JP3387154B2 - Diamond single crystal - 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 diamond, and more particularly to a method for producing a large diamond single crystal used for semiconductor materials, electronic parts, optical parts and the like.

[0002]

2. Description of the Related Art Since diamond has many excellent properties such as high hardness, high thermal conductivity and transparency, it is widely used as a material for various tools, optical parts, semiconductors and electronic parts. For semiconductors, a diamond single crystal is required because of its optical transparency and low crystal defects. It is thought that the importance of diamond single crystals will increase in the future.

Natural diamond single crystals are classified into a type IIa type that transmits ultraviolet rays up to 230 nm and a type Ia type that hardly transmits ultraviolet rays. It is extremely difficult to obtain a single crystal having a diameter of 10 mm or more in any type. Rarely 20 in nature
Although a single crystal diamond with a diameter close to mm may be produced, it was extremely expensive and could not be used for industrial purposes. In addition, type IIa has many crystal defects and strains. For example, the half-width of the X-ray rocking curve is 500 degrees.
And the second or more also, the half-value width of the spectrum of the Raman scattered light is observed in the vicinity of 1332 cm ^-1 from such that at 2 cm ^-1 or more is considered to be unsuitable as a substrate for a semiconductor. Since the type Ia does not transmit ultraviolet rays having a wavelength of 300 nm or less, there is a problem that it cannot be used as an optical material for ultraviolet rays.

In the past, naturally occurring diamonds were used for industrial purposes, but nowadays most of them are artificially synthesized. Diamond single crystals are currently industrially synthesized under pressures in excess of tens of thousands of atmospheres, all of which are stable. An ultra-high pressure container that generates such a pressure is very expensive, the internal volume cannot be increased, and diamond cannot be inexpensively supplied. Therefore, a large single crystal cannot be synthesized. In addition, the diamond produced by the high pressure method contains nitrogen as an impurity I
Although it tends to be a crystal called b-type, this Ib-type diamond does not transmit light having a wavelength of 400 nm or less. From these facts, it has been impossible to synthesize an artificial diamond single crystal having a diameter of 10 mm or more and transmitting ultraviolet rays around 250 nm. Hitherto, relatively high-area and high-purity diamond has been artificially produced on various substrates by a vapor phase synthesis method, but these are polycrystalline films and single crystal films have not been obtained.

However, among diamond applications, it is necessary to use single crystal diamond when it is used for ultra-precision tools, optical parts, semiconductors, etc. which require a particularly smooth surface. Therefore, the conditions for epitaxial growth of a single crystal by the vapor phase synthesis method are being studied,
Furthermore, a method for producing a large-area single crystal by a vapor phase synthesis method has been studied. So far, the method of obtaining a single crystal by heteroepitaxial growth of diamond has many crystal defects and is not of sufficient quality as an optical or semiconductor substrate.

[0006]

Conventionally, it is transparent in the ultraviolet region up to 250 nm, which has a size of 15 mm or more, which is necessary for optical parts and semiconductor substrates, whether natural or artificially synthesized.
There was no diamond single crystal having a small full width at half maximum of the (400) X-ray rocking curve with few crystal defects and strain.

[0007]

[Patent Document 1] Japanese Unexamined Patent Publication No. 3-75298 discloses a method for producing a diamond single crystal by arranging a plurality of single crystal diamonds in the same orientation and growing diamond on the single crystal diamond by a vapor phase synthesis method. Is stated. When obtaining a large diamond single crystal by such a method, in order to maintain homoepitaxial growth to a predetermined thickness, the crystal orientation, intervals, and heights of a plurality of single crystal diamonds are adjusted, and the growth temperature is adjusted to an appropriate range. If it is controlled, the wavelength of 250
A large diamond single crystal with a diameter of 15 mm or more, which is transparent even in the ultraviolet region near nm and has a half width of the X-ray rocking curve within 100 seconds or a half width of the Raman scattering spectrum of 2 cm ^-1 , with good crystallinity, is used for optics. It can be supplied for semiconductors.

The present application has a maximum diameter of 15 mm or more and an ultraviolet ray transmittance of 20 at a wavelength of 250 nm.
% Or more, and the angular half width of the X-ray rocking curve on the (400) plane is 100 seconds or less, and a diamond single crystal synthesized by a vapor phase synthesis method is provided. Further, diamond single crystal obtained by the present vapor-phase synthesis method, the half-value width of the scattered radiation of the shift value 1332 cm ^-1 from the excitation light in the Raman scattering spectrum is 2 cm ^-1 or less. In addition, the term "diameter" in the present invention means the maximum length of a straight line that can be drawn in a single crystal having a certain size and shape.

