Diamond Substrate

Abstract

A method for manufacturing a diamond substrate capable of sufficiently reducing dislocation defects, a high-quality diamond substrate, and a free-standing diamond substrate are provided. [Solution] A method for manufacturing a diamond substrate, comprising: a first step of providing a pattern of diamonds on a base surface; a second step of growing diamonds from the pattern of diamonds provided in the first step, thereby forming diamonds in the gaps between the pattern of diamonds provided in the first step; a third step of removing the pattern of diamonds provided in the first step, thereby forming a pattern of diamonds made from the diamonds formed in the second step; and a fourth step of growing diamonds from the pattern of diamonds formed in the third step, thereby forming diamonds in the gaps between the pattern of diamonds formed in the third step.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a diamond substrate, a diamond substrate, and a free-standing diamond substrate. [Background technology]

[0002] Diamond has a wide band gap of 5.47 eV at room temperature and is known as a wide band gap semiconductor.

[0003] Among semiconductors, diamond has a very high breakdown field strength of 10 MV / cm, making it possible to operate at high voltages. It also has the highest thermal conductivity of any known substance, making it excellent at dissipating heat. Furthermore, its extremely high carrier mobility and saturated drift velocity make it suitable for use in high-speed devices.

[0004] For this reason, diamond has the highest Johnson figure of merit, which indicates the performance of high-frequency, high-power devices, even when compared with semiconductors such as silicon carbide and gallium nitride, and is said to be the ultimate semiconductor.

[0005] Thus, diamond is expected to be put to practical use as a semiconductor material, and there is a demand for large-area, high-quality diamond substrates, but diamond substrates of sufficient quality have yet to be obtained.

[0006] Currently, type Ib diamonds synthesized by the high pressure, high temperature (HPHT) method are used as diamond substrates. However, type Ib diamonds contain a lot of nitrogen impurities and can only be obtained in a maximum size of about 8 mm square, so they are not very practical.

[0007] In Non-Patent Document 1, a Schottky diode is fabricated using a diamond substrate synthesized by the HPHT method. However, the etch pit density by hydrogen plasma treatment, which is an indicator of the dislocation defect density of the diamond substrate, is 105 cm -2 It has been reported that even when electrodes are actually formed and operation is attempted, malfunctions occur due to the presence of killer defects near the electrodes or in the current path.

[0008] In some cases, homoepitaxial diamond is epitaxially grown by chemical vapor deposition (CVD) on a base of diamond synthesized by the HPHT method, and used as a substrate.

[0009] In Non-Patent Document 2, an attempt was made to fabricate a mosaic-shaped diamond substrate by bonding multiple diamond substrates in order to obtain a large diamond substrate. However, such a technique has problems such as the tendency for cracks to occur along the boundaries of the substrates.

[0010] On the other hand, the production of diamond substrates by heteroepitaxial growth, in which diamond is grown on a different material, is also being considered. Heteroepitaxial growth is expected to make it relatively easy to obtain large-area substrates and reduce manufacturing costs.

[0011] Silicon (Si), platinum (Pt), etc. have been considered as substrates for heteroepitaxial growth of diamond, and non-patent document 3 reports that iridium (Ir) is suitable as a substrate material. This involves using Ir epitaxially grown on the surface of single crystal magnesium oxide (MgO) as a substrate material, subjecting this surface to diamond nucleation treatment, and then producing epitaxial diamond by the DC plasma CVD method.

[0012] However, heteroepitaxial growth also has the problem of many dislocation defects occurring due to the lattice mismatch between diamond and the base material. For example, the lattice mismatch between diamond (lattice constant 3.57 Å) and Ir (lattice constant 3.84 Å) is large at 7%. Non-Patent Document 4 reports that the etch pit density of heteroepitaxial diamond is 108 cm -2 There have been reports that it can even cause

[0013] As a method for reducing such dislocation defects, Non-Patent Document 5 proposes a technique called selective growth, which is a method for laterally growing diamond from diamond nuclei formed in an arbitrary pattern (ELO: Epitaxial Lateral Overgrowth). [Prior art documents] [Non-patent literature]

[0014] [Non-Patent Document 1] H. Umezawa et al., Diamond Relat. Mater., 18, 1196 (2009) [Non-Patent Document 2] H.Yamada et al.,Appl.Phys.Lett.,104,102110(2014) [Non-Patent Document 3] K. Ohtsuka et al., Jpn. J. Appl. Phys., 35, L1072 (1996) [Non-Patent Document 4] K.Ichikawa et al.,Proc.24th NDF-Dia.Sympo.,226(2010) [Non-Patent Document 5] Atsuhito Sawabe et al., Journal of the Japanese Society for Crystal Growth, 39, 179 (2012). Summary of the Invention [Problem to be solved by the invention]

[0015] Although the selective growth method described above can reduce dislocation defects to a certain extent, further reduction in defects is required for practical use.

[0016] In addition, in heteroepitaxial growth, thermal stress is also generated due to the difference in thermal expansion coefficient between diamond and the base material. For example, the linear expansion coefficient of diamond is 1.1 × 10 -6 K -1 and for MgO it is 13.8 × 10 -6 K -1 , 7.1 × 10 for Ir -6 K -1 Furthermore, it is known that large internal stresses occur in diamond as the crystal grows, and these stresses can cause cracks and warping of the diamond substrate.

[0017] In fact, many cracks have been generated in the heteroepitaxial diamond substrate fabricated by the selective growth method described in Non-Patent Document 5, and it is considered difficult to put it to practical use in this state.

[0018] Therefore, in order to put diamond substrates produced by epitaxial growth into practical use, it is also hoped that thermal stress and internal stress will be reduced.

[0019] The present invention has been made in consideration of the above circumstances, and aims to provide a method for manufacturing a diamond substrate capable of sufficiently reducing defects (including dislocation defects), a high-quality diamond substrate with sufficiently reduced defects, and a diamond free-standing substrate. [Means for solving the problem]

[0020] In order to solve the above problems, the present invention provides a method for manufacturing a diamond substrate, comprising the steps of: A first step of providing a pattern of diamonds on a substrate surface; a second step of growing diamond from the patterned diamond provided in the first step to form diamond in the patterned diamond provided in the first step; a third step of removing the patterned diamonds provided in the first step and forming a patterned diamond made of the diamonds formed in the second step; A fourth step of growing diamond from the patterned diamond formed in the third step to form diamond in the patterned diamond formed in the third step; The present invention provides a method for producing a diamond substrate, comprising the steps of:

[0021] Such a method for manufacturing a diamond substrate can sufficiently reduce defects in the diamond substrate, making it possible to manufacture high-quality diamond.

