygen concentration, the faster the processing speed, but the smoothness of the processed surface decreases. To obtain the desired surface smoothness, the oxygen concentration should be 20% by volume.
The following is preferable.

Any light source may be used as long as it can emit light in the ultraviolet region having a wavelength of 190 to 360 nm. For example, ArF and Kr.
A laser such as an excimer laser having a specific oscillation wavelength such as Cl, KrF, XeCl, N ₂ or XeF, or a mercury lamp having a continuous wavelength band including the above-mentioned ultraviolet region can be used. In the case of a light source having a continuous wavelength band such as a mercury lamp, light in the continuous wavelength band may be used as it is, but it is preferable to narrow the wavelength band with an optical filter or the like. Since the ArF excimer laser may be attenuated in energy by absorbing oxygen, it is desirable to avoid using it in a plasma containing oxygen.

The energy density of the irradiation light is preferably in the range of 10 to 10 ¹¹ W / cm ² because if the energy density is too low, the diamond will not be decomposed, and if it is too ^high , the areas other than the processed surface will be deteriorated. 1 when using pulsed laser light
Energy density per pulse is 10 ^-1 to 10 ⁶ J /
A range of cm ² is preferred. Within the above range, the higher the energy density, the higher the processing speed, so
It is preferable to use a device capable of generating high energy. Further, when using pulsed laser light, the processing speed increases in proportion to the pulse repetition frequency, so it is preferable to use a highly repetitive laser oscillator as the device.

The laser beam has a non-uniform energy distribution in the beam, and this can generally cause the smoothness and accuracy of the machined surface to deteriorate. There are also commercially available beam homogenizers that evenly correct the energy distribution,
These devices have a drawback that the energy efficiency is lowered because the beam energy is attenuated by about 60%. However, in the diamond processing method of the present invention, if the laser light is linearly focused and irradiated by the cylindrical lens or the cylindrical mirror, the energy distribution in the beam can be obtained without particularly homogenizing the energy. A smooth machined surface can be obtained regardless of.

When the laser light is condensed by the cylindrical lens or the cylindrical mirror, the converging property of the lens can be improved by reducing the spread angle of the laser light oscillated from the laser oscillator to 5 × 10 ^-1 mrad or less. Since it can be increased, it is advantageous in terms of sharpness and smoothness of the processed surface. When more precise processing is required, it is effective to narrow the wavelength band. In that case, it is preferable to set the half bandwidth of the wavelength band within the range of 10 ^-4 to 10 ^-1 nm. As a method for narrowing the band, there are a method using an etalon and an injection lock method.

[0023]

Example 1 A diamond film formed on a substrate by a vapor phase synthesis method
It processed by irradiating an excimer laser in hydrogen plasma by the apparatus shown in FIG. 2 and FIG. That is, a plate-shaped diamond 1 having a surface roughness Ra of 3 μm, a size of 10 mm square and a thickness of 350 μm is held on a support 2 and supported in a quartz tube 3 serving as a reaction chamber. Hydrogen gas was supplied into the chamber 3.

Next, the plasma generator shown in FIG. 2 oscillates a microwave of 2450 MHz from the magnetron 4, and a resonator 6 provided with the quartz tube 3 sandwiched through the waveguide 5.
The plasma of hydrogen 8 on the surface of the diamond 1 in the quartz tube 3 while controlling the generation of the standing wave by the plunger 7.
Was generated. At this time, the pressure in the quartz tube 3 is 50 Tor.
The output of r and the microwave was set to 500W.

In this state, the laser light irradiation device of FIG. 3 is used to oscillate the laser light 10 of the KrF excimer laser having the oscillation wavelength of 248 nm from the laser oscillator 9, and the laser light 10 is focused by the mask 11. A reflection mirror 12 made of a dielectric multi-layer mirror and a cylindrical lens 13 made of a synthetic quartz convex lens for a length of 10
The quartz window 1 of the quartz tube 3 collects light in a linear shape with a width of 100 μm.
The surface of the diamond 1 was irradiated in a plasma 8 of hydrogen through the sample 4. The energy density of the irradiated laser beam 10 was 7 J / cm ² , and the repetition of pulses was 100 Hz.

