Diamond film

Abstract

Provided is an oriented polycrystalline diamond film that can be provided at low cost and is suitable for achieving an increased size. This diamond film is composed of oriented polycrystalline diamond. The oriented polycrystalline diamond includes a plurality of diamond single-crystal particles having a single-crystal structure in a direction substantially normal to the surface of the diamond film.

Description

Diamond film

[0001] The present disclosure relates to a diamond film.

[0002] Diamond is a material having an extremely high thermal conductivity (approximately 22 W / cm·K), and is expected to be applied to heat spreaders for semiconductor devices and the like. Applications such as heat spreaders require a diamond film or substrate of a certain size.

[0003] As a method for producing a diamond substrate, Non-Patent Document 1 (Makoto Kasu, Ryota Takaya, and Seong-Woo Kim, Diamond & Related Materials 126 (2022) 109086) discloses that after forming a 1 μm-thick Ir buffer layer on a sapphire substrate by sputtering, diamond nuclei are formed on the Ir buffer layer by a bias-enhanced nucleation (BEN) process using a direct current plasma CVD apparatus, and then a diamond layer is grown on the BEN-treated Ir buffer layer by microwave plasma CVD, thereby producing a sapphire / Ir buffer layer / diamond layer laminate. This document also describes that a microneedle process is essential to obtain a free-standing diamond layer without breakage from the laminate.

[0004] Makoto Kasu, Ryota Takaya, and Seong-Woo Kim, "Growth of high-quality inch-diameter heteroepitaxial diamond layers on sapphire substrates in comparison to MgO substrates", Diamond & Related Materials 126 (2022) 109086

[0005] Self-supporting diamond single-crystal substrates are difficult to manufacture in large quantities and are very expensive. Similarly, self-supporting polycrystalline diamond substrates are also costly. Therefore, there is a need for inexpensive alternatives to diamond single-crystal and polycrystalline self-supporting substrates.

[0006] The present inventors have now discovered that by constructing the diamond film from oriented polycrystalline diamond having a predetermined crystal structure, it is possible to provide an oriented polycrystalline diamond film that can be supplied at low cost and is also suitable for scaling up to large sizes.

[0007] Therefore, the object of the present invention is to provide an oriented polycrystalline diamond film that can be supplied at low cost and is also suitable for scaling up to large sizes.

[0008] The following embodiments are provided according to this disclosure: [Embodiment 1] A diamond film composed of oriented polycrystalline diamond, wherein the oriented polycrystalline diamond includes a plurality of diamond single crystal particles having a single crystal structure in a direction substantially normal to the surface of the diamond film. [Embodiment 2] The diamond film according to Embodiment 1, wherein the diamond film is (100) plane oriented. [Embodiment 3] The peak intensity of the (111) plane measured by X-ray diffraction (XRD) on the surface of the diamond film. １ Peak intensity I of the (400) plane relative to ２ Ratio I ２ / I １A diamond film according to Embodiment 1 or 2, wherein the ratio is 5.5 or higher. [Embodiment 4] A diamond film according to any one of Embodiments 1 to 3, wherein the (100) crystal orientation of each diamond single crystal particle measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD) is distributed tilted at various tilt angles from a reference (100) crystal orientation, and the average tilt angle is 0.5 to 10°. [Embodiment 5] A diamond film according to Embodiment 4, wherein 80% or more of the diamond single crystal particles measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD) have a tilt angle in the range of 0.5 to 10°. [Embodiment 6] A diamond film according to any one of Embodiments 1 to 5, wherein the diamond single crystal particles have crystal orientations that are generally aligned in the in-plane direction of the diamond film. [Aspect 7] The diamond film according to any one of aspects 1 to 6, wherein the (110) crystal orientation of each diamond single crystal particle, measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD), is distributed rotated at various twist angles from a reference (110) crystal orientation, and the average twist angle is 0.5 to 15°. [Aspect 8] The diamond film according to aspect 7, wherein 80% or more of the diamond single crystal particles measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD) have a twist angle in the range of 0.5 to 15°. [Aspect 9] The diamond film according to any one of aspects 1 to 8, wherein when measured on a cross-section of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD), the diamond single crystal particles constituting the oriented polycrystalline diamond include a plurality of anisotropic particles that have grown in a direction away from the back surface of the diamond film, and 50% or more of the area of ​​the plurality of anisotropic particles is interrupted in the region near the back surface up to a depth of 20 μm from the back surface of the diamond film. [Aspect 10] The diamond film according to any one of aspects 1 to 9, wherein the surface of the diamond film has an arithmetic mean roughness Ra of 0.6 nm or less.[Aspect 11] The diamond film according to any one of Aspects 1 to 10, wherein the diamond single crystal particles exposed on a surface of the diamond film communicate with a back surface of the diamond film without interposing a grain boundary. [Aspect 12] The diamond film according to any one of Aspects 1 to 11, wherein the diamond film has a thickness of 30 µm or more. [Aspect 13] The cross-sectional average diameter D at the outermost surface of diamond single crystal particles exposed on the surface of the diamond film. Ｔ an aspect ratio defined as a ratio of the thickness T of the diamond film to T / D Ｔ The diamond film according to any one of Aspects 1 to 12, wherein is 1.0 or more. [Aspect 14] The cross-sectional average diameter D at the outermost surface of diamond single crystal particles on the back surface of the diamond film Ｂ to the cross-sectional average diameter D at the outermost surface of diamond single crystal particles exposed on the surface of the diamond film Ｔ a ratio D Ｔ / D Ｂ The diamond film according to any one of Aspects 1 to 13, wherein is greater than 1.0. [Aspect 15] The diamond film has 19.625 cm ２ The diamond film according to any one of Aspects 1 to 14, having an area of not less than that. [Aspect 16] The diamond film according to any one of Aspects 1 to 15, wherein the diamond single crystal particles are doped with an n-type dopant or a p-type dopant.

