JP2012131707A - Single crystal diamond, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably provide a high-quality single crystal diamond useful as a substrate for a semiconductor device, and having a large area and little strain.SOLUTION: The single crystal diamond is grown by a vapor phase synthesis method, wherein the retardation between two mutually orthogonal linearly polarized lights outgoing from a principal surface being the opposite surface by irradiation of a linearly polarized light regarded as the synthesis of two mutually orthogonal linearly polarized lights on the other principal surface is a maximum of ≤50 nm per 100 μm of a sample thickness across the whole sample.

Description

  The present invention provides a large diamond single crystal suitable for diamond, particularly a substrate for semiconductor devices and optical components, and a method for producing the same.

  Since diamond has many excellent properties such as high hardness, high thermal conductivity, high light transmittance, wide band gap, etc., it is widely used as a material for various tools, optical parts, semiconductors, electronic parts, In the future, it will be even more important. In the past, naturally occurring diamonds have been used for industrial applications, but now industrial applications are mainly artificially synthesized. Diamond single crystals are currently synthesized industrially under pressures of tens of thousands of atmospheres or more. Such an ultra-high pressure vessel that generates a high pressure is very expensive and has a limited size. Therefore, there is a limit to the synthesis of a large single crystal by a high-temperature and high-pressure method. As for the Ib type diamond having a yellow color containing nitrogen (N) as an impurity, a 1 cmφ class diamond is synthesized and sold by a high pressure synthesis method, but this size is considered to be almost limit. Further, the colorless and transparent type IIa diamond having no impurities is limited to a smaller one of several mmΦ or less except for natural ones.

  On the other hand, a gas phase synthesis method is established as a diamond synthesis method along with a high pressure synthesis method. According to this method, a relatively large area of several centimeters to 10 centimeters is artificially manufactured, but these are usually polycrystalline films. However, it is necessary to use single crystal diamond when used for ultra-precision tools, optical parts, semiconductors, etc. that require a smooth surface, among diamond applications. Therefore, methods for obtaining single crystal diamond by epitaxial growth by vapor phase synthesis have been studied.

  In general, the epitaxial growth is considered to be homoepitaxial growth in which a growing material is grown on the same type of substrate and heteroepitaxial growth in which a growth material is grown on a different type of substrate. In heteroepitaxial growth, cubic boron nitride (cBN), silicon carbide, silicon, nickel, cobalt, and the like have been reported so far (see Patent Document 1, Patent Document 2, and Patent Document 3), but the film quality is improved by heteroepitaxial growth. Since no single crystal has been obtained, single crystal synthesis by homoepitaxial growth is considered to be promising. In homoepitaxial growth, a large IIa single crystal diamond that exceeds the IIa diamond obtained at high pressure can be obtained by epitaxially growing high-purity diamond on the diamond Ib substrate by high-pressure synthesis from the vapor phase. It has also been reported that a diamond having only a low-angle grain boundary can be obtained by using a plurality of diamond substrates or diamond grains oriented in the same crystal orientation and growing a single diamond thereon (patent) Reference 4).

JP-A-63-224225 JP-A-2-233591 JP-A-4-132687 Japanese Patent Laid-Open No. 3-75298

  When single crystal diamond obtained by these methods is used as a substrate for a semiconductor device, it is required to have a large area, low distortion, and low cost. The inventors have a half-width of the X-ray rocking curve on the (400) plane of 10 to 80 seconds, and have excellent characteristics as a substrate for a semiconductor device, and a low-cost diamond single crystal can be obtained. However, we have been continually developing for further quality improvement and cost reduction.

Therefore, as a result of intensive studies, the present inventors have determined that in an evaluation method using birefringent light, a phase difference generated when linearly polarized light orthogonal to each other passes through a sample is within a certain range. The present invention was completed by finding that it does not greatly affect the characteristics as a semiconductor substrate.
The present invention is as described below.