[0022] In this case, the material constituting the base surface may be diamond.

[0023] In this way, by using diamond as the material constituting the base surface, a diamond substrate is manufactured by homoepitaxial growth.

[0024] The material constituting the base surface may be a different material other than diamond, such as iridium, rhodium, or platinum.

[0025] In this way, when diamond is grown heteroepitaxially using a base whose surface is made of a different material, it is possible to fabricate a high-quality, large-area diamond substrate.

[0026] Furthermore, in the method for manufacturing a diamond substrate of the present invention, it is preferable to remove any foreign matter adhering to the wall surfaces of the patterned diamond formed on the base surface in the first step prior to the second step.

[0027] By removing the foreign matter in this manner, the generation of abnormally grown particles can be suppressed in the second step which is carried out next.

[0028] It is also preferable that the ratio D / W of the depth D to the width W of the pattern gaps in the patterned diamond provided in the first step is 0.1 or more.

[0029] In this way, if a pattern of diamond is provided in the first step so that the ratio (D / W) of the depth D to the width W of the pattern gap is equal, the pattern gap will be closed relatively quickly in the second step, so that even if abnormally grown particles occur in the pattern gap, the impact on the surface of the formed diamond can be reduced.

[0030] It is also preferable that at least a part of the bottom of the pattern gaps in the patterned diamond provided in the first step is penetrated.

[0031] In addition, when the material constituting the base surface is a different material other than diamond, at least a part of the bottom of the pattern gaps in the patterned diamond provided in the first step may be provided below the base surface.

[0032] In this way, it is possible to manufacture a diamond substrate in which the internal stress generated during crystal growth is alleviated, and also in which the thermal stress generated when the base is made of a different material is alleviated.

[0033] In the second step, it is preferable to grow diamond by chemical vapor deposition.

[0034] Thus, in the second step, diamond can be grown using a variety of chemical vapor deposition techniques.

[0035] It is also preferable to form voids in the diamond grown in the second step.

[0036] Thus, forming voids in diamond is preferable because it can reduce internal stress that occurs with crystal growth and thermal stress that occurs when the base is made of a different material.

[0037] It is also preferable to remove foreign matter adhering to the wall surface of the patterned diamond formed in the third step before the fourth step.

[0038] By removing the foreign matter in this manner, the generation of abnormally grown particles can be suppressed in the fourth step which is carried out next.

[0039] It is also preferable that the ratio D / W of the depth D to the width W of the pattern gaps in the patterned diamond formed in the third step is 0.1 or more.

[0040] In this way, the gaps between the patterns are filled relatively quickly in the fourth step, so that even if abnormally grown grains arise from the gaps between the patterns, the effect on the surface of the formed diamond can be reduced.

[0041] It is also preferable that at least a part of the bottom of the pattern gaps in the patterned diamond formed in the third step is penetrated.

[0042] In addition, when the material constituting the base surface is a different material other than diamond, at least a part of the bottom of the pattern gap in the patterned diamond formed in the third step may be located below the base surface.

[0043] In this way, it is possible to manufacture a diamond substrate in which the internal stress that occurs with crystal growth and the thermal stress that occurs when the base is made of a different material are alleviated.

[0044] In the third step, the diamond formed in the second step is preferably removed to a position 5 μm to 30 μm from the boundary with the patterned diamond provided in the first step.

[0045] By removing the diamond formed in the second step in this manner, a diamond of higher quality can be grown in the fourth step, and this is also preferable from the standpoint of production efficiency and production costs.

[0046] In the fourth step, it is preferable to grow diamond by chemical vapor deposition.

[0047] Thus, in the fourth step, diamond can be grown using various chemical vapor deposition techniques.

[0048] It is also preferable to form voids in the diamond grown in the fourth step.

[0049] Thus, forming voids in diamond is preferable because it can reduce internal stress that occurs with crystal growth and thermal stress that occurs when the base is made of a different material.

[0050] The present invention also provides a diamond substrate having diamond as a material constituting at least one surface, the diamond substrate being characterized in having voids therein.

[0051] The diamond substrate may comprise a base and a diamond layer formed on the surface of the base, and may have voids in contact with the boundary between the base and the diamond layer.

[0052] The present invention also provides a free-standing diamond substrate, characterized in that one surface of the substrate has voids.

[0053] Such a diamond substrate having voids therein and a diamond freestanding substrate having voids on one surface thereof have sufficiently reduced defects such as dislocation defects, and also have reduced stress, making it possible to suppress the occurrence of warping and cracks in the substrate.

[0054] The present invention also provides a diamond substrate comprising a base and a diamond layer formed on the surface of the base, the diamond substrate being characterized in that the back surface of the base has an opening.

[0055] Such a diamond substrate has sufficiently reduced defects, and also has reduced internal stress that occurs with crystal growth and thermal stress that occurs when the base is made of a different material, making it possible to suppress the occurrence of warping or cracks in the substrate.

[0056] The present invention also provides a diamond substrate having at least one surface made of a material that is diamond, characterized in that at least one of the entire surfaces is made of at least one of laterally grown diamond and diamond grown from a laterally grown diamond layer.

[0057] Such a diamond substrate has sufficiently reduced defects and low stress. Effect of the Invention

[0058] According to the present invention, it is possible to provide a high-quality diamond substrate with few defects (including dislocation defects) and small stress. By using such a diamond substrate, it is possible to manufacture semiconductor devices that exhibit excellent performance. Furthermore, when diamond is grown heteroepitaxially using a different material as the base, it is possible to simultaneously realize a large-area diamond substrate. [Brief description of the drawings]

[0059] [Figure 1] FIG. 2 is a diagram showing a schematic diagram of a method for producing a diamond substrate according to the present invention (Example 2). [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of lithography and the like carried out in a first step in the method for producing a diamond substrate according to the present invention (Example 2). [Diagram 3]FIG. 2 is a diagram showing a schematic diagram of another method (Example 1) for manufacturing a diamond substrate according to the present invention. [Figure 4] FIG. 2 is a diagram showing a schematic diagram of lithography and the like carried out in a first step in another method (Example 1) for producing a diamond substrate according to the present invention. [Diagram 5] 1 is a cross-sectional view showing an example of a diamond substrate of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] As described above, there is a demand for a manufacturing method of a diamond substrate that can sufficiently reduce defects (including dislocation defects), and for a high-quality diamond substrate and a free-standing diamond substrate with sufficiently reduced defects.

[0061] The present inventors have found that the following method for producing a diamond substrate according to the present invention makes it possible to produce a high-quality diamond substrate with sufficiently reduced defects.