[0009] It is a schematic cross-sectional view conceptually showing the diamond film of the present disclosure. It is a diagram showing ICDD Card #01-071-3649. The cross-sectional average diameter D on the front surface and back surface of the diamond film of the present disclosure Ｔ and D ＢThis is a schematic cross-sectional view to explain the calculation. This is an SEM image of the surface of the diamond film fabricated in Example 1. These are pole figures of {001} and {110} related to angle adjustment for obtaining the inverse pole figure orientation mapping in Example 1. This is the inverse pole figure orientation mapping of the surface of the diamond film measured in Example 1. This is a mapping image of the tilt angle distribution of the surface of the diamond film measured in the same field of view as Figure 5B. This is a histogram showing the frequency of tilt angles of diamond single crystal particles on the surface of the diamond film, calculated from the tilt angle distribution mapping in Figure 5C. This is the inverse pole figure orientation mapping of the cross section of the diamond film measured in Example 1. This is a band contrast diagram based on the inverse pole figure orientation mapping in Figure 6A. This is a mapping image of the tilt angle distribution of the cross section of the diamond film measured in the same field of view as Figure 6B. This is a histogram showing the frequency of tilt angles of diamond single crystal particles on the cross section of the diamond film, calculated from the tilt angle distribution mapping in Figure 6C.

[0010] Figure 1 conceptually shows the diamond film 10 of this disclosure. The diamond film 10 is a film composed of oriented polycrystalline diamond. This oriented polycrystalline diamond contains a plurality of diamond single crystal particles 10a, and these diamond single crystal particles 10a have a single crystal structure in a direction approximately normal to the surface 10b of the diamond film 10. That is, the diamond film 10 is composed of a plurality of diamond single crystal particles 10a (typically columnar particles) linked two-dimensionally in the horizontal plane, and therefore has a single crystal structure in the direction approximately normal to the surface. Thus, although the diamond film 10 as a whole is not a single crystal, it has a single crystal structure at the local domain level, and can therefore have high crystallinity sufficient to ensure device characteristics. However, the diamond film 10 of this disclosure is not a diamond single crystal film, much less a diamond single crystal self-supporting substrate. As mentioned above, self-supporting diamond single crystal substrates are difficult to manufacture in large sizes and are very expensive. Also, even diamond polycrystalline self-supporting substrates are expensive. To address these problems, by adopting a film form as the diamond product (it does not need to be in the form of a self-supporting substrate) as described above, and by constructing the film with oriented polycrystalline diamond having a predetermined crystal structure, it is possible to provide an oriented polycrystalline diamond film 10 that can be supplied at low cost and is also suitable for scaling up. In other words, the diamond film 10 of this disclosure can be manufactured inexpensively on a substrate 12 such as a silicon substrate, and moreover, by using a large Si substrate or the like as the substrate 12, it is easy to scale up the diamond film 10. Therefore, the diamond film 10 of this disclosure can be used as an inexpensive alternative to diamond single crystal substrates and diamond polycrystalline self-supporting substrates. Furthermore, since the diamond film 10 of this disclosure is an oriented polycrystalline diamond film, it also has the advantage of improved thermal conductivity and polishability compared to random polycrystalline diamond films. Therefore, the diamond film 10 is particularly advantageous for applications that diffuse heat in the direction of the film surface (especially heat spreaders for semiconductor devices).

