JP3350994B2 - Manufacturing method of diamond sheet - 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 producing a diamond sheet, and more particularly to a method for producing a diamond sheet used for cutting tools, wear-resistant tools, precision tools, semiconductor materials, electronic parts, optical parts and the like.

[0002]

2. Description of the Related Art Conventionally, diamond has been used as a tool, a heat sink for semiconductors, and an optical window material in the form of a single crystal or a sintered body. It was necessary to process the diamond into a thin plate. However, diamond has the highest hardness among materials, and its processing is not easy. Conventional techniques for slicing diamond into a thin plate include a method of applying diamond powder to a circular thin metal plate and using it as a rotary blade, a method of electric discharge machining, a method of cleaving along a (111) crystal plane, and a laser beam. There is known a method of condensing light, and sublimating or burning a portion irradiated with a laser beam by applying the laser beam to a diamond to burn it off.

[0003]

In recent years, it has become possible to deposit thin plate-like diamond on a substrate at low cost by a gas phase synthesis method. However, in applications where only diamond is required, the substrate is removed. You need to take out the diamond. If a large amount of diamond thin plates are to be manufactured by the vapor phase synthesis method using this method, a large number of substrates must be prepared, which has hindered the cost reduction of diamond thin plate manufacturing.
In order to solve this problem, a method has been desired in which diamond is deposited thickly on a substrate by a vapor phase synthesis method, and the diamond deposited by some processing method is sliced thinly.

Further, the conventional methods of processing diamond into a thin plate have the following disadvantages, respectively, and are costly and time consuming. I couldn't make the most of it.

[0005] That is, the conventional method of applying diamond powder to a circular thin metal plate and using it as a rotary blade is slow in cutting diamond and is not suitable for cutting a large-area plate-shaped diamond.

Further, the electric discharge machining method can be applied only to a conductive material, and is not suitable for a method of cutting an insulating diamond used as an electronic component or the like which requires an insulating property.

The method of cleavage along the (111) crystal plane can be applied only in the direction parallel to the single crystal (111) crystal plane, and cannot be applied to polycrystalline diamond. Since the (111) plane is the hardest plane in the crystal orientation of diamond, it is difficult to perform processing such as surface polishing of the cut diamond thin plate.

Further, a method in which a laser beam is condensed and applied to diamond to burn off by sublimating or burning a portion irradiated with the laser beam is inherently transparent to light and has very high thermal conductivity. Since the diamond can be cut only at the portion that hits the focal point where the laser light is focused intensely, it is difficult to make a cut of 1 mm or more, and the deeper the cut amount, the more diamond is lost as a cut margin There was a problem that the number increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a method of manufacturing a polycrystalline or single crystal diamond thin plate which is excellent in mass productivity and inexpensive. And

[0010]

Means for Solving the Problems The present inventors have found that, when diamond is synthesized by vapor phase synthesis, diamond layers having high light transmittance and diamond layers having low light transmittance are alternately laminated. After synthesizing, laser light is injected into the diamond, and the laser light is absorbed by the diamond layer with low light transmittance. I came to.

In the method for producing a diamond thin plate according to the present invention, a first diamond layer having a high light transmittance and a second diamond layer having a light transmittance lower than that of the first diamond layer are alternately formed by a vapor phase synthesis method. Forming a diamond laminated body in which the first and second diamond layers are alternately laminated, and irradiating the diamond laminated body with laser light so that the second diamond layer is irradiated with laser light. And separating the first diamond layer as a diamond thin plate with the second diamond layer as a boundary.