[0009]

[Function] To obtain a high-quality and large-sized diamond single crystal, a method of arranging a plurality of single-crystal diamond substrates aligned in the same direction as in Japanese Patent Laid-Open No. 3-75298, and growing diamond on them by vapor phase synthesis method Is currently considered to be the best. However, in this method, when the orientations of a plurality of single crystals are deviated, a small-angle grain boundary formed between the single crystal substrates remains in the grown single crystal, causing light scattering, or between the single crystal substrates. Therefore, there is a problem that abnormally grown particles having different crystal orientations are likely to be generated. In order to avoid such a problem and grow one single crystal on a plurality of substrates, the following measures are necessary.

From the (100) plane to the growth plane of the single crystal substrate,
The surface should be within the degree. The deviation of the orientation of each single crystal substrate is suppressed within 3 degrees. The distance between adjacent single crystal substrates is 30 μm
Keep within. The growth temperature is set to a high temperature of 1000 ° C. or higher.
It is a contrivance such as aligning the height of the single crystal substrate to each other. A typical manufacturing process for achieving these conditions is to accurately measure the main surface from the artificial diamond single crystal material of high pressure synthesis in which the crystal orientation is strictly measured by means such as X-ray diffraction (10
Square, rectangular, triangular, and hexagonal diamond single crystals cut out so that the surface is within 3 degrees from the 0) surface are used as base materials, and these base materials are densely arranged and fixed in a required number. At this time, it is confirmed that there is no deviation of the crystal orientation of the substrate by 3 degrees or more, which is caused by means such as X-ray diffraction and electron beam diffraction. If there is a deviation of 3 degrees or more, the board is rotated in a direction in which the deviation is reduced, or another board is replaced, and the deviation is repeated within 3 degrees . The main surface of these substrates for growing diamond is Rmax.
It must be polished to a roughness within 0.5 μm. Further, it is preferable to similarly polish the side surfaces where the substrates are in contact with each other so that the gap between the substrates is within 30 μm. Since the edges and corners of the substrate are likely to be chipped, it is effective to chamfer within 20 μm. In order to keep the difference in height between adjacent substrates within 30 μm, it is most effective to polish the growth surface after fixing all the substrates. To suppress abnormal growth, 1000 ° C during vapor phase growth of diamond
It is preferable to grow at the above substrate temperature.

By appropriately realizing these conditions, a large single crystal of good quality can be grown on a plurality of single crystal substrates together. In the large-area single crystal thus grown, a small tilt grain boundary may exist due to a slight misorientation between the substrate single crystals, but the above-mentioned measures were taken in growing the crystal. If something
. Doing so may defect the light is scattered by the small-angle grain boundaries does not cause a problem such as a large amount occurs, the maximum distance across the diameter is 1
It has a transmittance of 5 mm or more and an ultraviolet ray at a wavelength of 250 nm of 20% or more, an angular half width of the X-ray rocking curve on the (400) plane of 100 seconds or less, and a half width of Raman scattering spectrum of 2 cm ^−1. It is possible to synthesize large-scale, high-quality diamond single crystals that have never existed naturally or artificially.

The vapor phase synthesis method for growing a diamond single crystal of the present invention includes a hot filament CVD method and a plasma CV method.
Any method such as D method, plasma jet method, combustion flame method and laser CVD method may be used. The raw material may be a substance containing carbon such as hydrocarbon and the raw material may be of any kind. The substrate used for growing the diamond single crystal of the present invention is the easiest to obtain an artificial diamond single crystal with high quality synthesized by high pressure synthesis, but natural single crystal or vapor phase grown single crystal is used as the substrate. It can also be used.

[0013]

Example: Size 4.0 mm × 4.0 mm × 300 ± 2
25 diamond 0μm {100} substrates with 1 spacing
It was arranged in 5 rows and 5 columns so that the distance was within 5 μm. Diamond was grown on the substrate thus arranged by the microwave plasma CVD method. Methane concentration 3%, pressure 1
After growing for 100 hours in total at a substrate temperature of 950 ° C. at 00 Torr to form a diamond having a thickness of 200 μm on 25 substrates, both surfaces were mechanically polished and washed with dichromic acid. At this stage, when the misalignment of the orientation of the 25 diamond single crystal substrates was examined by the X-ray diffraction method, the misorientation angle was 1.5 degrees at the maximum.

Next, on the side opposite to the side where the diamond was first grown, the methane concentration was 2%, the pressure was 120 Torr, and the substrate temperature was 1000.
℃, diborane (B ₂ H ₆ ) was added at 10ppm, B-doped semiconductor single crystal diamond in 300 hours in 150 hours
μm growth, then methane concentration 2%, pressure 120
Torr, substrate temperature 1100 ° C., high-purity diamond 700 μm not doped with 0.3% H ₂ O was grown, and B-doped layers and high-purity layers were alternately grown for a total of 3 cycles. From the diamond thus obtained, three high-purity diamond single crystal plates were cut along the B-doped layer by electric discharge machining. These both surfaces were mirror-polished, and the inferior quality of the outer edge was removed by laser processing to obtain a colorless and transparent diamond single crystal of about 20 mm square and a thickness of 500 to 600 μm. I am 27
It was mm.