The laser beam 10 scans the surface of the diamond 1 four times at a speed of 1 mm / min by moving the angle of the reflection mirror 12 and the position of the cylindrical lens 13 in association with each other in the direction of the arrow in FIG. Let That is, length 1
The surface of the diamond 1 is scanned by scanning 4 times in the right-angle direction at a speed of 1 mm / min while processing the 10 mm left-right length direction of the diamond 1 with the laser beam 10 focused in a linear shape of 0 mm width 100 μm. Removed.

After processing, the thickness of the diamond 1 was measured and found to be 200 μm, and its surface roughness Ra was smoothed to 0.1 μm. Further, the processed surface of the obtained diamond 1 can be subjected to Raman spectroscopic analysis without finishing polishing or surface treatment, and a sharp peak peculiar to diamond is observed at 1333 cm ^-1 by observation of the spectrum by Raman scattering. Was given.

Example 2 A diamond film formed on a substrate by a vapor phase synthesis method
Using the same apparatus as in Example 1, processing was performed by irradiating an excimer laser in oxygen plasma. That is, a plate-like diamond having a surface roughness Ra of 5 μm, a size of 25 mm square and a thickness of 500 μm is supported in a quartz tube, and a microwave is introduced into oxygen gas supplied into the quartz tube to generate oxygen plasma. Was generated. At this time, the pressure in the quartz tube was 50 Torr, and the microwave output was 500 W.

As the excimer laser, a XeCl excimer laser having an oscillation wavelength of 308 nm was used, and the laser light was 25 mm in length and 100 in width as in Example 1.
It was condensed in a linear shape of μm, guided into a quartz tube, and irradiated on the surface of diamond in oxygen plasma. The energy density of the irradiated laser light was 7 J / cm ² , and the pulse repetition was 100 Hz. The laser light is moved by moving the angle of the reflection mirror and the position of the cylindrical lens in conjunction with each other, so that the surface of the diamond is 2 mm.
It was scanned 4 times at a speed of / min.

After processing, the thickness of the diamond was measured and found to be 280 μm, and its surface roughness Ra was 0.1.
It was smoothed to 3 μm. The processed surface of the obtained diamond can be subjected to Raman spectroscopic analysis without finishing polishing or surface treatment, and a sharp peak peculiar to diamond is observed at 1333 cm ^-1 by observation of the spectrum by Raman scattering. It was

For comparison, a plate-shaped diamond having a surface roughness Ra of 4 μm, a size of 25 mm square and a thickness of 350 μm was processed by irradiating XeCl excimer laser while blowing oxygen gas. The laser light was focused using the same mask, reflecting mirror, and cylindrical lens as in the apparatus of FIG. 3, and was scanned four times at a speed of 2 mm / min as in Example 1. Energy density of laser light is 10 J / cm
² and repetition of pulse were 100 Hz. The processed diamond has a thickness of 200 μm and its surface roughness Ra.
Was 0.5 μm.

Example 3 A diamond film formed on a substrate by a vapor phase synthesis method
Processing was performed by irradiating an excimer laser in Ar plasma using the same apparatus as in Example 1. That is, a plate-like diamond having a surface roughness Ra of 2.7 μm, a size of 25 mm square and a thickness of 350 μm is supported in a quartz tube, and microwaves are introduced into Ar gas supplied into the quartz tube to introduce Ar gas. Generated plasma. At this time, the pressure in the quartz tube is 50 Torr, and the microwave output is 500 W.
And

An ArF excimer laser having an oscillation wavelength of 193 nm is used as the excimer laser, and this laser light is 25 mm long and 100 μm wide in the same manner as in Example 1.
The light was condensed in a linear shape of m, led into a quartz tube, and irradiated on the surface of the diamond in Ar plasma. The energy density of the irradiated laser light was 10 J / cm ² , and the repetition of pulses was 100 Hz. The laser light is moved by moving the angle of the reflection mirror and the position of the cylindrical lens in conjunction with each other, so that the surface of the diamond is 2 mm.
It was scanned 4 times at a speed of / min.

After processing, the thickness of the diamond was measured and found to be 200 μm, and the surface roughness Ra was 0.1.
It was smoothed to 1 μm. The processed surface of the obtained diamond can be subjected to Raman spectroscopic analysis without finishing polishing or surface treatment, and a sharp peak peculiar to diamond is observed at 1333 cm ^-1 by observation of the spectrum by Raman scattering. It was

Example 4 A diamond film formed on a substrate by a vapor phase synthesis method
Using the same apparatus as in Example 1, processing was performed by irradiating an excimer laser in plasma of a mixed gas of Ar and 5% by volume of oxygen. That is, a plate-like diamond having a surface roughness Ra of 3 μm, a size of 10 mm square and a thickness of 400 μm is supported in a quartz tube, and microwaves are introduced into a mixed gas supplied into the quartz tube to introduce Ar and oxygen. Mixed gas plasma was generated. At this time, the pressure in the quartz tube is 50T
The output of orr and microwave was set to 500W.