(1) The phase difference between two mutually orthogonal linearly polarized lights emitted from the principal surface opposite to each other is irradiated with linearly polarized light that is regarded as a combination of two mutually orthogonally linearly polarized lights from one main surface, A single crystal diamond grown by a vapor phase synthesis method having a maximum thickness of 50 nm or less per 100 μm thickness.
(2) The single crystal diamond according to (1), wherein the diamond has a thickness of 100 μm or more and 1500 μm or less.
(3) The single crystal diamond according to (1), wherein the resistivity at room temperature is 10 ¹² Ωcm or more.
(4) The spin density obtained by electron spin resonance is 1 × 10 ¹⁷ / cm ³ or less at room temperature in the range where the g value is 2.0020 or more and less than 2.0028, according to (1) Single crystal diamond.
(5) The single crystal diamond according to (1), wherein the concentration of nitrogen atoms as impurities is 0.01 ppm to 100 ppm.
(6) The single crystal diamond according to (1), wherein the concentration of silicon atoms as impurities is 0.01 ppm to 1000 ppm.
(7) The single crystal diamond according to (1), wherein the main surface and side surfaces are substantially (100) planes.
(8) a step of etching and removing one principal surface of a single crystal diamond substrate to be a seed by reactive ion etching, and then newly growing a single crystal diamond layer by a vapor phase synthesis method;
Including a step of separating a single crystal diamond substrate to be a seed and a single crystal diamond layer newly grown by a vapor phase synthesis method,
A method for producing single crystal diamond, wherein the single crystal diamond substrate as the seed is grown by a high pressure synthesis method or a vapor phase synthesis method.
(9) The method for producing a single crystal diamond according to (8), further comprising a step of mechanically polishing a side surface of the single crystal diamond substrate serving as the seed before the step of growing the single crystal diamond layer. Method.
(10) The single crystal according to (9), wherein the mechanical polishing step causes the inclination of the side surface of the single crystal diamond substrate to be in the range of 82 degrees to 98 degrees with respect to the main surface. Diamond manufacturing method.
(11) A step of etching and removing the side surface by reactive ion etching after the step of mechanically polishing the side surface of the single crystal diamond substrate as the seed and before the step of growing the single crystal diamond layer. The method for producing a single crystal diamond according to (9) or (10), characterized by comprising:
(12) In the step of etching and removing one main surface and / or side surface of the single crystal diamond substrate as the seed by reactive ion etching, the thickness removed by etching is 0.5 μm or more and less than 400 μm. The method for producing single crystal diamond according to (8) or (11).

  By using the diamond and the manufacturing method thereof according to the present invention, it is possible to apply a diamond single crystal to a semiconductor device substrate. Furthermore, it opens up new avenues for optical component applications that require low distortion.

In the evaluation method using birefringent light, the inventors of the present invention have a large characteristic in the characteristics as a semiconductor substrate if the phase difference generated when the mutually orthogonal linearly polarized light passes through the sample is within a certain range. Found no effect. The range is a phase difference of 50 nm or less per 100 μm thickness over the entire sample. And if it is preferably 10 nm or less, particularly preferably 3 nm or less, it can be used for optical parts such as ultraviolet optical applications.
Such a diamond has a thickness of 100 μm or more and 1500 μm or less, a diameter of 4 mm or more, a resistivity at room temperature of 10 ¹² Ωcm or more, and a spin density obtained by electron spin resonance. In the range where the g value is 2.0020 or more and less than 2.0028, it is 1 × 10 ¹⁷ / cm ³ or less, the concentration of nitrogen atoms as impurities is 0.01 ppm to 100 ppm, silicon as impurities An atomic concentration of 0.01 ppm to 1000 ppm is suitable for use as a semiconductor device substrate. Here, the room temperature is 20 ° C. ± 15 ° C.

  Such a diamond substrate includes a step of preparing a single crystal diamond substrate as a seed, and one main surface thereof is removed by reactive ion etching (hereinafter referred to as RIE), and then the main surface is removed. The method includes a step of newly growing a single crystal diamond layer by a vapor phase synthesis method, and a step of separating a single crystal diamond substrate to be a seed from a single crystal diamond layer newly grown by a vapor phase synthesis method. It was found to be obtained by the manufacturing method. Further, it has been found that the polycrystalline silicon substrate can be obtained by a manufacturing method including a step of mechanically polishing a side surface of a single crystal diamond substrate to be a seed before the polycrystalline growth and then etching away the main surface and / or the side surface.

  As described above, even when the rocking curve of the (400) plane is in the range of 10 to 80 seconds, various characteristics (insulation resistance, mobility, etc.) for semiconductor devices vary. As a cause of this, the inventors have made extensive studies from various angles, paying attention to crystal distortion. As a result, in the evaluation method using birefringent light, if linearly polarized light that is orthogonal to each other passes through the sample and the phase difference is within a certain range, distortion greatly affects the characteristics of the semiconductor substrate. I found that I did not give. That is, the range is a phase difference of 50 nm or less per 100 μm thickness.