[0062] That is, the present invention is a method for producing a diamond substrate, A first step of providing a pattern of diamonds on a substrate surface; a second step of growing diamond from the patterned diamond provided in the first step to form diamond in the patterned diamond provided in the first step; a third step of removing the patterned diamonds provided in the first step and forming a patterned diamond made of the diamonds formed in the second step; A fourth step of growing diamond from the patterned diamond formed in the third step to form diamond in the patterned diamond formed in the third step; The present invention provides a method for producing a diamond substrate, comprising the steps of:

[0063] The following describes the embodiments of the present invention with reference to the drawings, but the present invention is not limited thereto. The method for producing diamond of the present invention includes at least the four steps described below, but other steps can be added as necessary.

[0064] First, in the first step, diamonds 2, 22 in a pattern are provided on the surfaces (substrate surfaces) of substrates 1, 21 (FIGS. 1(A), 3(A)).

[0065] In this case, there is no particular limitation on the material that constitutes the underlayer 1, 21. As shown in Fig. 1, if the material that constitutes the underlayer surface is diamond 3, a diamond substrate is produced by homoepitaxial growth.

[0066] Examples of such a substrate 1 include diamond 3 such as diamond synthesized by the HPHT method, homoepitaxial diamond, and heteroepitaxial diamond. In particular, if diamond with relatively few defects such as diamond synthesized by the HPHT method or homoepitaxial diamond is used as the substrate, a diamond substrate with even fewer defects can be produced.

[0067] On the other hand, if the material constituting the base surface is a different material other than diamond, as shown in Figure 3, a diamond substrate can be produced by heteroepitaxial growth.

[0068] The heterogeneous material that constitutes the base surface is preferably a material that is a cubic crystal like diamond, has a small lattice mismatch with diamond, and does not react with carbon to form carbides. Materials that satisfy these conditions include the platinum group metals, such as rhodium (Rh), palladium (Pd), iridium (Ir), and platinum (Pt).

[0069] Here, the lattice constant of diamond is 3.57 Å, and the lattice mismatch with Rh (lattice constant 3.72 Å) is 4.2%, with Ir (lattice constant 3.84 Å) is 7.6%, and with Pt (lattice constant 3.92 Å) is 9.8%. The lattice mismatch between diamond and the different materials constituting the base surface is preferably 10% or less. Also, Ir is preferable from the viewpoint of not reacting with carbon to form carbides.

[0070] An example of such a base 21 is a base having an intermediate layer 24 made of a material selected from single crystal magnesium oxide (MgO), single crystal strontium titanate (SrTiO3), α-alumina (Al2O3), and yttria-stabilized zirconia (YSZ) provided on a silicon (Si) substrate 23, and further having a surface layer 25 made of a material selected from iridium (Ir), rhodium (Rh), and platinum (Pt) provided on the intermediate layer.

[0071] In addition, one or more layers (not shown) made of a material selected from gold (Au), platinum (Pt), titanium (Ti), chromium (Cr), iridium (Ir), rhodium (Rh), silicon (Si), and silicon oxide (SiO2) may be interposed between the silicon (Si) substrate 23 and the intermediate layer 24.

[0072] Heteroepitaxial growth makes it possible to easily obtain large-area diamond substrates at relatively low cost. Therefore, by applying heteroepitaxial growth to the present invention, it is possible to produce high-quality, large-area diamond substrates.

[0073] There is also no limitation on the method for providing the patterned diamonds 2, 22 on the base surface. In the present invention, the term "patterned" refers to a pattern formed by projections and recesses.

[0074] When the material constituting the base surface is diamond, for example, diamond 3 on the base surface can be processed into a patterned diamond 2 by a known method such as photolithography or electron beam lithography (Figure 1(A)).

[0075] When the material constituting the base surface is a different material, first, diamond is grown on the base surface by a known method such as microwave plasma CVD, direct current plasma CVD, hot filament CVD, arc discharge plasma jet CVD, etc. Next, the diamond grown on the base surface is processed into a pattern by a method such as photolithography or electron beam lithography, so that a patterned diamond 22 can be provided on the base surface (FIG. 3(A)).

[0076] Furthermore, even if the material constituting the base surface is diamond, diamond may be grown on the base surface by a similar technique and the grown diamond may be processed into a pattern to provide a patterned diamond on the base surface.

[0077] The shape of the pattern of the diamonds 2, 22 provided on the base surface can be selected arbitrarily. For example, the pattern can be a line, rectangular dot, circular dot, or other pattern of diamonds arranged in a plurality of dots.

[0078] At this time, the position, size, thickness, crystal orientation, etc. of the patterned diamonds 2, 22 can be arbitrarily selected, but the depth D of the pattern gaps 10, 30 in the patterned diamonds 2, 22 (D in FIG. 1) 11 , D in Fig. 3 21 ) and width W (W in Fig. 1) 12 , W in Figure 3 22 It is preferable that the ratio D / W is 0.1 or more, and more preferably 0.5 or more. 11 , W in Figure 3 21 is the width of the convex portion in the patterned diamond 2, 22. In this way, the pattern gaps 10, 30 are filled relatively quickly in the second step, so that even if abnormally grown particles are generated from the pattern gaps, the effect on the formed diamond surface can be reduced. In the present invention, the "pattern gap" refers to the gap between the convex portions of the patterned diamond.

[0079] The material constituting the bottoms 11, 31 of the pattern gaps 10, 30 may be diamond or a different material. However, since materials such as MgO are etched by hydrogen (H2) / methane (CH4) plasma of CVD when diamond is formed in the pattern gaps in the second step, it is preferable to use a material such as Ir.

[0080] In particular, when the material constituting the bottom of the pattern gap is a different material, in the process of processing the diamond into a pattern, a different kind of attachment may adhere to the wall surface of the pattern-shaped diamond 2, 22 provided on the base surface. In addition, a different kind of attachment may adhere due to SiO2 used as a mask. It is preferable to remove the different kind of attachment adhered to the wall surface of the pattern-shaped diamond provided on the base surface before the second process. By removing the different kind of attachment adhered to the wall surface of the diamond in this way, the generation of abnormally grown particles can be suppressed in the second process. The removal of the different kind of attachment can be performed, for example, by selective etching or the like.

[0081] For example, when foreign deposits such as Ir or SiO2 are attached to the wall surfaces of the patterned diamonds 2, 22 provided on the base surface, they can be removed by etching with CF4 plasma.

[0082] Furthermore, if necessary, at least a part of the bottoms 11, 31 of the pattern gaps 10, 30 in the patterned diamond provided in the first step may be removed together with the underlying layer to form a through hole.