Preferably, the first diamond layer has a Raman scattering ratio with respect to graphite carbon of 0.1 or less, and the second diamond layer has a Raman scattering ratio with respect to graphite carbon of 0.2 or more. is there. The first diamond layer is not particularly limited as long as the Raman scattering ratio with respect to the graphite carbon is 0.1 or less, and in practice, it can be close to 0 up to the measurement limit. . However, in consideration of the application, the production cost, and the like, the Raman scattering ratio of the first diamond layer to the graphite carbon is sufficiently 0.005 or more and 0.1 or less. The second diamond layer is not particularly limited as long as the Raman scattering ratio with respect to the graphite carbon is 0.2 or more. However, considering the quality and the like of the diamond layer grown on the second diamond layer, the second diamond layer preferably has a Raman scattering ratio of graphite carbon to 0.2 or more and 20 or less. The Raman scattering ratio of the first diamond layer to the graphite carbon and the Raman scattering ratio of the second diamond layer to the graphite carbon were 1800 cm ^{-1 to} 100 by Raman spectroscopy.
1360 cm measured from the back land between 0 cm ^-1
Maximum peak ratio of non-diamond carbon of ^{-1 ~1580cm -1} (graphite quality carbon) and (Y), the peak ratio of the peak height of the measured-diamond carbon peak periphery of 1333 cm ^-1 as Buckland (X) (Y / X). The method of calculating the Raman scattering ratio is disclosed in Japanese Patent Application Laid-Open No. H2-2232106.

Further, the second diamond layer preferably contains the concentration of impurity elements other than hydrogen at least 10 times higher than that of the first diamond layer. Note that the second diamond layer is not particularly limited as long as it contains an impurity element concentration other than hydrogen of 10 times or more as compared with the first diamond layer, but is actually 10 times or more and 1000 times or less. It is enough to include.

As the impurity element other than hydrogen contained in the second diamond layer, N or B which is easily incorporated into diamond during vapor phase synthesis is most suitable.
l, Si, P, S or other metal elements may be used. By the way, even if hydrogen is contained in diamond as an impurity, it causes light absorption only in the infrared region in the range of 2.5 μm to 10 μm, so it is difficult to use hydrogen as an impurity in the present invention. Is not considered as an impurity. However, for diamond synthesized by a gas phase synthesis method, for example, diamond having poor crystallinity or diamond having strong light absorption generally contains 0.1% of hydrogen.
It should be noted that the percentage is often higher than%.

When N is introduced into diamond, 0.5
Light absorption increases in a short wavelength region of less than μm and in a region near a wavelength of 7 μm. Therefore, when an excimer laser or a nitrogen laser having a short wavelength is used, N doping is preferable.

When B is introduced, a wavelength of 0.6
Since light absorption increases in the region of not less than μm and not more than 5 μm, Y
When an AG laser, a glass laser, or the like is used, B doping is preferable. Note that as the laser, various lasers can be used in accordance with a wavelength at which light absorption caused by an impurity element introduced into diamond increases, and a gas laser, a liquid laser, a solid-state laser, or the like can be used.

The amount of impurities to be introduced into the second diamond layer needs to be 20 ppm or more as impurities except hydrogen in order to provide sufficient light absorption.
Although there is no particular limitation, the amount of impurities is 50
00 ppm or less is sufficient. On the other hand, the first diamond layer preferably has an impurity concentration other than hydrogen of 15 ppm or less in order to transmit a laser beam having a sufficient output. Further, although not particularly limited, the amount of impurities may be contained at 0.1 ppm or more.

In order to make the cutting interface flat, the impurity concentration of the second diamond layer (light absorbing layer) and the first diamond layer (light transmitting layer) must be 10 times or more in elemental ratio. Preferably, it is the difference.

In the present invention, the difference between the second diamond layer (light absorbing layer) and the first diamond layer (light transmitting layer) in the wavelength of the laser used is five times or more the light absorption coefficient shown below. There must be.

[0020]

(Equation 1)

The present invention can be used in the production of a single-crystal diamond thin plate as well as in the production of a polycrystalline diamond thin plate. However, in the production of a single-crystal diamond thin plate, if a diamond layer having low crystallinity is sandwiched as a second diamond layer (light absorption layer) in the middle layer of the diamond laminate,
In the production of a single-crystal thin plate, it is preferable to use a method of doping impurities, since this adversely affects the subsequent growth of single-crystal diamond.