In an optically completely symmetric crystal without any distortion, this phase difference is zero. However, real crystals often have more or less strain. In a transparent crystal, the strain in the crystal can be quantified by evaluating this phase difference. It was found that even if the rocking curve of the (400) plane was also in the range of 10 to 80 seconds, a difference occurred in this phase difference. As the cause, we first focused on the impurities incorporated into the crystal. That is, it was found that the above phase difference can be realized when nitrogen and silicon are in the range of 0.01 to 100 ppm and 0.01 to 1000 ppm, respectively. Furthermore, the spin density obtained by electron spin resonance is 1 × 10 ¹⁷ / cm ³ or less in the range where the g value is 2.0020 or more and less than 2.0028, and a natural single crystal substrate is used as a seed substrate. Rather than using a seed crystal grown by a high-pressure synthesis method or a vapor phase synthesis method, mechanically polishing the side surface, etching and removing the main surface and the side surface by reactive ion etching, the main surface It has been found that the optical strain can be reduced over the entire crystal by including a step of newly growing a single crystal diamond layer by vapor phase synthesis.

When this invention is used as a substrate for a semiconductor device, the thickness is desirably 100 μm or more and 1500 μm or less. A larger diameter is better, but if it is 4 mm or more, it is a sufficient size for the device development process.
As a method for producing this substrate, it is desirable to include a step of separating the seed substrate from the newly grown single crystal layer by slicing with a laser beam having a wavelength of 360 nm or less as well as the seed substrate by a vapor phase synthesis method. . As a result, the processing loss can be suppressed as well as the method of scraping off the seed substrate by polishing or the like, as well as the laser slice exceeding the wavelength of 360 nm, which greatly contributes to cost reduction.

  As a seed substrate, it is preferable to use a substrate obtained by a gas phase synthesis method. It was found that the strain can be suppressed compared to using a seed substrate by a high-pressure synthesis method. This is because there is a difference in how defects are introduced and the amount and distribution of impurities between the high-pressure synthesis method and the single-phase method using the vapor phase synthesis method. Differences exist in characteristics such as expansion coefficient, and as a result, distortion accumulates. It has been found that if a gas phase synthesis method is used as a seed substrate, no strain is introduced into the newly grown single crystal layer even if the strain remains in the seed substrate.

Further, the side surface of the seed single crystal diamond substrate is mechanically polished, and then the main surface and side surfaces are etched away by reactive ion etching, and then a new single crystal diamond layer is grown by vapor phase synthesis. This has been found to have a great effect on distortion reduction.
It is desirable that the side surface after this polishing has an inclination with respect to the main surface within a range of 82 degrees or more and 98 degrees or less. With an inclination of 82 degrees or more and less than 90 degrees (a state in which the side faces are inclined upward), the lateral growth rate is increased during single crystal growth, and a large single crystal is easily obtained. On the contrary, if the tilt angle is 90 degrees or more (the side surface is tilted vertically or downward), the lateral growth rate is reduced, but it is effective for low strain growth and is more suitable for applications such as precision optical parts. .

  The surface roughness of the main surface and side surfaces of this polishing etc. is preferably 0.1 μm or less in Rmax and 10 nm or less in Ra. This surface roughness can be easily measured with an atomic force microscope. Further, chipping may occur in the corner portion of the substrate during polishing, but the size is desirably 50 μm or less. By satisfying these requirements, abnormal growth can be prevented during single crystal growth, and low strain growth can be realized.

  Furthermore, it is desirable to grow the single crystal after the mechanically polished seed substrate surface and main surface are etched away by RIE to 0.5 μm or more and less than 400 μm. In order to suppress the generation of strain during vapor phase growth of a diamond single crystal, it is sufficient to prepare a seed substrate that does not have a work-affected layer. It is difficult to remove by polishing. Various processes such as microwave plasma etching, ECR plasma etching, and ion beam etching are known as non-mechanical processing processes for diamond, including the RIE. In these non-mechanical processing processes, methods other than RIE are difficult to solve at the same time, such as the processing speed and processing area of the seed substrate, surface roughness after processing, and generation of a damaged layer during etching. . In RIE, only the work-affected layer of the seed substrate can be removed at high speed and flatness without damage. After that, by vapor-phase growth of the single crystal, it is possible to obtain a large-sized diamond single crystal substrate having no distortion and high quality.