[0083] When the material constituting the base surface is a different material other than diamond, at least a part of the bottom 31 of the pattern gap 30 in the patterned diamond provided in the first step may be provided below the base surface by removing a part of the base. In this case, the depth from the base surface to the bottom 31 of the pattern gap 30 can be determined arbitrarily.

[0084] In this way, it is possible to reduce internal stress and thermal stress that occurs when the base is made of a different material. As a method for removing the base as well, for example, etching can be used.

[0085] In the second step, diamond is grown from the patterned diamonds 2, 22 provided in the first step, and diamonds 12, 32 are formed in the pattern gaps 10, 30 in the patterned diamonds 2, 22 provided in the first step (Figures 1(B) and 3(B)).

[0086] The method for growing diamonds 12, 32 from the patterned diamond provided in the first step may be selected from known methods such as microwave plasma CVD, direct current plasma CVD, hot filament CVD, and arc discharge plasma jet CVD.

[0087] At this time, diamond grows laterally (ELO: Epitaxial Lateral Overgrowth) using the patterned diamond as a nucleus, so that diamonds 12 and 32 with few defects are formed in the gaps between the patterns.

[0088] Moreover, it is not always necessary to form diamond so as to fill all of the pattern gaps.

[0089] When the diamonds 12 and 32 are grown in the second step, if the growth rate is made faster from the top of the diamond pattern than from the bottom, it is possible to form voids at the bottom of the gaps between the patterns. By forming such voids, stress can be relieved, and in particular, it is preferable to relieve thermal stress that occurs when the base is made of different materials. The voids to be formed can be, for example, approximately triangular voids with a cross section of 0.01 μm to 20 μm on each side.

[0090] To adjust the growth rate at the bottom and top of the patterned diamond, it is possible to control the ratio of growth rates for each crystal orientation by adjusting the source gas (e.g., methane) concentration, pressure, input power, etc.

[0091] Next, in the third step, the patterned diamonds 2 and 22 provided in the first step are removed, and patterned diamonds 13 and 33 made of the diamonds formed in the second step are formed (FIGS. 1(C) and 3(C)). This step can be performed by using a known method such as photolithography or electron beam lithography.

[0092] Moreover, it is not necessary to remove all of the patterned diamonds 2, 22 provided in the first step, and the diamonds 12, 32 formed in the second step may be partially removed as necessary.

[0093] At this time, it is preferable to remove the diamonds 12, 32 formed in the second step to a position 5 μm or more from the boundary with the patterned diamonds 2, 22 provided in the first step. This allows a diamond of higher quality to be grown in the fourth step. Also, from the viewpoint of manufacturing efficiency and manufacturing cost, it is preferable that the region to be removed is a position 30 μm or less from the boundary with the patterned diamonds 2, 22 provided in the first step.

[0094] In the third step, as in the first step, the shape of the pattern of the diamonds 13, 33 can be selected arbitrarily. For example, a pattern in which a plurality of diamonds are arranged in a line shape, a rectangular dot shape, a circular dot shape, or the like can be used.

[0095] At this time, the position, size, thickness, crystal orientation, etc. of the patterned diamonds 13, 33 can be arbitrarily selected, but the depth D of the pattern gaps 14, 34 in the patterned diamonds 13, 33 (D in FIG. 1) 12 , D in Fig. 3 22 ) and width W (W in Fig. 1)14 , W in Figure 3 24 It is preferable that the ratio D / W is 0.1 or more, and more preferably 0.5 or more. 13 , W in Figure 3 23 is the width of the convex portion in the patterned diamond 13, 33. In this way, the pattern gaps 14, 34 are filled relatively quickly in the fourth step, so that even if abnormally grown particles occur in the pattern gaps 14, 34, there is little effect on the surface of the formed diamond.

[0096] The material constituting the bottoms 15, 35 of the pattern gaps 14, 34 may be diamond or a different material. However, since materials such as MgO are etched by hydrogen (H2) / methane (CH4) plasma of CVD when diamond is formed in the pattern gaps in the fourth step, it is preferable to use a material such as Ir.

[0097] In particular, when the material constituting the bottom of the pattern gap is a different material, a different attachment may adhere to the wall surface of the diamond in the process of processing the diamond into a pattern. Also, a different attachment such as SiO2 used as a mask may adhere. It is preferable to remove such a different attachment adhered to the wall surface of the diamond before the fourth process. By removing the different attachment adhered to the wall surface of the diamond in this way, the generation of abnormally grown particles can be suppressed in the fourth process. The removal of the different attachment can be performed, for example, by selective etching.

[0098] For example, if Ir or SiO2 adheres to the wall surface of a diamond, it can be removed by etching with CF4 plasma.

[0099] Furthermore, if necessary, at least a part of the bottoms 15, 35 of the pattern gaps 14, 34 in the patterned diamonds 13, 33 formed in the third step may be penetrated.

[0100] When the material constituting the base surface is a different material other than diamond, at least a part of the bottom 35 of the pattern gap 34 in the patterned diamond 33 formed in the third step may be disposed below the base surface by partially removing the base as well.

[0101] It is believed that this will alleviate internal stress and thermal stress that occurs when the base is made of different materials.

[0102] In the fourth step, diamond is grown from the patterned diamonds 13, 33 formed in the third step, and diamonds 16, 36 are formed in the pattern gaps 14, 34 in the patterned diamonds 13, 33 formed in the third step (Figures 1(D) and 3(D)).

[0103] In the fourth step, as in the second step, the method for growing diamond from the patterned diamond provided in the third step may be selected from known methods such as microwave plasma CVD, direct current plasma CVD, hot filament CVD, arc discharge plasma jet CVD, etc.

[0104] At this time, diamond grows laterally (ELO: Epitaxial Lateral Overgrowth) using the patterned diamond as a nucleus, so diamond with few defects is formed in the gaps between the patterns.

[0105] Also, in the fourth step, it is not necessary to form diamond so as to completely fill the pattern gaps 14, 34, and it is preferable to form voids at the bottoms of the pattern gaps 15, 35. In both the second and fourth steps, forming such voids can relieve stress, and in particular can further relieve thermal stress that occurs when the base is made of a different material.

[0106] In the present invention, by the first to fourth steps, it is possible to produce diamond substrates 17, 37 whose entire surface consists of laterally grown diamond and / or diamond grown from laterally grown diamond.

[0107] That is, according to the present invention, there is provided a diamond substrate, the material constituting at least one surface of which is diamond, characterized in that the entirety of at least one surface is composed of at least one of laterally grown diamond and diamond grown from laterally grown diamond.