[0011] As described above, the diamond film 10 is composed of oriented polycrystalline diamond, and the oriented polycrystalline diamond contains a plurality of diamond single crystal particles 10a having a single crystal structure in a direction approximately normal to the surface 10b of the diamond film 10. Therefore, the diamond single crystal particles 10a exposed on the surface of the diamond film 10 are typically in communication with the back surface of the diamond film 10 without grain boundaries. The presence of grain boundaries is a factor that reduces the thermal conductivity in the thickness direction, but with this configuration, such a reduction in thermal conductivity can be avoided. The diamond single crystal particles 10a are typically columnar particles, and more typically prismatic particles. The top view shape or cross-sectional shape of the prismatic particles is typically a quadrilateral, or a polygon formed by the fusion of multiple quadrilaterals.

[0012] The diamond film 10 is preferably (100) plane oriented. Although diamond is known as a hard material, the (100) plane of diamond is relatively easy to polish compared to other planes such as the (110) plane and the (111) plane, which is advantageous when polishing the surface 10b of the diamond film 10 to form a flat surface. The (100) plane orientation can be confirmed by analyzing the surface 10b of the diamond film 10 with an electron backscatter diffraction (EBSD) and obtaining an inverse pole figure orientation mapping. Since diamond is an isotropic crystal, the (100) plane is equivalent to the (001) plane and the (010) plane. Therefore, the evaluation of the (100) plane orientation can be substituted by evaluating the (001) plane orientation or the (010) plane orientation of the diamond film 10 with EBSD.

[0013] The degree of (100) plane orientation in the diamond film 10 is preferably evaluated by comparing the peak intensity of the (400) plane, which is equivalent to the (100) plane, with the peak intensity of the (111) plane using X-ray diffraction (XRD). In this specification, "peak intensity" means maximum intensity (peak height). When measuring diamond with XRD, as shown in the information on ICDD card #01-071-3649 in Figure 2, the crystal plane with the strongest diffraction intensity is the (111) plane, and the (400) plane has a relatively weak intensity. Therefore, the peak intensity of the (111) plane measured by X-ray diffraction (XRD) for the surface 10b of the diamond film 10 is １ Peak intensity I of the (400) plane relative to ２ Ratio I ２ / I １ However, it is preferably 5.5 or higher, more preferably 10 or higher, and even more preferably 25 or higher. Within these ranges, it is possible to provide a diamond film 10 that is highly oriented to a (100) plane equivalent to a (400) plane. Peak intensity ratio I ２ / I １ Since a higher value is always better, there should be no particular upper limit, but typically it is 100 or less, and more typically 50 or less.

[0014] The (100) crystal orientation of each diamond single crystal particle 10a, measured on the surface 10b of the diamond film 10 by inverse pole figure mapping using electron beam backscatter diffraction (EBSD), is distributed tilted at various tilt angles from a reference (100) crystal orientation. A small average tilt angle is desirable, preferably 10° or less, more preferably 5.0° or less, even more preferably 2.5° or less, and particularly preferably 1.0° or less. Such a tilt angle has the advantage of aligning the crystal orientation of the polished surface and shortening the polishing time when polishing the film surface. From the viewpoint of shortening the polishing time, there should be no lower limit on the average tilt angle, but typically the average tilt angle is 0.5° or more. The reference (100) crystal orientation is identified as pointing to the (100) axis, which coincides with the direction normal to the film surface of the diamond film 10. As mentioned above, in diamond, the (100) plane is equivalent to the (001) plane and the (010) plane. Therefore, the evaluation of the (100) plane orientation can be substituted by evaluating the (001) plane orientation or the (010) plane orientation of the diamond film 10 using EBSD. Furthermore, it is preferable that 80% or more of the diamond single crystal grains 10a measured by EBSD inverse pole figure mapping on the surface 10b of the diamond film 10 have a tilt angle within the range of 0.5 to 10°, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more have a tilt angle within the above range. Such a tilt angle distribution has the advantage that the crystal orientation of the polished surface is aligned, and the time required for polishing is shortened.

[0015] It is preferable that the diamond single crystal particles 10a have a crystal orientation that is generally aligned in the in-plane direction of the diamond film 10. In this case, the diamond film 10 can be said to be a biaxially oriented film having a crystal orientation that is generally aligned not only in the approximate normal direction but also in the in-plane direction, particularly in the rotational direction (hereinafter referred to as the twist direction) centered on a normal oriented approximately perpendicular to the film surface of the diamond film 10. Specifically, the (110) crystal orientation of each diamond single crystal particle measured by EBSD inverse pole figure mapping on the surface 10b of the diamond film 10 is distributed rotated at various twist angles (in the twist direction) from a reference (110) crystal orientation, and it is desirable that the average twist angle be small, preferably 15° or less, more preferably 5° or less, even more preferably 2.5° or less, and particularly preferably 1.0° or less. Such an average twist angle has the advantage that the crystal orientation of the polished surface is aligned, and the time required for polishing is shortened. From the perspective of reducing polishing time, there should be no lower limit on the average twist angle, but typically the average twist angle is 0.5° or greater. There are no particular limitations on the method for determining the average twist angle, but it can be determined using methods such as EBSD or the euhedron of oriented single crystal grains.