The RIE of the present invention can be performed by a known method. The method is roughly divided into a method using capacitively coupled plasma (CCP) that connects a high-frequency power source to electrodes arranged opposite to each other in a vacuum vessel, and a high-frequency power source connected to a coil arranged so as to surround the vacuum vessel. There are systems that use inductively coupled plasma (ICP), and there are systems that combine both systems, but either system can be used in the present invention.
As the etching gas, a mixed gas of oxygen and fluorocarbon is used, and the etching pressure is desirably 1.33 Pa or more and 13.3 Pa or less. By using the gas type and pressure, it is possible to remove only the work-affected layer at high speed and flatly.

  The seed substrate main surface and side surface etching thickness in the present invention may be 0.5 μm or more and less than 400 μm, desirably 5 μm or more and less than 50 μm, more preferably 10 μm or more and less than 30 μm. The thinner the etching thickness, the shorter the processing time and the advantage of maintaining the flatness of the surface. The thickness of the work-affected layer of the seed substrate depends on the type and strength of polishing. Most of them are less than 0.5 μm, but in some rare cases, they may reach a depth of about 10 μm, and the characteristics as a semiconductor may deteriorate in a region grown from this portion. Conversely, if the etching depth is thick, not only etching time is required, but also surface roughness due to etching may be increased. In the subsequent single crystal growth, deterioration of crystallinity due to surface roughness may be observed.

The side surface of the seed substrate in the present invention is preferably etched away by 50 nm or more, more preferably 0.15 μm or more by the same RIE, and in particular when the side surface is also mechanically polished like the surface, it is etched by 0.5 μm or more. It is desirable to be removed. As a result, particularly when the lateral growth is performed during the growth of the single crystal thick film, it is possible to reduce the distortion of the region laterally grown from the side surface. As a method of RIE of the side surface, there is a method of simultaneously etching from the lateral direction when performing RIE of the seed substrate surface. However, when the substrate is placed upright and only the side surface is etched, the etching thickness is independently set. It is efficient because it can be controlled.
As for the etching of the side surface and the main surface, it is preferable to perform the side surface etching first. That is, in the side etching, it is necessary to arrange the substrate upright and cover the main surface, but the main surface may be damaged when covered. This damage can be removed by etching the main surface according to the present invention. The main surface of the seed substrate used is preferably (100) or approximately (100). If the surface orientation of the side surface of the seed substrate is approximately (100), the lateral growth rate is increased and a large single crystal is easily obtained.

(Comparative example)
Using a high pressure synthetic single crystal Ib substrate having a size of 4.0 × 4.0 × 0.4 mm as a seed substrate, homoepitaxial growth was performed by a vapor phase synthesis method. The principal surface is (100) (0.9 degrees off in the <110> direction). The growth conditions were a methane concentration of 10% (diluted with hydrogen), a pressure of 120 Torr, and a substrate temperature of 990 ° C. The growth time was 100 hours. After the growth, a YAG fundamental wave laser was incident from the side surface to separate the seed substrate and the vapor-phase synthesis single crystal layer. The vapor-phase synthesized single crystal layer is mirror-polished on both the growth surface and the substrate surface, and the outer periphery is subjected to shaping / cutting with a YAG fundamental wave laser, and then washed with dichromic acid to be 4.7 × 4. A sample A having a size of 7 × 0.35 mm was obtained (the main surface is (100), 0.8 degrees off in the <110> direction).

Example 1
Using the sample A (vapor phase synthesis seed substrate) obtained above, the growth was further continued under the same conditions as above, and a new vapor phase synthesis single crystal layer was obtained with a thickness of 700 μm. Prior to this growth, the main surface on which a single crystal layer is newly grown is etched away by a known high-frequency inter-electrode discharge (CCP) RIE. Etching conditions are shown below.

High frequency frequency: 13.56 MHz
High frequency power: 250W
Chamber pressure: 8Pa
O ₂ gas flow rate: 8 sccm
CF ₄ gas flow rate: 12sccm
When etching was performed for 7 hours under the above conditions, the main surface of the seed substrate was removed by 18 μm, and the surface roughness Rmax after etching was 0.1 μm, unchanged from that before etching.
The seed substrate was separated using a YAG third harmonic laser (wavelength 355 nm). The newly grown vapor-phase synthesized single crystal layer was mirror-polished on both the growth surface and the substrate surface, and was similarly cut and shaped by the laser YAG fundamental wave. And the sample B of 5.4x5.5x0.3mm was obtained.
The full width at half maximum, phase difference, resistivity, spin density, nitrogen impurity, and silicon impurity of the (400) plane of Samples A and B were measured. That is, the evaluation method is as follows.