[0108] Furthermore, it is not necessary for the entire surface to be made of laterally grown diamond and / or diamond grown from laterally grown diamond by the fourth step, and further, by repeating the formation and growth of patterned diamond multiple times following the third and fourth steps, a diamond substrate may be produced in which at least one of the entire surfaces is made of at least one of laterally grown diamond and diamond grown from laterally grown diamond.

[0109] Also, after the entire surface is made of at least one of laterally grown diamond and diamond grown from laterally grown diamond, by repeating the formation and growth of patterned diamond several times according to the third and fourth steps, it is possible to further reduce defects.By this method, it is also possible to form more voids, so it is also possible to further reduce stress.

[0110] The diamond substrate produced according to the present invention may be used with the undercoat remaining, or may be used as a free-standing substrate after removing the undercoat.

[0111] When the base of the diamond substrate is removed to form a free-standing substrate, the free-standing substrate preferably has a thickness of 50 μm or more and 2000 μm or less. If the free-standing substrate has a thickness of 50 μm or more, it is preferable because it is easy to handle and unlikely to be damaged in the manufacturing process or the device manufacturing process using the diamond substrate.

[0112] On the other hand, when the thickness of the free-standing substrate is 2000 μm or less, there is no risk of the time required for simply forming diamond being long, and there is no risk of the unevenness of the diamond substrate surface becoming large, so the time required for polishing can be shortened. Therefore, the manufacturing cost can be reduced. Furthermore, the warping of the substrate can be suppressed, and the occurrence of cracks and breakage can be suppressed.

[0113] When the diamond substrate is to have a substrate structure including the substrate, leaving the substrate as is, the diamond layer does not need to be formed thicker than necessary. Considering the time required to prepare the substrate and the effect of internal stress, it is preferable that the thickness from the substrate surface to the substrate surface is 300 μm or less.

[0114] Furthermore, when voids are formed at the bottom of the pattern gaps in the second and / or fourth steps, a diamond substrate 100 having at least one surface 101 made of diamond and having voids 52 therein is obtained, as shown in FIG. 5.

[0115] In this case, the diamond substrate 100 of the present invention comprises a base 50 and a diamond layer 51 formed on the surface of the base 50, and may have a void 52 adjacent to the boundary between the base 50 and the diamond layer 51.

[0116] Furthermore, when the base 50 is removed to provide a free-standing substrate, the resulting diamond substrate has voids 52 on one surface.

[0117] The diamond substrate having voids inside the substrate and the free-standing diamond substrate having voids on one surface of the present invention have sufficiently reduced defects such as dislocation defects.Furthermore, since the stress is reduced, the occurrence of warping and cracks in the substrate can be suppressed.

[0118] Furthermore, when the bottom of the pattern gap is penetrated in the first and / or third steps, a diamond substrate is obtained which is composed of a base and a diamond layer formed on the surface of the base, and which is characterized in that the back surface of the base has an opening.

[0119] Such a diamond substrate having an opening in the surface of the base of the present invention has sufficiently reduced defects and also has reduced internal stress and thermal stress that occur with crystal growth, making it possible to suppress the occurrence of warping and cracks in the substrate.

[0120] The surface of the diamond substrate produced according to the present invention is preferably made of single crystal diamond.

[0121] On the surface of the diamond substrate produced by the present invention, a material selected from p-type diamond doped with impurities such as boron (B), n-type diamond doped with impurities such as phosphorus (P), and diamond not doped with impurities can be laminated. By using such a configuration, it becomes possible to operate as a semiconductor device. EXAMPLES

[0122] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0123] Example 1 A diamond substrate was manufactured by the method shown in FIG.

[0124] First, as shown in Fig. 3(A), a pattern of diamonds 22 was provided on the surface of a base 21 (first step). Specifically, the pattern of diamonds 22 was provided on the surface of the base 21 through the steps shown in Fig. 4(a) to Fig. 4(f).

[0125] The substrate 21 was prepared and the diamond layer 26 was formed on the substrate 21 as follows (FIG. 4(a)).

[0126] First, a single crystal silicon (Si) substrate 23 was prepared, which had a diameter of 10.0 mm, a thickness of 1.0 mm, and a surface of (100) plane, and was polished on both sides. A layer 24 made of single crystal MgO was formed on one side of the prepared single crystal silicon substrate 23 by electron beam deposition. At this time, the conditions were a substrate temperature of 900°C in a vacuum, and the single crystal MgO layer 24 was epitaxially grown until it reached 1 μm. Furthermore, a layer 25 made of Ir was formed on the single crystal MgO layer 24. The Ir layer 25 was formed by radio frequency (RF) magnetron sputtering (13.56 MHz) using an Ir target with a diameter of 6 inches (150 mm), a thickness of 5.0 mm, and a purity of 99.9% or more. The substrate on which the single crystal MgO layer 24 was formed was heated to 800°C, and a base pressure of 6×10 -7 Torr (approx. 8.0×10 -5 After confirming that the pressure had dropped to below 5×10 Pa, Ar gas was introduced at 10 sccm. The pressure was reduced to 5×10 by adjusting the opening of the valve connected to the exhaust system. -2 Torr (about 6.7 Pa), and then RF power of 1000 W was input and film formation was carried out for 15 minutes. The obtained Ir layer 25 had a thickness of 0.7 μm.

[0127] The thus obtained single crystal silicon substrate 23 on which the single crystal MgO layer 24 and the Ir layer 25 were laminated was used as the base 21 in Example 1.

[0128] Next, the substrate 21 was pretreated (bias treated) for diamond nucleation. The substrate was set on a flat electrode with a diameter of 15 mm, with the Ir layer 25 facing up. The base pressure was 1×10 -6 Torr (approx. 1.3×10 -4After confirming that the pressure had dropped below 100 Torr (approximately 1.3×10 Pa), 500 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced. The opening of the valve leading to the exhaust system was adjusted to reduce the pressure to 100 Torr (approximately 1.3×10 4 After that, a negative voltage was applied to the electrode on the substrate side, and the substrate surface was exposed to plasma for 90 seconds, thereby subjecting the substrate surface to a bias treatment.

[0129] Next, a diamond layer 26 was heteroepitaxially grown on the surface of the substrate by a direct current plasma CVD method. The bias-treated substrate 21 was set in the chamber of a direct current plasma CVD apparatus, and heated by a rotary pump for 10 -3 Torr (approx. 1.3×10 -1 After exhausting the gas to a base pressure of less than 1.5×10 Pa, 1000 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced as the source gas. The pressure in the chamber was adjusted to 110 Torr (approximately 1.5×10 4 After the pressure was adjusted to 1.0 Pa, a direct current of 2.0 A was applied to carry out film formation for 2 hours. The substrate temperature during film formation was measured with a pyrometer and found to be 950°C.