[0016] The following describes a method for determining the average twist angle from the euhedron of oriented single crystal grains. (100) oriented diamond grains have a square crystal shape, and the sides of this square are in the (110) crystal orientation. Therefore, a straight line L is drawn in the plane of the observation image (e.g., SEM image), and the average value A of the angles between line L and the sides of the square of each oriented single crystal grain is calculated. Next, a straight line L' is drawn from line L at an angle A. The absolute value of the angle between this line L' and the sides of the square of each oriented single crystal grain is the twist angle. The average twist angle is calculated from the twist angles of multiple oriented single crystal grains. Alternatively, by using EBSD, the average twist angle can also be determined by using the direction that most frequently shows the (110) crystal orientation as the reference line.

[0017] Furthermore, it is preferable that 80% or more of the diamond single crystal particles 10a, measured by EBSD inverse pole figure mapping on the surface 10b of the diamond film 10, have a twist angle in the range of 0.5 to 15°, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more have a twist angle within the above range. Such a twist angle distribution has the advantage that the crystal orientation of the polished surface is aligned, and the time required for polishing is shortened.

[0018] When measured by EBSD inverse pole figure mapping on the cross-section of the diamond film 10, the diamond single crystal particles constituting the oriented polycrystalline diamond may contain a plurality of anisotropic particles that have grown in a direction away from the back surface 10c of the diamond film 10. Here, anisotropic particles are defined as particles whose tilt angle of the (100) axis is shifted by 20° or more. In this case, it is preferable that 50% or more, more preferably 80% or more, and even more preferably 90% or more of the plurality of anisotropic particles are interrupted in the region near the back surface up to a depth of 20 μm from the back surface 10c of the diamond film 10, based on area. With such a configuration, the exposure of anisotropic particles on the surface 10b of the diamond film 10 can be eliminated or reduced, and the crystal orientation on the surface 10b can be improved.

[0019] The diamond film 10 of this disclosure easily achieves a high degree of smoothness on its surface 10b. One reason for this is that, while diamond has different growth rates depending on its crystal orientation, the diamond film 10 is an oriented polycrystalline diamond film. As a result, each diamond single crystal particle 10a grows at a more uniform rate than in a random polycrystalline diamond film, making it easier for the upper surfaces of the diamond single crystal particles 10a exposed on the surface 10b to be aligned. Another reason is that, because it is an oriented polycrystalline diamond film, it has improved polishability compared to a random polycrystalline diamond film, and this tendency is particularly applicable in the case of (100) plane orientation. Specifically, the surface 10b of the diamond film 10 preferably has an arithmetic mean roughness Ra of 5 nm or less, more preferably 1 nm or less, and even more preferably 0.6 nm or less. The lower limit of the arithmetic mean roughness Ra of the surface 10b is not particularly limited, but is typically 0.1 nm or more. The arithmetic mean roughness Ra can be measured in accordance with JIS B 0601 (2001).

[0020] The thickness T of the diamond film 10 is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 5 μm or more, particularly preferably 10 μm or more, and most preferably 30 μm or more, for example 50 μm or more, 70 μm or more, or 100 μm or more. Therefore, there should be no upper limit specified for the thickness T of the diamond film 10. On the other hand, from the viewpoint of manufacturing cost, a thickness T of 70 μm or less is practical for the diamond film 10, and 50 μm or less is preferable.

[0021] The average cross-sectional diameter D at the outermost surface of the diamond single crystal grains 10a on the back surface 10c of the diamond film 10. Ｂ The average cross-sectional diameter D at the outermost surface of the diamond single crystal grains 10a exposed on the surface 10b of the diamond film 10. Ｔ Ratio D Ｔ / D Ｂ It is preferable that it is greater than 1.0, more preferably 5.0 or higher, even more preferably 10 or higher, and particularly preferably 20 or higher. Within this range, there is the advantage that the thermal conductivity in the thickness direction and the polishability are improved. On the other hand, in terms of thermal conductivity in the in-plane direction of the film, D Ｔ / DＢ A smaller value is preferable, more preferably 100 or less, even more preferably 80 or less, particularly preferably 60 or less, and most preferably 20 or less. D that balances thermal conductivity in the film surface and thermal conductivity in the film thickness direction. Ｔ / D Ｂ The preferred range is 5.0 to 100, more preferably 10 to 80, and even more preferably 20 to 60. Average cross-sectional diameter D Ｔ and the average cross-sectional diameter D Ｂ This can be determined using a band contrast diagram based on the inverse pole figure orientation mapping of the cross-section of the diamond film 10, as illustrated in Figure 3. That is, a straight line S parallel to the substrate 12 or back surface 10c is located at a predetermined distance (e.g., 3 μm) below the surface 10b (outermost surface) of the diamond film 10, as shown in Figure 3. Ｔ Draw a line S. Ｔ Let n be the number of intersection points X between the diamond film 10 and the grain boundaries, and let L be the distance between intersection points X that contain at least 10 intersection points X. Ｔ Defined as, D Ｔ = L Ｔ The value calculated by the formula / (n-1) represents the average cross-sectional diameter D of the diamond single crystal grains 10a on the surface 10b of the diamond film 10. Ｔ This can then be determined. Similarly, a straight line S parallel to the substrate 12 or the back surface 10c, as shown in Figure 3, is located at a predetermined distance (e.g., 3 μm) above the back surface 10c of the diamond film 10 (e.g., the interface between the substrate 12 and the diamond film 10). Ｂ Draw a line S. Ｂ Let n be the number of intersection points X between the diamond film 10 and the grain boundaries, and let L be the distance between intersection points X that contain at least 10 intersection points X. Ｂ Defined as, D Ｂ = L Ｂ The value calculated by the formula / (n-1) is the average cross-sectional diameter of the diamond single crystal grains 10a on the back surface 10c of the diamond film 10, D Ｂ That should be the decision.