1) The half width of the X-ray rocking curve was evaluated by a two-crystal method using CuKα1 X-rays and using a high-pressure synthetic single crystal diamond (400) plane parallel arrangement as the first crystal.
2) The phase difference was measured by the Senarmon method. That is, the quarter-wave plate and the polarizer are combined to convert the elliptically polarized light after passing through the sample into linearly polarized light, and the phase difference is obtained. A sodium lamp (wavelength 589 nm) was used as a measurement light source. The obtained phase difference was converted per sample thickness of 100 μm and evaluated. The measurement was performed using a polarizing microscope, and the maximum value was obtained by observing the entire sample.
3) The resistivity can be obtained by forming electrode metal on both surfaces of the sample, applying a predetermined electric field, and measuring the current value flowing at that time. The measurement was performed at room temperature of 20 ° C.
4) The spin density was determined by the ESR method. The measurement was performed at room temperature of 20 ° C. The central magnetic field was 3370 G, the magnetic field sweep width was 100 G, the microwave was 9.46 GHz, and the output was 0.01 to 0.16 mW. All measurements were performed with an external magnetic field applied in the <100> axis direction of the single crystal.
From the obtained spectrum, the spin density in the range of g value of 2.0020 or more and less than 2.0028 was calculated.
5) Nitrogen impurity concentration and silicon impurity concentration were evaluated by SIMS analysis. In the SIMS analysis, Cs ⁺ was used as the primary ion, and the concentration at an acceleration voltage of 15 kV and a detection region of 35 μmΦ was obtained at a place where 0.5 μm was sputtered from the sample outermost surface. The concentration was determined by comparison with a separately prepared standard sample (diamond single crystal with known impurity concentration prepared by ion implantation).

The results are shown in Table 1.
Both samples A and B have excellent rocking curve half widths of just over 20 seconds, but the phase difference varies greatly depending on the location of sample A. For this reason, the resistivity is lowered to the 11th power. In such a sample, there is a concern that the device characteristics may be affected in an electronic device application that requires a high breakdown voltage. This is because the amount of strain varies depending on the location of the sample because the seed substrate is high-pressure synthetic single crystal diamond and the etching process before growth is not performed.
Sample B is expected to have a sufficient withstand voltage and can be used as a substrate for high-quality electronic devices.

(Example 2)
Sample A ′ was produced under the same conditions as Sample B, using Sample A ′ produced under the same conditions as Sample A as the substrate. However, before this growth, all side surfaces of the sample A ′ were first etched with the sample standing, and then the main surface on which a single crystal layer was newly grown was etched. Etching conditions are the same as in Example 1. Each of the four side surfaces was etched for 5 hours and the main surface was etched for 9 hours, so that the side surfaces were etched by 10 to 15 μm and the main surface was etched by 24 μm.
Table 1 shows the results of evaluation similar to Example 1 for Sample C.
The full width at half maximum of the rocking curve is slightly worse than that of the sample B, but the maximum value of the phase difference is as good as 25 nm. This is because the distortion starting from the vicinity of the side surface of the seed substrate is reduced by the etching process on the side surface, and when applied as a substrate for an electronic device, it can be used as a high-quality substrate, similar to Sample B. It is expected. Both samples B and C are considered to exhibit excellent characteristics not only as substrates for electronic devices but also as optical components.