When the optical transmittances of these crystals in the visible and ultraviolet regions were measured, the ultraviolet absorption edge was 225 nm over the entire surface and the transmittance at 250 nm was at least 45%. Also, three combinations of two crystals were selected from each of the three crystals obtained, and the two-crystal method X-ray rocking curve of the (400) plane by CuKα1 X-rays was measured. It was 41 seconds. When excited with an argon ion laser having a wavelength of 514.5 nm, the half-value width of the Raman scattering spectrum, which is shifted to a position of 1332 cm ⁻¹ from the excitation light and appears, has a resolution of 0.
It was 1.7 cm ^{-1 as} measured by a 7 cm ^-1 spectroscope.

[0016]

[Comparative Example] Natural diamond single crystal IIa type 2 pieces, Ia
The characteristics of three types of diamond, four high-pressure synthesized Ib type single crystals, and two high-pressure synthesized IIa type single crystals were evaluated and examined in the same manner as the three diamond single crystals of the examples of the present invention. It became so. The light transmission characteristics were measured by mirror-polishing the light input / output surface. When measuring the X-ray rocking curve by the two-crystal method, the same high-pressure synthetic Ib type diamond single crystal was used as the first crystal. From this measurement result, it was found that the diamond of the present invention is a large-sized and high-quality diamond that has never been obtained.

In Table 1, the diameter is the maximum measuring length (mm). The thickness is the optical path length (mm) in the diamond in the light transmission measurement. The absorption edge is the transmission limit wavelength (nm) in the visible to ultraviolet range. The transmittance is the transmittance at 250 nm (up to 72% from the refractive index of diamond). The X-ray half-width is the angular half-width (second) of the X-ray rocking curve measured by the above method. Raman FWHM was measured by the method described above 13
Half-width of the scattering peak in the vicinity 32cm ^-1 (cm ^-1).

[0018]

[Table 1]

[0019]

As described above, according to the present invention, a homogeneous, large-sized and large-area high-pressure phase single crystal can be used as an optical or semiconductor substrate. In the present invention, since the growth of the high-pressure phase substance is carried out by the vapor phase synthesis method, it is possible to carry out various dopings such as making diamond easily contain boron or nitrogen. Therefore, the diamond single crystal of the present invention is a precision tool cutting edge, a wear resistant tool, a heat resistant tool, a semiconductor substrate, a heat dissipation substrate,
It can be widely used for high-voltage phase semiconductor materials, optical materials, acoustic diaphragms and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-75298 (JP, A) JP-A-6-227895 (JP, A) JP-A-6-87691 (JP, A) JP-A-6- 1695 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C30B 29/04 C30B 25/02 C30B 25/18

Claims (4)

(57) [Claims] 1. A growth plane within 3 degrees of the (100) plane.
Using multiple diamond single crystal substrates
The distance between the single crystal substrates should be within 30 μm, and
The height difference between the single crystal substrates that meet each other is within 30 μm.
And was synthesized by a gas phase synthesis method at a temperature of 1000 ° C. or higher.
It is a diamond single crystal with a maximum diameter of 15
in mm or more and is the transmittance of the ultraviolet at a wavelength of 250nm is 20% or more and (400) to holder Iyamondo single crystal and wherein the angular half width of the X-ray rocking curve is not more than 100 seconds in surface. 2. A growth plane within 3 degrees of the (100) plane.
Using multiple diamond single crystal substrates
The distance between the single crystal substrates should be within 30 μm, and
The height difference between the single crystal substrates that meet each other is within 30 μm.
And was synthesized by a gas phase synthesis method at a temperature of 1000 ° C. or higher.
It is a diamond single crystal with a maximum diameter of 15
and wherein the at mm or more and is the transmittance of the ultraviolet at a wavelength of 250nm is 20% or more, and the half width of the scattered radiation of the shift value 1332 cm ^-1 from the excitation light in the Raman scattering spectrum is ^{2 cm -1} or less to folder hate <br/> Monde single crystal. 3. A diamond of the diamond single crystal substrate
Roughness of the surface on which the band is grown and the side surface is 0.5μ
It is below m, It is described in Claim 1 or 2 characterized by the above-mentioned.
Mounted diamond single crystal. 4. The corner portion of the diamond single crystal substrate is 2
Contract characterized by chamfering of 0 μm or less
The diamond single crystal according to claim 1 or 2.