[0130] The obtained diamond layer 26 was a complete continuous film without peeling over the entire surface of the 10 mm diameter substrate, and had a film thickness of 10 μm. When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ=119.5° attributable to diamond (004) was 720 arcsec (approximately 0.2°).

[0131] Furthermore, the etch pit density was also evaluated. After the surface of the diamond layer 26 was plasma-treated using a 2.45 GHz microwave plasma CVD apparatus under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 hour, the etch pit density was measured by SEM observation and found to be 8×10 8 (cm -2 ) was.

[0132] Next, the diamond layer 26 was patterned. First, a 1000 nm SiO2 film 27 was formed on the diamond layer by RF plasma CVD using tetraethyl orthosilicate (TEOS) as a raw material (FIG. 4(b)). A resist pattern 28 was formed on the SiO2 film 27 (FIG. 4(c)). Next, a titanium (Ti) film and a gold (Au) film were formed in this order on the SiO2 film 27 on which the resist pattern 28 was formed, and then lifted off to form the SiO2 film 27 and the titanium (Ti) / gold (Au) pattern 29 in this order on the diamond layer 26 (FIG. 4(d)). Next, SiO2 etching was performed using CF4 gas to create a hard mask for diamond etching (FIG. 4(e)).

[0133] Next, the diamond layer was etched using an inductively coupled plasma etching apparatus under the conditions of 100 vol.% O2 gas, 2.0 Pa, 500 W, and 900 seconds (FIG. 4(f)). In this way, a pattern of diamond 22 was provided on the base surface (FIG. 3(A)).

[0134] At this time, the patterned diamond 22 in FIG. 3(A) is 50 μm square (i.e., W 21 The diamond pattern has rectangular dots with a spacing of 50 μm each. 22 The grooves were oriented in two directions perpendicular to each other, one of which was aligned with the

[0011] direction of the diamond layer.

[0135] Pattern gap depth D 21 is 10 μm, so the depth of the pattern gap D 21 and width W 22 Ratio of (D 21 / W 22 ) was 0.14. In addition, the bottom of the pattern gaps was in a state where the underlying Ir was exposed.

[0136] Next, the patterned diamond was cleaned by plasma treatment (Fig. 4(g)). Using an inductively coupled plasma etching device, the treatment was performed under the conditions of 100 vol.% CF4 gas, 2.0 Pa, 500 W, and 650 seconds. This operation successfully removed foreign matter, which was thought to be derived from Ir, that had adhered to the walls of the patterned diamond.

[0137] After cleaning, the SiO2 hard mask was removed with buffered hydrofluoric acid, and then the substrate was washed with hot mixed acid (Figure 4(h)).

[0138] Next, in the second step, diamonds 32 were grown from the patterned diamond 22 provided on the base surface into the pattern gaps 30 in the patterned diamond provided in the first step by microwave plasma CVD (Figure 3(B)).

[0139] The substrate on which the patterned diamond 22 was provided was set in the chamber of a microwave plasma CVD apparatus, and the rotary pump and turbo molecular pump were used to pump 7×10 -8 Torr (approx. 9.3×10 -6 After evacuating the chamber to 100 Pa, 500 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced as the source gas. The pressure in the chamber was adjusted to 110 Torr (approximately 1.5×10 4 After the pressure was adjusted to 1 Pa, a microwave power of 3000 W was applied to perform film formation for 18 hours. The substrate temperature during film formation was measured with a pyrometer and found to be 1035°C.

[0140] The resulting diamond layer had filled the gaps between the patterns. At this time, the thickness from the surface of the base to the surface of the substrate was 103 μm. When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ = 119.5° attributable to diamond (004) was 340 arcsec (approximately 0.1°).

[0141] Furthermore, the etch pit density was also evaluated. Using a 2.45 GHz microwave plasma CVD device, the surface of the diamond layer was plasma-treated under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 h. The etch pit density was then measured by SEM observation. The etch pit density was found to be 1×10 8 (cm -2 ), whereas in the gaps between the patterns, it was 3 × 10 6 (cm -2 ) and the etch pit density was reduced by about two orders of magnitude.

[0142] When the cross section of the substrate was observed with an SEM, a roughly triangular void with a cross section of 5 μm on a side was observed near the center of what had been a pattern gap, contacting the boundary between the Ir layer and the diamond layer.

[0143] To evaluate the stress in the diamond substrate, the change in warp on the back surface of the substrate before and after the formation of the diamond layer was measured using an optical interference or contact type measuring device. The measured value was then divided by the increase in film thickness before and after the formation of the diamond layer, and the calculated value was used as the evaluation value of the stress in the diamond substrate. The evaluation value here was 21×10 -2 It was.

[0144] Next, the surface of the obtained diamond substrate was polished. After polishing, the thickness from the base surface to the substrate surface was 71 μm, and the RMS surface roughness was 0.3 nm (measured by AFM, 10 μm square area).

[0145] Next, in the third step, the second diamond layer was patterned in the same manner as the first patterning, and a patterned diamond 33 was formed from the diamond 32 formed in the second step (FIG. 3(C)). The pattern shape here was a rectangular dot shape with a square of 50 μm (i.e., W 23 The pattern is made up of aligned diamonds with a spacing of 50 μm. 24The position of the pattern was shifted in parallel by 60 μm in the

[0011] direction of the diamond layer with respect to the first pattern.

[0146] That is, here, the diamond 32 formed in the second step is removed up to a position 10 μm from the boundary with the patterned diamond 22 provided in the first step.

[0147] Next, in the fourth step, diamond 36 was grown from the patterned diamond 33 into the patterned gaps 34 in the patterned diamond formed in the third step in the same manner as in the case of growing diamond from the patterned diamond provided on the base surface (FIG. 3(D)). The pattern gaps of the obtained diamond layer were filled. At this time, the thickness from the base surface to the substrate surface was 164 μm.

[0148] When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ=119.5°, which is attributed to diamond (004), was 340 arcsec (approximately 0.1°).

[0149] Furthermore, the etch pit density was also evaluated. Using a 2.45 GHz microwave plasma CVD device, the surface of the diamond layer was plasma-treated under conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 h. The etch pit density was then measured by SEM observation. It was found that the etch pit density was 3 × 10 both in the areas grown on the diamond pattern and in the gaps between the patterns. 6 (cm -2 ) and the etch pit density was low over the entire surface of the diamond substrate 37.