[0022] The average cross-sectional diameter D at the outermost surface of the diamond single crystal grains 10a exposed on the surface 10b of the diamond film 10. Ｔ The aspect ratio T / D is defined as the ratio of the thickness T of the diamond film 10 to the ratio of the thickness T of the diamond film 10.Ｔ A larger T / D ratio is preferable because it improves abrasiveness. From this perspective, Ｔ The ratio is preferably 5 or more, more preferably 10 or more, even more preferably 30 or more, and particularly preferably 100 or more. On the other hand, the aspect ratio T / D Ｔ If the ratio is too large, the thermal conductivity within the film surface may decrease. Therefore, T / D Ｔ The T / D ratio is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less. Ｔ A preferred range is 5 to 100, and more preferably 10 to 50.

[0023] The area of ​​the diamond film 10 is 19.625 cm². ２ Preferably, it is greater than or equal to the area of ​​a circle with a diameter of 5 cm (approximately 2 inches), and more preferably 78.540 cm². ２ (corresponding to a circular area of ​​10 cm (approximately 4 inches) or larger in diameter), more preferably 176.715 cm². ２ This corresponds to a circular area of ​​150 cm (approximately 6 inches) or more in diameter. Therefore, when the plan view shape of the diamond film 10 is circular or includes a circular portion, the diameter of the diamond film 10 is preferably 5 cm or more, more preferably 10 cm or more, and even more preferably 15 cm or more. However, the plan view shape of the diamond film 10 does not have to be circular or include a circular portion. In any case, the larger the area of ​​the diamond film 10, the more useful it is as a heat spreader, so there should be no upper limit on its area, but from the viewpoint of manufacturing cost, the area of ​​the diamond film 10 is 314.16 cm². ２ The following (corresponding to a circular area with a diameter of 200 cm (approximately 8 inches) or less) is considered realistic.

[0024] The diamond single crystal particles 10a may be doped with an n-type dopant or a p-type dopant. In this case, the diamond film 10 can be used as a component or layer such as a p-type electrode, an n-type electrode, a p-type layer, or an n-type layer.

[0025] The diamond film 10 of this disclosure can be formed by first performing a bias-enhanced nucleation (BEN) process (hereinafter referred to as bias treatment) as a pretreatment for forming diamond nuclei on a substrate 12 such as a Si single crystal substrate, and then depositing the diamond film 10 by known film deposition methods such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). Preferably, a (100) oriented, double-sided polished Si single crystal substrate with no off-angle is used as the substrate 12. The pretreatment for forming diamond nuclei can preferably be carried out by setting the substrate 12 in a bias treatment device, evacuating the vacuum, heating the substrate 12 to a temperature of 800 to 1100°C, and performing bias treatment at a pressure of 50 to 200 Torr in the presence of hydrogen-diluted methane gas. The diamond film 10 can preferably be formed by heteroepitaxial growth of the diamond film 10 on the bias-treated side of the substrate 12 at 800 to 1100°C for 2 to 40 hours using microwave plasma CVD.

[0026] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0027] Example 1 (1) Fabrication of a diamond film A double-sided polished Si single crystal substrate with a diameter of 50.8 mm and a thickness of 1 mm, oriented in a (100) plane and without off-angle, was prepared as a substrate for diamond film deposition. This Si single crystal substrate was subjected to pretreatment such as bias treatment to form diamond nuclei. Specifically, the Si single crystal substrate was set on the negative voltage application electrode (cathode) of a bias treatment device and evacuated. Next, the Si single crystal substrate was heated to 800°C, and then 3 vol% hydrogen-diluted methane gas was introduced to set the pressure to 130 Torr and perform bias treatment. This bias treatment was performed by applying a DC voltage between the two electrodes and passing a predetermined DC current. Finally, a diamond film was obtained by heteroepitaxial growth of a diamond film on the bias-treated side of the Si single crystal substrate at 1000°C for 8 hours using microwave plasma CVD.