Various diamond gas phase synthesis methods can be used for the gas phase synthesis method used in the present invention. For example, such a diamond vapor phase synthesis method is not particularly limited in the following cases, but may include a plasma CVD method, a hot filament method, a flame method, and the like which have been known so far.

[0023]

According to the present invention, in the step of forming a diamond layer to a film thickness by a vapor phase synthesis method, an intermediate layer of a diamond layer in which a second diamond layer (a diamond layer having a high light absorptivity) is formed in advance. Is provided. Therefore, a laser beam is made incident through the first diamond layer (diamond layer having high light transmittance), which is the upper layer of the diamond laminate formed according to the present invention, and the laser beam is applied only to the second diamond layer (light absorption layer). By absorbing light energy, the second diamond layer (light absorbing layer)
The first diamond layer can be cut into a plurality of stages as a diamond thin plate from the diamond laminate formed to have a film thickness at the boundary of.

[0024]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Embodiment 1 FIG. 1 is a process diagram schematically showing a method for producing a diamond thin plate as one embodiment according to the present invention. With reference to FIG. 1, a method for producing a diamond thin plate will be described.

By hot filament CVD, 50 m
A polycrystalline diamond (diamond laminate) 2 was grown on a Si wafer 1 having a diameter of m. The polycrystalline diamond 2 has a structure in which first diamond layers (light transmitting layers) 3 and second diamond layers (light absorbing layers) 4 are alternately stacked. The first diamond layer (light transmitting layer) 3 is grown for 160 hours using methane diluted to 1.2% with hydrogen as a raw material, and the second diamond layer (light absorbing layer) is grown.
As 4, use methane diluted to 4% with hydrogen as a raw material
Grow for hours. In each case, the gas pressure during growth was 5
At 0 Torr, the growth temperature was 900 ° C. Under these conditions, growth was performed in the order of light absorbing layer-light transmitting layer-light absorbing layer-light transmitting layer-light absorbing layer-light transmitting layer-light absorbing layer-light transmitting layer. The thickness of each of the obtained light transmitting layers 3 was about 200 μm, and the thickness of the light absorbing layer 4 was 3 μm. The light absorption coefficient of the light absorbing layer 4 was 30 times that of the light transmitting layer 3 at a wavelength of about 10 μm.

A CO ₂ laser 5 having a wavelength of 10.6 μm and a continuous output of 30 W is applied to the polycrystalline diamond thick film 2 from above.
Is condensed by using the converging lens 6 so that the diameter becomes 2 mm on the diamond surface 2S, and the laser reflecting mirror 7 is irradiated.
Was used to scan the entire 30 mm square over about 2 seconds.
As a result, the transparent diamond layer having a thickness of 200 μm was peeled off. A light absorbing layer of about 1 μm remained on the surface of the peeled polycrystalline diamond layer on the substrate 1 side and the surface of the diamond laminate 2 on the side of the peeled polycrystalline diamond layer.
This light absorbing layer was removed by Ar ion etching. The above procedure was repeated three times to obtain three diamond thin plates.

Example 2 3 × 3 × 0.3 by microwave plasma CVD
Polycrystalline diamond (diamond laminated body) was epitaxially grown on a single-crystal diamond having a size of mm. As a light transmitting layer, growth was performed for 200 hours using methane diluted to 1.0% with hydrogen as a raw material, and 10 ppm of B ₂ was added to methane diluted to 1.2% with hydrogen as a light absorbing layer.
Using the material to which H ₆ was added as a raw material, growth was performed for 2 hours. In each case, the gas pressure during growth was 40 Torr, and the growth temperature was 860 ° C. Under these conditions, growth was performed in the order of light absorption layer-light transmission layer-light absorption layer-light transmission layer-light absorption layer-light transmission layer. The thickness of each light transmitting layer obtained is about 26
0 μm, and the thickness of the light absorbing layer was 3 μm. The concentration of B contained in the light absorbing layer was about 90 ppm as measured by secondary ion mass spectrometry, and the concentration of B contained in the light transmissive layer was about 0.2 ppm as measured by secondary ion mass spectrometry. It was 6 ppm.

