AlN single crystal substrate

Abstract

Provided is an AlN single crystal substrate which does not crack even when having a large size with a diameter of 100 mm or more. The AlN single crystal substrate is composed of an AlN single crystal and has a diameter of 100 mm or more.

Description

Technical Field

[0001] This invention relates to AlN single crystal substrates. Background Technology

[0002] In recent years, AlN single-crystal substrates have been developed as substrates for deep ultraviolet LEDs. Sublimation methods have been explored as methods for manufacturing AlN single crystals. For example, Patent Document 1 (Japanese Patent Application Publication No. 2019-19042) discloses a method for manufacturing AlN single crystals, in which AlN single crystals are grown on a SiC seed substrate in at least two stages using the sublimation method.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-19042 Summary of the Invention

[0006] As mentioned above, when AlN single crystals are manufactured using the sublimation method, cracking sometimes occurs due to the difference in thermal expansion coefficients between the SiC seed substrate and the AlN single crystal. This problem becomes more pronounced with larger substrate sizes. Therefore, manufacturing large AlN single crystal substrates with diameters exceeding 100 mm without causing cracking has historically been difficult.

[0007] The inventors of this invention recently discovered that by using an AlN bond composed of AlN seed crystals and AlN sintered body to grow AlN single crystals, it is possible to provide large-sized AlN single crystal substrates with a diameter of 100 mm or more that do not crack.

[0008] Therefore, the object of the present invention is to provide an AlN single crystal substrate that, although large in size with a diameter of 100 mm or more, has not cracked.

[0009] According to the present invention, the following solution is provided.

[0010] [Option 1]

[0011] An AlN single-crystal substrate, wherein,

[0012] The AlN single crystal substrate is made of AlN single crystal and has a diameter of more than 100 mm.

[0013] [Option 2]

[0014] According to the AlN single crystal substrate described in Scheme 1, wherein...

[0015] The AlN single crystal substrate has a diameter of 150 mm or more.

[0016] [Option 3]

[0017] According to the AlN single-crystal substrate described in scheme 1 or 2, wherein,

[0018] The half-width of the X-ray rocking curve of the (002) plane of the AlN single crystal in at least one surface of the AlN single crystal substrate is 20 to 350 arcsec.

[0019] [Option 4]

[0020] According to any one of Schemes 1 to 3, the AlN single crystal substrate wherein...

[0021] The half-width of the X-ray rocking curve of the (102) plane of the AlN single crystal in at least one surface of the AlN single crystal substrate is 20 to 500 arcsec.

[0022] [Option 5]

[0023] According to any one of Schemes 1 to 4, the AlN single crystal substrate, wherein,

[0024] The defect density on at least one surface of the AlN single crystal substrate is 1.0 × 10⁻⁶. 3 ~1.0×10 7 cm -2 .

[0025] [Option 6]

[0026] A device comprising an AlN single-crystal substrate as described in any one of embodiments 1 to 5. Attached Figure Description

[0027] Figure 1 This is a schematic process diagram illustrating the manufacturing method of an AlN single crystal substrate. Detailed Implementation

[0028] AlN single crystal substrate

[0029] like Figure 1 As shown in (iii), the AlN single-crystal substrate 20 of the present invention is composed of AlN single crystal 18 and has a diameter of 100 mm or more. That is, according to the present invention, it is possible to provide an AlN single-crystal substrate 20 that is large in size with a diameter of 100 mm or more but does not crack. As described above, when AlN single crystals are manufactured using the sublimation method, the larger the substrate size, the more significant the cracking caused by the difference in the coefficients of thermal expansion between the SiC seed substrate and the AlN single crystal. Therefore, it has not been easy in the past to manufacture a large AlN single-crystal substrate with a diameter of 100 mm or more without cracking. In this respect, the large-size AlN single-crystal substrate 20 of the present invention overcomes such conventional problems.

[0030] The AlN single-crystal substrate 20 has a diameter of 100 mm or more, preferably 150 mm or more or 200 mm or more. There is no particular upper limit to the diameter of the AlN single-crystal substrate 20; typically, the diameter is 300 mm or less, and more typically, 250 mm or less. Typically, the AlN single-crystal substrate 20 has a circular shape. In this specification, "circular shape" does not need to be a complete circle; it can be a generally circular shape that can be roughly identified as a circle overall. For example, it can be a shape obtained by cutting off a portion of a circle for determining crystal orientation or other purposes (e.g., a circular shape including an orientation flat or a cut).

[0031] The thickness of the AlN single crystal substrate 20 is not particularly limited, but is preferably 200-700 μm, more preferably 250-680 μm, and even more preferably 300-650 μm.

[0032] The AlN single-crystal substrate 20 exhibits good crystallinity. Regarding good crystallinity, the profiles of the X-ray rocking curves (hereinafter referred to as XRC) of the (002) and (102) planes of the AlN single crystal can be measured, and their half-widths are evaluated. Specifically, the XRC half-width of the (002) plane of the AlN single crystal in at least one surface of the AlN single-crystal substrate 20 is preferably 20 to 350 arcsec, more preferably 100 to 300 arcsec, and even more preferably 100 to 280 arcsec. If the XRC half-width of the (002) plane is within such a range, it has the advantage that dislocations are not generated within the formed film during device fabrication, resulting in good performance. Furthermore, the XRC half-width of the (102) plane of the AlN single crystal in at least one surface of the AlN single crystal substrate 20 is preferably 20 to 500 arcsec, more preferably 200 to 450 arcsec, and even more preferably 200 to 400 arcsec. If the XRC half-width of the (102) plane is within such a range, it has the following advantages: no dislocations are generated in the formed film during device fabrication, resulting in good performance. The surface having the XRC half-width of the (102) plane within the aforementioned range is preferably the same as the surface having the XRC half-width of the (002) plane within the aforementioned range. Furthermore, it is preferable that both sides of the AlN single crystal substrate 20 have the XRC half-width of the (102) plane and / or the XRC half-width of the (002) plane within the aforementioned range. The XRC profiles of the (002) and (102) planes of the AlN single crystal can be measured using a conventional XRD apparatus (e.g., a Bruker-AXS D8 DISCOVER) and accompanying XRD analysis software (e.g., Bruker-AXS "LEPTOS" Ver4.03), based on the order described in the embodiments described later.