[0150] When the cross section of the manufactured diamond substrate 37 was observed using an SEM, a roughly triangular void with a side length of 5 μm was observed near the center of the area that had been the gap in the second pattern, abutting the boundary between the Ir layer and the diamond layer.

[0151] To evaluate the stress in the diamond substrate, the ratio (change in warp on the back surface of the substrate) / (increase in film thickness) was measured before and after the formation of the diamond layer. The value was 15×10 -2 It was.

[0152] Example 2 A diamond substrate was produced by the method shown in FIG.

[0153] First, as shown in Fig. 1(A), a pattern of diamonds 2 was provided on the surface of a base 1 (first step). Specifically, the pattern of diamonds 2 was provided through the steps shown in Fig. 2(a) to Fig. 2(f).

[0154] First, a heteroepitaxial diamond substrate (free-standing substrate) 6 having a diameter of 5.0 mm, a thickness of 0.5 mm, and a (100) surface that was polished on both sides was prepared, and was washed with hot mixed acid to form the base 1 (FIG. 2(a)).

[0155] Next, the patterning of the diamond substrate was performed in the same manner as in Example 1. First, a 1000 nm SiO2 film 7 was formed on the diamond layer by RF plasma CVD using tetraethyl orthosilicate (TEOS) as a raw material (FIG. 2(b)). A resist pattern 8 was formed on the SiO2 film 7 (FIG. 2(c)). Next, a titanium (Ti) film and a gold (Au) film were formed in order on the SiO2 film 7 on which the resist pattern 8 was formed, and then lifted off to form the SiO2 film 7 and the titanium (Ti) / gold (Au) pattern 9 in order on the diamond substrate 6 (FIG. 2(d)). Next, SiO2 etching was performed using CF4 gas to form a hard mask for diamond etching (FIG. 2(e)).

[0156] Next, the diamond layer was etched using an inductively coupled plasma etching apparatus under the conditions of 100 vol.% O2 gas, 2.0 Pa, 500 W, and 900 seconds (Fig. 2(f)). In this way, a pattern of diamond 2 was formed on the base surface (Fig. 1(A)).

[0157] At this time, the pattern shape in FIG. 1(A) is a rectangular dot shape of 50 μm square (i.e., W 11 The pattern is made up of aligned diamonds with a spacing of 50 μm. 12 The grooves were oriented in two directions perpendicular to each other, one of which was aligned with the

[0011] direction of the diamond layer.

[0158] Depth D of the pattern gap in the patterned diamond 2 11 Since the pattern gap depth D is set to 10 μm, 11 and width W 12 Ratio of (D 11 / W 12 ) was 0.14.

[0159] Next, the patterned diamond was cleaned by plasma treatment (Fig. 2(g)). Using an inductively coupled plasma etching device, the treatment was performed under the conditions of CF4 gas 100 vol.%, 2.0 Pa, 500 W, and 650 seconds.

[0160] After cleaning, the SiO2 hard mask was removed with buffered hydrofluoric acid, and then the substrate was washed with hot mixed acid (Figure 2(h)).

[0161] Next, in the second step, diamonds 12 were grown from the patterned diamond 2 provided on the base surface into the pattern gaps 10 in the patterned diamond provided in the first step by microwave plasma CVD (Figure 1(B)).

[0162] The substrate with the patterned diamond 2 was placed in the chamber of a microwave plasma CVD apparatus, and the rotary pump and turbo molecular pump were used to pump 7×10 -8 Torr (approx. 9.3×10 -6After evacuating the chamber to 100 Pa, 500 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced as the source gas. The pressure in the chamber was adjusted to 110 Torr (approximately 1.5×10 4 After the pressure was adjusted to 1 Pa, a microwave power of 3000 W was applied to perform film formation for 15 hours. The substrate temperature during film formation was measured with a pyrometer and found to be 1050°C.

[0163] The resulting diamond layer had filled the gaps between the patterns. At this time, the thickness from the surface of the base to the surface of the substrate was 78 μm. When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ = 119.5° attributable to diamond (004) was 340 arcsec (approximately 0.1°).

[0164] Furthermore, the etch pit density was also evaluated. Using a 2.45 GHz microwave plasma CVD device, the surface of the diamond layer was plasma-treated under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 h. The etch pit density was then measured by SEM observation. The etch pit density was found to be 2 × 10 in the area grown on the patterned diamond. 8 (cm -2 ), whereas in the gaps between the patterns, it was 4×10 6 (cm -2 ) and the etch pit density was reduced by about two orders of magnitude.

[0165] When the cross section of the substrate was observed using an SEM, it was found that the gaps between the patterns had been completely filled.

[0166] To evaluate the stress in the diamond substrate, the ratio (change in warp on the back surface of the substrate) / (increase in film thickness) was measured before and after the formation of the diamond layer. The value was 15×10 -2 It was.

[0167] Next, the surface of the obtained diamond substrate was polished. After polishing, the thickness from the base surface to the substrate surface was 56 μm, and the RMS surface roughness was 0.3 nm (measured by AFM, 10 μm square area).

[0168] Next, in the third step, the second diamond layer was patterned in the same manner as the first patterning, and a patterned diamond 13 was formed from the diamond formed in the second step (FIG. 1(C)). The pattern shape here was a rectangular dot shape of 50 μm square (i.e., W 13 The pattern is made up of aligned diamonds with a spacing of 50 μm. 14 The distance between the diamond layer and the pattern was set to 70 μm. However, the position of the pattern was shifted 60 μm in parallel in the

[0011] direction of the diamond layer with respect to the first pattern. In other words, the diamond formed in the second process was removed up to a position 10 μm from the boundary with the patterned diamond formed in the first process.

[0169] Next, in the fourth step, diamond 16 was grown from patterned diamond 13 in the same manner as in the case of growing diamond from the patterned diamond on the base surface (Fig. 1(D)). The resulting diamond layer had the gaps between the patterns filled. At this time, the thickness from the base surface to the substrate surface was 134 μm.

[0170] When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ=119.5°, which is attributed to diamond (004), was 340 arcsec (approximately 0.1°).

[0171] Furthermore, the etch pit density was also evaluated. Using a 2.45 GHz microwave plasma CVD device, the surface of the diamond layer was plasma-treated under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 h. The etch pit density was then measured by SEM observation. The etch pit density was found to be 3 × 10 in the area grown on the patterned diamond. 6 (cm -2 ), the gaps between the patterns are also 4×10 6 (cm -2 ), the etch pit density was low over the entire diamond substrate surface.

[0172] When the cross section of the obtained diamond substrate 17 was observed by SEM, it was found that the gaps between the patterns had been completely filled.