The single crystal diamond epitaxial film was formed from above with Y having a wavelength of 1.06 μm and a pulse output of 0.3 J.
An AG laser was condensed and irradiated on the diamond surface so as to have a diameter of 0.2 mm, and the entire 3 mm square was scanned at 500 pulses per second. As a result, a single-crystal diamond layer having a thickness of 260 μm could be peeled off. A light absorbing layer of about 1 μm remained on the substrate side surface of the separated single crystal diamond and the surface of the diamond laminate on which the single crystal diamond layer was separated.
The absorbent layer was removed by heating to ° C.

The above procedure was repeated twice to obtain two single-crystal diamond thin plates.

Example 3 3 × 3 × 0.3 by microwave plasma CVD
A single crystal diamond (diamond laminate) was epitaxially grown on a diamond single crystal having a size of mm. As the light transmitting layer, methane diluted to 1.0% with hydrogen was used as a raw material, and growth was performed for 200 hours. As the light absorbing layer, methane diluted to 1.2% with hydrogen and 1% N ₂ was added. As a raw material, growth was performed for 2 hours. In each case, the gas pressure during growth was 60 Torr, and the growth temperature was 95.
It was 0 ° C. Under these conditions, growth was performed in the order of light absorbing layer-light transmitting layer-light absorbing layer-light transmitting layer. The thickness of each obtained light transmission layer is about 300 μm, and the thickness of the light absorption layer is 3 μm.
Met. The concentration of N contained in the light absorbing layer was about 160 ppm as measured by secondary ion mass spectrometry, and the concentration of N contained in the light transmitting layer was about 5 ppm as measured by secondary ion mass spectrometry. there were.

The single crystal diamond epitaxial film is irradiated with a XeCl excimer laser having a wavelength of 0.308 μm and a pulse output of 0.5 J from above from the top of the diamond surface so as to have a diameter of 0.3 mm at a rate of 50 pulses per second. The entire 3 mm square was scanned. As a result, the thickness is 30
The 0 μm single crystal diamond layer could be peeled off. A light absorbing layer of about 1 μm remained on the substrate side surface of the separated single crystal diamond and the surface of the diamond laminate on which the single crystal diamond layer was separated, but heated to 120 ° C. in dichromic acid. This removed this absorbent layer.

By repeating the above procedure twice, two single-crystal diamond thin plates were obtained.

[0034]

As described above, according to the present invention, a polycrystalline or single-crystal diamond thin plate can be manufactured with good mass productivity and at low cost.

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing a method for producing a diamond thin plate as one embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Polycrystalline diamond (diamond laminated body) 3 Light transmission layer (1st diamond layer) 4 Light absorption layer (2nd diamond layer) 5 Laser light 6 Condensing lens 7 Laser reflection mirror

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-141697 (JP, A) JP-A-5-13342 (JP, A) JP-A-5-24991 (JP, A) JP-A-4- 232273 (JP, A) JP-A-62-54587 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 29/04 C23C 14/06

Claims (3)

(57) [Claims] 1. A method for producing a first light-transmitting first material by a gas phase synthesis method.
And a second diamond layer having light transmittance lower than that of the first diamond layer are alternately synthesized to form a diamond stack in which the first and second diamond layers are alternately stacked. Forming a body, irradiating the diamond laminated body with laser light to cause the second diamond layer to absorb the laser light, and using the second diamond layer as a boundary to form the first diamond layer. Separating the thin diamond plate. 2. The first diamond layer has a Raman scattering ratio to graphite carbon of 0.1 or less, and the second diamond layer has a Raman scattering ratio to graphite carbon of 0.2 or more. Claim 1.
3. The method for producing a diamond thin plate according to item 1. 3. The first diamond layer according to claim 1, wherein
The method for producing a diamond thin plate according to claim 1, wherein the concentration of the impurity element other than hydrogen is 10 times or more as compared with the diamond layer of (1).