(Example 3)
Six high pressure synthetic single crystal Ib substrates having a size of 4.0 × 4.0 × 0.4 mm were prepared as seed substrates. The surface orientation of the main surface and the side surface was (100), and when the side surface was mechanically polished, the angle with the main surface was changed for each substrate. The main surface and side surfaces were polished using a revolution / dry type polishing apparatus. The polishing load was 1 kg. The peripheral speed of the grindstone was 30 m / s, and the polishing time was 10 minutes for the main surface and 5 minutes for each side surface. The roughness of the main surface and side surfaces after polishing is Rmax = 0.1 μm, Ra = 2.
It was 5 nm. Chips generated during polishing existed on a part of the side surface of the substrate, but the size was 1 μm or less.
For these substrates, the seed substrate side surface was first etched under the same conditions as in Example 1 and then the main surface was etched. The etching amount was changed by adjusting the time for each substrate. Thereafter, a vapor-phase synthesis single crystal was grown under the same conditions as in Sample A. Further, for each sample, the vapor-phase synthesized single crystal layer was taken out using a laser in the same procedure as in the preparation of Sample A, and double-side polishing was performed to measure each crystallinity.
Table 2 shows the results of the same evaluation as in Example 1 for the vapor-phase synthesized single crystal samples D to I thus obtained.

Samples D to I in Table 2 are comparisons when the angle between the main surface and the side surface is changed. In sample D, the main surface and side surfaces were polished perpendicularly to each other, and as a result, the phase difference of the obtained vapor-phase synthesized single crystal was 5 nm, which was smaller than that of sample C. In Sample E, the angle between the main surface and the side surface of the seed substrate was 86 degrees, and the lateral growth rate of the obtained vapor-phase synthesized single crystal was faster than that of Sample C, but the phase difference was worse than that of Sample A. In Sample F, the angle between the main surface and the side surface of the seed substrate was 94 degrees, and the phase difference of the obtained vapor-phase synthesized single crystal was the smallest value of 1 nm.
Samples G and H are comparative examples in which the angle between the main surface and the side surface is smaller or larger. In either case, as a result of the face orientation of the side face deviating greatly from (100), the crystallinity of the lateral growth region deteriorated and the phase difference increased. Sample I is a comparative example in which the etching amount on the main surface and side surfaces is reduced. Due to insufficient etching, the crystallinity of the single crystal layer deteriorated during the subsequent vapor phase synthesis, resulting in an increase in the phase difference.

Claims (12)

  Irradiation of linearly polarized light, which is regarded as a combination of two mutually orthogonal linearly polarized lights, from one principal surface, the phase difference between two mutually orthogonally linearly polarized lights emitted from the principal surface of the opposite surface is the sample thickness of 100 μm throughout the sample. Single-crystal diamond grown by vapor phase synthesis characterized by a maximum of 50 nm or less per unit.   The single crystal diamond according to claim 1, wherein the diamond has a thickness of 100 µm or more and 1500 µm or less. The single crystal diamond according to claim 1, wherein the resistivity at room temperature is 10 ¹² Ωcm or more. 2. The single crystal according to claim 1, wherein the spin density obtained by electron spin resonance is 1 × 10 ¹⁷ / cm ³ or less at room temperature in a range of g value of 2.0020 to less than 2.0028. diamond.   The single crystal diamond according to claim 1, wherein the concentration of nitrogen atoms as impurities is 0.01 ppm to 100 ppm.   The single crystal diamond according to claim 1, wherein the concentration of silicon atoms as impurities is 0.01 ppm to 1000 ppm.   The single crystal diamond according to claim 1, wherein the main surface and the side surface are substantially (100) surfaces. A step of etching and removing one principal surface of a single crystal diamond substrate to be a seed by reactive ion etching, and then newly growing a single crystal diamond layer by a vapor phase synthesis method;
Including a step of separating a single crystal diamond substrate to be a seed and a single crystal diamond layer newly grown by a vapor phase synthesis method,
A method for producing single crystal diamond, wherein the single crystal diamond substrate as the seed is grown by a high pressure synthesis method or a vapor phase synthesis method.   9. The method for producing single crystal diamond according to claim 8, further comprising a step of mechanically polishing a side surface of the single crystal diamond substrate to be the seed before the step of growing the single crystal diamond layer.   The single crystal diamond manufacturing method according to claim 9, wherein the mechanical polishing step causes the inclination of the side surface of the single crystal diamond substrate to be within a range of 82 degrees to 98 degrees with respect to the main surface. Method.   After the step of mechanically polishing the side surface of the seed single crystal diamond substrate, and before the step of growing the single crystal diamond layer, the step of etching and removing the side surface by reactive ion etching The method for producing a single crystal diamond according to claim 9 or 10, wherein   The thickness removed by etching in the step of etching and removing one main surface and / or side surface of the single crystal diamond substrate as a seed by reactive ion etching is 0.5 μm or more and less than 400 μm. A method for producing a single crystal diamond according to 8 or 11.