[0173] To evaluate the stress in the diamond substrate, the ratio (change in warp on the back surface of the substrate) / (increase in film thickness) was measured before and after the formation of the diamond layer. The value was 10×10 -2 It was.

[0174] Comparative Example 1 First, a single crystal silicon (Si) substrate was prepared, the diameter of which was 10.0 mm, the thickness of which was 1.0 mm, and the surface of which was the (100) plane and was polished on both sides.

[0175] A layer of single-crystal MgO was formed on one side of the prepared single-crystal silicon substrate by electron beam evaporation. At this time, the conditions were a substrate temperature of 900°C in a vacuum, and epitaxial growth was allowed until the single-crystal MgO layer was 1 μm thick. Furthermore, a layer of Ir was formed on this single-crystal MgO layer. To form the Ir layer, radio frequency (RF) magnetron sputtering (13.56 MHz) was used with an Ir target having a diameter of 6 inches (150 mm), a thickness of 5.0 mm, and a purity of 99.9% or higher. The substrate on which the single-crystal MgO layer had been formed was heated to 800°C, and a base pressure of 6×10 -7 Torr (approx. 8.0×10 -5 After confirming that the pressure had dropped to below 5×10 Pa, Ar gas was introduced at 10 sccm. The pressure was reduced to 5×10 by adjusting the opening of the valve connected to the exhaust system. -2Torr (approximately 6.7 Pa) was then set, and film formation was carried out for 15 minutes by inputting an RF power of 1000 W. The obtained Ir layer had a thickness of 0.7 μm.

[0176] The thus obtained single crystal silicon substrate on which a single crystal MgO layer and an Ir layer were laminated was used as a base in Comparative Example 1.

[0177] Next, the substrate was pretreated (bias treated) for diamond nucleation. The substrate was placed on a flat electrode with a diameter of 15 mm, with the Ir layer facing up. The base pressure was 1×10 -6 Torr (approx. 1.3×10 -4 After confirming that the pressure had dropped below 100 Torr (approximately 1.3×10 Pa), 500 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced. The opening of the valve leading to the exhaust system was adjusted to reduce the pressure to 100 Torr (approximately 1.3×10 4 After that, a negative voltage was applied to the electrode on the substrate side, and the substrate surface was exposed to plasma for 90 seconds to perform a bias treatment.

[0178] Next, a diamond layer was heteroepitaxially grown on the surface of the substrate by DC plasma CVD. The bias-treated substrate was set in the chamber of a DC plasma CVD apparatus and heated with a rotary pump for 10 -3 Torr (approx. 1.3×10 -1 After exhausting the gas to a base pressure of less than 1.5×10 Pa, 1000 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced as the source gas. The pressure in the chamber was adjusted to 110 Torr (approximately 1.5×10 4 After the pressure was adjusted to 1.0 Pa, a direct current of 2.0 A was applied to carry out film formation for 2 hours. The substrate temperature during film formation was measured with a pyrometer and found to be 950°C.

[0179] The obtained diamond layer was a complete continuous film without peeling over the entire surface of the 10 mm diameter substrate, and had a film thickness of 10 μm. When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ = 119.5° attributable to diamond (004) was 720 arcsec (approximately 0.2°).

[0180] Furthermore, the etch pit density was also evaluated. The surface of the diamond layer was plasma-treated using a 2.45 GHz microwave plasma CVD device under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 hour. The etch pit density was then measured by SEM observation, and was found to be 8 × 10 8 (cm -2 ) was.

[0181] Next, the substrate on which the diamond nuclei were formed was placed in the chamber of a microwave plasma CVD apparatus, and the substrate was heated to 7 × 10 -8 Torr (approx. 9.3×10 -6 After evacuating the chamber to 100 Pa, 500 sccm of hydrogen-diluted methane (CH4 / (CH4+H2)=5.0 vol.%) was introduced as the source gas. The pressure in the chamber was adjusted to 110 Torr (approximately 1.5×10 4 After the pressure was adjusted to 1 Pa, a microwave power of 3000 W was applied to perform film formation for 18 hours. The substrate temperature during film formation was measured with a pyrometer and found to be 1035°C.

[0182] The obtained diamond layer was a complete continuous film without peeling over the entire surface of the 10 mm diameter substrate, and had a film thickness of 90 μm. When this diamond layer was subjected to X-ray diffraction measurement (incident X-ray wavelength 1.54 Å), the rocking curve half-width of the diffraction intensity peak at 2θ = 119.5° attributable to diamond (004) was 720 arcsec (approximately 0.2°).

[0183] Furthermore, the etch pit density was also evaluated. The surface of the diamond layer was plasma-treated using a 2.45 GHz microwave plasma CVD device under the conditions of 100 vol.% H2 gas, 0.8 Pa, 2200 W, and 1 hour. The etch pit density was then measured by SEM observation, and the value was 4 × 10 8 (cm -2 ) was.

[0184] To evaluate the stress in the diamond substrate, the ratio (change in warp on the back surface of the substrate) / (increase in film thickness) was measured before and after the formation of the diamond layer, and the value was 67×10 -2 It was.

[0185] From the above results, it is found that if a diamond substrate is manufactured by the method for manufacturing a diamond substrate of the present invention, a high-quality diamond substrate with sufficiently few defects and small stress can be obtained. It is also found that the diamond substrate of the present invention has sufficiently few defects and reduced stress.

[0186] The present invention is not limited to the above-mentioned embodiment. The above-mentioned embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0187] 1,21...base, 2,22...patterned diamond formed in the first step, 3...diamond, 23...silicon (Si) substrate, 24...intermediate layer (single crystal MgO layer), 25...surface layer (Ir layer), 6...heteroepitaxial diamond substrate, 26...diamond layer, 7,27...SiO2 film, 8,28...resist pattern, 9,29...titanium (Ti) / gold (Au) pattern, 10,30...pattern gap in the patterned diamond formed in the first step, 11,31...bottom of the pattern gap in the patterned diamond formed in the first step, 12,32...diamond formed in the second step, 13,33...patterned diamond formed in the third step, 14,34...pattern gap in the patterned diamond formed in the third step, 15,35...bottom of the pattern gap in the patterned diamond formed in the third step, 16,36...Diamond formed in the fourth step, 17,37,100...Diamond substrate, 50...Base, 51...Diamond layer, 52...Void, 101...Surface.

Claims

[Claim 1] A diamond substrate comprising a base and a diamond layer formed on a surface of the base, the surface of the substrate is a different material other than diamond; A diamond substrate, characterized in that the entire surface of the diamond layer is composed of at least one of laterally grown diamond and diamond grown from the laterally grown diamond.

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