As the excimer laser, a XeCl excimer laser having an oscillation wavelength of 308 nm was used. This laser light was used in the same manner as in Example 1 to have a length of 10 mm and a width of 10
The light was focused into a 0 μm linear shape, guided into a quartz tube, and irradiated on the surface of the diamond in a mixed gas plasma of Ar and oxygen.
The energy density of the irradiated laser light is 20 J / c
The repetition rate of m ² and the pulse was 100 Hz. By moving the angle of the reflection mirror and the position of the cylindrical lens in conjunction with the laser light, the surface of the diamond was scanned four times at a speed of 2 mm / minute as in Example 1.

After processing, the thickness of the diamond was measured and found to be 200 μm, and the surface roughness Ra was 0.1.
It was smoothed to 2 μm. The processed surface of the obtained diamond can be subjected to Raman spectroscopic analysis without finishing polishing or surface treatment, and a sharp peak peculiar to diamond is observed at 1333 cm ^-1 by observation of the spectrum by Raman scattering. It was

Example 5 Single crystal Ib type diamond was cut by irradiating an excimer laser in a mixed gas plasma of Ar and oxygen using the same apparatus as in Example 1. That is, a single crystal Ib type diamond having a size of 5 mm square and a thickness of 1 mm is supported in a quartz tube, a mixed gas of Ar and oxygen is supplied into the quartz tube at a pressure of 50 Torr, and a microwave having an output of 500 W is introduced. To generate plasma.

An ArF excimer laser having an oscillation wavelength of 193 nm was used as the excimer laser, and an unstable resonator and an injection lock mechanism were provided to enhance the parallelism of the laser light and narrow the oscillation wavelength band. This laser beam was used in the same manner as in Example 1 to have a length of 5 mm.
Then, the light was condensed into a linear shape having a width of 10 μm, guided into a quartz tube, and irradiated on the surface of the diamond in a mixed gas plasma of Ar and oxygen. The energy density of the irradiated laser light is 100J
/ Cm ² , and repetition of pulse was 100 Hz.

In this way, the above single crystal Ib type diamond could be cut by irradiating the laser beam in parallel with the normal line direction of the diamond surface for about 150 seconds. The obtained cut surface was very smooth, and the surface roughness Ra was 0.2 μm.

[0041]

According to the present invention, in the method of processing a diamond by irradiating with light, the diamond is not affected at all and the adhesion of graphite or amorphous carbon to the diamond is prevented, The cutting and grinding of the surface can be performed at high speed,
It is possible to obtain a processed surface that is smoothed with high accuracy.

Therefore, the diamond processing method of the present invention is extremely useful in fields where the processing was conventionally difficult or the processing cost was very high because of the high hardness and relatively weak oxidation resistance of diamond. Is.

[Brief description of drawings]

FIG. 1 is an absorption curve of type IIa single crystal diamond.

FIG. 2 is a schematic side view showing a part including a plasma generator, which is a specific example of the apparatus for carrying out the method of the present invention.

FIG. 3 is a schematic side view showing a part including a laser light irradiation device, which is a specific example of the device for carrying out the method of the present invention.

[Explanation of symbols]

 1 Diamond 2 Support 3 Quartz Tube 4 Magnetron 5 Waveguide 6 Resonator 7 Plunger 8 Plasma 9 Laser Oscillator 10 Laser Light 11 Mask 12 Reflection Mirror 13 Cylindrical Lens 14 Quartz Window

Claims (4)

[Claims] 1. A method of processing a diamond by irradiating light with light, wherein the diamond is irradiated with light having a wavelength of 190 to 360 nm in plasma of an atmospheric gas. 2. The diamond processing method according to claim 1, wherein light is irradiated in a plasma of hydrogen or an inert gas to obtain a smooth processed surface. 3. The diamond processing method according to claim 1, wherein the diamond is processed at a high speed by irradiating light in oxygen plasma. 4. The diamond processing method according to claim 1, wherein light is irradiated in the plasma of a mixed gas of an inert gas and 20% by volume or less of oxygen gas.