[0028] (2) Analysis of the diamond film The following various analyses were performed on the prepared diamond film.

[0029] (2a) Surface SEM When the surface of the diamond film was observed using a SEM (SU-5000, manufactured by Hitachi High-Technologies Corporation), the SEM image shown in Figure 4 was obtained. As shown in Figure 4, the square outlines of the diamond single crystal grains were observed to be arranged in a row. In addition to squares, diamond single crystal grains that were formed by the fusion of multiple squares into polygons were also observed. In the obtained SEM image (magnification: 1000x, field of view: 127 μm × 89 μm), the bright linear parts were considered to be the edges representing the outlines of the diamond single crystal grains, and the length of each edge was measured and the average value was calculated to be 7.4 μm.

[0030] (2b) Surface EBSD An electron backscatter diffraction (EBSD) spectrometer (Nordlys Nano, Oxford Instruments) was attached to a SEM (SU-5000, Hitachi High-Technologies Corporation) to perform inverse pole figure orientation mapping of the surface of a diamond film in a field of view of 797 μm × 1061 μm. The conditions for this EBSD measurement were as follows: <EBSD Measurement Conditions> - Acceleration voltage: 15 kV - Spot intensity: 70 - Working distance: 22.5 mm - Step size: 0.5 μm - Sample tilt angle: 70° - Measurement program: Aztec (version 3.3)

[0031] To adjust for the sample displacement between measurements, the angles of the pole diagrams {001} and {110} were adjusted as shown in Figure 5A to obtain the inverse pole diagram orientation mapping shown in Figure 5B. This angle adjustment was performed so that the point was located at the center in the pole diagram {001} and the four points were symmetrical in the pole diagram {110}, as shown in Figure 5A. From the inverse pole diagram orientation mapping obtained by adjusting the angles of the pole diagrams {001} and {110} in this way, it was found that the diamond film is a biaxially oriented polycrystalline film that is oriented along the (100) axis in a direction approximately normal to the surface of the film, as well as in the in-plane direction of the film.

[0032] Figures 5C and 5D show a mapping image of the tilt angle distribution from the (100) axis on the surface of the diamond film in the same field of view as described above, and the frequency distribution (histogram) of the tilt angle of the diamond single crystal particles from the (100) axis in the said mapping image, respectively. The average tilt angle of the diamond single crystal particles from the (100) axis was 5.0°, and the tilt angle distribution approximated a Gaussian distribution. The average tilt angle was calculated by loading the measurement results from EBSD into the results analysis software HKL CHANNEL 5 (Oxford Instruments) as the Diamond space group m3m, adjusting the plot in the analysis application Mambo included with HKL CHANNEL 5 so that it is four times symmetric to the center of the pole figure {001} as shown in Figure 5A, and then quantifying the 100-axis displacement (tilt angle) in the analysis application Tango included with HKL CHANNEL 5 and calculating the average value. Furthermore, the proportion (frequency) of diamond single crystal grains with a tilt angle of 0.5 to 10° was 92%.

[0033] Each diamond single crystal particle constituting the diamond film is oriented in the in-plane direction (horizontal direction) parallel to the film surface of the diamond film. The average twist angle of the diamond single crystal particles with respect to the (110) axis is 4.5°, and the twist angle distribution approximates a Gaussian distribution. This average twist angle was obtained by loading the measurement results from EBSD into the results analysis software HKL CHANNEL 5 (Oxford Instruments) as the Diamond space group m3m, adjusting the plot in the analysis application Mambo included with HKL CHANNEL 5 so that it is four times symmetric to the center of the pole figure {001} as shown in Figure 5A, and then quantifying the deviation (twist angle) in the 110 axis direction using the analysis application Tango included with HKL CHANNEL 5 and calculating the average value. Furthermore, the proportion (frequency) of diamond single crystal grains with a twist angle of 0.5 to 15° was 96%.

[0034] (2c) Surface XRD An XRD profile was measured in the range of 2θ = 10 to 140° when the surface of a diamond film was irradiated with X-rays using an XRD device (Rigaku Corporation, RINT-TTR III). This XRD measurement was performed under the following conditions: X-ray source: Cu-Kα rays, voltage: 50kV, current: 300mA, step angle: 0.020°, scan speed: 2.00° / min. As a result, the diamond (400) plane was detected as the main phase, and the (111) plane and (110) plane were detected as secondary phases. To evaluate the degree of diamond orientation, the ratio of the maximum peak intensity of the (400) plane to the maximum peak intensity of the (111) plane was calculated. Specifically, the maximum peak intensity near the (400) plane peak was calculated. ２ The maximum peak intensity I near the (111) plane peak. １ Ratio I ２ / I １ The peak intensity ratio I in this example was calculated. ２ / I １ The intensity ratio was 6.6, indicating that it is an oriented polycrystalline film oriented on the (400) plane (which is equivalent to the (100) plane). Note that when measuring diamond with XRD, the crystal plane with the strongest diffraction intensity is the (111) plane, while the (400) plane has relatively weak intensity (see ICDD card #01-071-3649 shown in Figure 2). Nevertheless, the intensity ratio I ２ / I １ The fact that the value is 6.6 suggests that the diamond film in this example is a strongly (100) plane-oriented film.

[0035] (2d) Cross-sectional EBSD An electron backscatter diffraction (EBSD) spectrometer (Nordlys Nano, Oxford Instruments) was attached to a SEM (SU-5000, Hitachi High-Technologies Corporation) to perform inverse pole figure orientation mapping of a diamond film in a field of view of 797 μm × 1061 μm. The conditions for this EBSD measurement were as follows: <EBSD Measurement Conditions> - Acceleration voltage: 15 kV - Spot intensity: 70 - Working distance: 22.5 mm - Step size: 0.5 μm - Sample tilt angle: 70° - Measurement program: Aztec (version 3.3)

[0036] Next, the diamond film 10 was polished on a plane perpendicular to the film surface using a CP polishing machine (manufactured by JEOL Ltd., IB-09010CP). Then, the cross-section of the diamond film 10 was observed using EBSD to obtain the inverse pole figure mapping shown in Figure 6A and the band contrast diagram shown in Figure 6B. From the obtained inverse pole figure mapping and band contrast diagram, it was found that (i) the shape of the diamond single crystal particles is columnar, (ii) the diamond film 10 is composed of multiple diamond single crystal particles having a single crystal structure in the approximately normal direction, (iii) the orientation of these diamond single crystal particles improves as they extend in the height direction, and (iv) each diamond single crystal particle is biaxially oriented, being (100) axially oriented in the approximately normal direction to the film surface and also oriented in the in-plane direction of the film.

[0037] Figures 6C and 6D show a mapping image of the tilt angle distribution from the (100) axis in the cross-section of the diamond film 10 in the same field of view as above, and the frequency distribution (histogram) of the tilt angle of the diamond single crystal grains from the (100) axis in the said mapping image, respectively. Region R from the interface between the Si substrate 12 and the diamond film 10 up to a height of 30 μm ０－３０ (See Figure 6C) The average tilt angle of the particles from the (100) axis was 8.5°, and the tilt angle distribution approximated a Gaussian distribution. Furthermore, the proportion (frequency) of particles with a tilt angle of 0.5–15° was 83%. In contrast, in region R with a height of 30–70 μm from the interface... ３０－７０ (See Figure 6C) The average tilt angle of the particles from the (100) axis was 2.4°, and the distribution approximated a Gaussian distribution. The proportion (frequency) of particles with a tilt angle of 0.5 to 15° was 99%.

[0038] Each diamond single crystal particle constituting the diamond film 10 is oriented in the in-plane direction (horizontal direction) parallel to the film surface of the diamond film 10, and the average twist angle of the diamond single crystal particles with respect to the (110) axis is in the region R from the interface between the Si substrate 12 and the diamond film 10 up to a height of 30 μm. ０－３０ At 8.2°, the twist angle approximated a Gaussian distribution. Also, in region R... ０－３０In this region, the proportion (frequency) of diamond single crystal grains with a twist angle of 0.5 to 15° was 92%. In contrast, in the region R with a height of 30 to 70 μm from the interface... ３０－７０ The average twist angle was 1.7°, and the twist angle distribution approximated a Gaussian distribution. Also, in region R ３０－７０ The proportion (frequency) of diamond single crystal grains with a twist angle of 0.5 to 15° was 99%.

[0039] Furthermore, in the band contrast diagram (Figure 6B), a straight line S parallel to the Si substrate 12 is shown in Figure 3, at a position 3 μm below the outermost surface of the diamond film 10 and at a position 3 μm above the interface between the Si substrate 12 and the diamond film 10. Ｔ , S Ｂ I drew a line. Straight line S Ｔ , S Ｂ For each of these, the straight line S Ｔ , S Ｂ Let n be the number of intersection points X between the diamond film 10 and the grain boundaries, and let L be the distance between each intersection point X that contains at least 10 intersection points X. Ｔ , L Ｂ This was defined as follows. And, as shown in Figure 3, D Ｔ = L Ｔ The value calculated by the formula / (n-1) is the average cross-sectional diameter D of the diamond single crystal grains 10a on the surface of the diamond film 10. Ｔ While D decided to do so, Ｂ = L Ｂ The value calculated by the formula / (n-1) is used to determine the average cross-sectional diameter of the diamond single crystal grains 10a at the interface between the Si substrate 12 and the diamond film 10 (i.e., the back surface 10c of the diamond film 10) as D Ｂ This was determined. As a result, the average cross-sectional diameter D in this example is Ｔ It is 7.9 μm, D Ｂ It is 1.0 μm, D Ｔ / D Ｂ The ratio was 1.0 or greater. The thickness T of the diamond film 10 was 79 μm, and the average cross-sectional diameter D was as described above. Ｔ The aspect ratio T / D is defined as the ratio of the thickness T of the diamond film 10 to the ratio of the diamond film 10 to the diamond film 10. Ｔ The answer was 10.

[0040] Examples 2 to 5 A diamond film was produced and various analyzes were performed in the same manner as in Example 1, except that the diamond film was formed at 1000°C by the microwave plasma CVD method described in (1) above for 19 hours (Example 2), 31 hours (Example 3), 40 hours (Example 4) or 50 hours (Example 5). The results were as shown in Tables 1 to 3. The results obtained in Example 1 are also shown together in Tables 1 to 3.

[0041]

[0042]

[0043]

[0044] 10: diamond film, 10a: single-crystal diamond particle, 10b: surface, 10c: back surface, 12: substrate, L Ｔ , L Ｂ : length, S Ｔ , S Ｂ : straight line, X: intersection point, T: thickness, R ０－３０ : region extending to a height of 30 µm from the interface, R ３０－７０ : region where the height from the interface is 30 to 70 µm

Claims

1. A diamond film composed of oriented polycrystalline diamond, wherein the oriented polycrystalline diamond includes a plurality of diamond single crystal particles having a single crystal structure in a direction substantially normal to the surface of the diamond film.

2. The diamond film according to claim 1, wherein the diamond film is (100) oriented.

3. The peak intensity of the (111) plane, measured by X-ray diffraction (XRD) on the surface of the diamond film. １ Peak intensity I of the (400) plane relative to ２ Ratio I ２ / I １ The diamond film according to claim 1 or 2, wherein the coefficient is 5.5 or higher.

4. The diamond film according to claim 1 or 2, wherein the (100) crystal orientation of each diamond single crystal particle, measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD), is distributed tilted at various tilt angles from a reference (100) crystal orientation, and the average tilt angle is 0.5 to 10°.

5. The diamond film according to claim 4, wherein more than 80% of the diamond single crystal particles measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD) have a tilt angle in the range of 0.5 to 10°.

6. The diamond film according to claim 1 or 2, wherein the diamond single crystal particles have crystal orientations that are generally aligned in the in-plane direction of the diamond film.

7. The diamond film according to claim 1 or 2, wherein the (110) crystal orientation of each diamond single crystal particle, measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD), is distributed rotated at various twist angles from a reference (110) crystal orientation, and the average twist angle is 0.5 to 15°.

8. The diamond film according to claim 7, wherein more than 80% of the diamond single crystal particles measured on the surface of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD) have a twist angle in the range of 0.5 to 15°.

9. The diamond film according to claim 1 or 2, wherein, when measured on a cross-section of the diamond film by inverse pole figure mapping of electron backscatter diffraction (EBSD), the diamond single crystal particles constituting the oriented polycrystalline diamond include a plurality of anisotropic particles that have grown in a direction away from the back surface of the diamond film, and 50% or more of the area of ​​the plurality of anisotropic particles is interrupted in the region near the back surface up to a depth of 20 μm from the back surface of the diamond film.

10. The diamond film according to claim 1 or 2, wherein the surface of the diamond film has an arithmetic mean roughness Ra of 0.6 nm or less.

11. The diamond film according to claim 1 or 2, wherein the diamond single crystal particles exposed on the surface of the diamond film are in communication with the back surface of the diamond film without the presence of grain boundaries.

12. The diamond film according to claim 1 or 2, wherein the diamond film has a thickness of 30 μm or more.

13. The average cross-sectional diameter D at the outermost surface of the diamond single crystal grains exposed on the surface of the diamond film. Ｔ The aspect ratio T / D is defined as the ratio of the thickness T of the diamond film to the ratio of the diamond film thickness T to the aspect ratio T / D Ｔ The diamond film according to claim 1 or 2, wherein the coefficient is 1.0 or greater.

14. The cross-sectional average diameter D at the outermost surface of the diamond single crystal particles on the back surface of the diamond film Ｂ , the cross-sectional average diameter D at the outermost surface of the diamond single crystal particles exposed on the surface of the diamond film Ｔ ratio D Ｔ / D Ｂ is greater than 1.

0. The diamond film according to claim 1 or 2.

15. The diamond film is 19.625 cm ２ A diamond film according to claim 1 or 2, having the above area.

16. The diamond film according to claim 1 or 2, wherein the diamond single crystal particles are doped with an n-type dopant or a p-type dopant.

Images