[0033] The AlN single-crystal substrate 20 can have a low defect density. Specifically, the defect density on at least one surface of the AlN single-crystal substrate 20 is preferably 1.0 × 10⁻⁶. 3 ~1.0×10 7 cm -2 More preferably 1.0×10 6 ~8.0×10 6 cm -2 Further preferred is 1.0×10 6 ~6.0×10 6 cm -2If the defect density is within such a range, it has the following advantages: no dislocations are generated in the formed film during device fabrication, resulting in good performance. The surface having a defect density within the aforementioned range is preferably the same surface of the AlN single-crystal substrate 20 as the surface having the XRC half-width of the (102) surface within the aforementioned numerical range and the surface having the XRC half-width of the (002) surface within the aforementioned numerical range. Furthermore, it is preferable that both surfaces of the AlN single-crystal substrate 20 have a defect density within the aforementioned numerical range. The defect density can be measured based on the order described in the embodiments described later.

[0034] Devices

[0035] The AlN single-crystal substrate 20 of the present invention has excellent properties and is suitable for large sizes, thus enabling its application in various devices. Therefore, according to a preferred embodiment of the present invention, a device incorporating the AlN single-crystal substrate 20 is provided. Preferred examples of such devices include: deep ultraviolet LEDs, ultraviolet lasers, power devices, MEMS devices, HMETs (high electron mobility transistors), etc.

[0036] Manufacturing method

[0037] The preferred method for manufacturing the AlN single-crystal substrate of the present invention will be described below. For example... Figure 1 As shown, the method includes the following steps: preparing an AlN bond 16 composed of an AlN seed crystal 12 and an AlN sintered body 14; and performing heat treatment on the AlN bond 16 to grow an AlN single crystal 18 from the AlN seed crystal 12. According to this method, although it is a suitable technique for large-diameter applications, it is possible to manufacture an AlN single crystal substrate 20 with high productivity without causing cracking.

[0038] That is, as described above, when AlN single crystals are manufactured using the sublimation method, cracking sometimes occurs due to the difference in the coefficients of thermal expansion between the SiC seed substrate and the AlN single crystal. This problem becomes more pronounced with larger substrate sizes. To address this issue, for example, sublimation is performed only during the fabrication of the AlN seed crystal 12. Afterward, the AlN seed crystal 12 is transferred to the AlN sintered body, and AlN single crystals are grown from the AlN seed crystal in the region of the AlN sintered body. Thus, the precipitation of the AlN seed crystal 12 based on the sublimation method is carried out to a thickness sufficient to prevent cracking even at large sizes (e.g., diameters of 100 mm or more). Then, the growth of AlN single crystal 18 from the AlN seed crystal 12 is performed through the transformation from the AlN sintered body 14 (AlN polycrystalline) to AlN single crystal 18, rather than through the sublimation method. In this case, since the coefficients of thermal expansion of the AlN seed crystal 12 and the AlN single crystal 18 are very close, the possibility of cracking due to the difference in coefficients of thermal expansion, as is the case when a SiC seed substrate is used, is extremely low. Therefore, according to the present invention, large-sized (e.g., diameter 100 mm or more) AlN single crystal substrates 20 can be obtained with good quality without going through processes that are prone to cracking.

[0039] The following describes each step of the manufacturing process for AlN single-crystal substrates.

[0040] (1) Preparation of AlN conjugate

[0041] like Figure 1 As shown in (ii), an AlN bond 16 composed of AlN seed crystals 12 and AlN sintered body 14 is prepared. The AlN sintered body 14 is a polycrystalline AlN, and therefore is a ceramic material composed of multiple AlN crystal particles bonded together. The diameter of the AlN bond 16 is preferably 100 mm or more, more preferably 150 mm or more or 200 mm or more. The diameter of the AlN bond 16 is typically 300 mm or less, more typically 250 mm or less. The thickness of the AlN seed crystals 12 is not particularly limited, but is preferably 0.1 to 700 μm, more preferably 0.5 to 450 μm, and even more preferably 1 to 5 μm. The thickness of the AlN sintered body 14 is not particularly limited, but is preferably 200 to 700 μm, more preferably 250 to 650 μm, and even more preferably 350 to 550 μm.

[0042] The AlN bond 16 can be formed by AlN seed crystal 12 and AlN sintered body 14, and can be prepared by any method. Preferably, the following processes (a) to (c) are used. Figure 1 The AlN bond 16 is prepared using the methods shown in (i) and (ii). The order of steps (a) and (b) can be reversed.

[0043] (a) Preparation of AlN sintered body

[0044] Prepare an AlN sintered body 14. For example, mix AlN powder and a sintering aid, shape the resulting mixed powder, and fire the resulting shaped body to produce the AlN sintered body 14. Specifically, the preparation process (process (a)) of the AlN sintered body 14 is preferably performed as described below, including (a1) the preparation of the mixed powder, (a2) the preparation of the shaped body, and (a3) ​​the sintering of the shaped body. It should be noted that the AlN sintered body 14 is not limited to the method including processes (a1) to (a3) ​​below, and can be prepared using various known methods.

[0045] (a1) Preparation of mixed powder

[0046] First, AlN powder is mixed with a powder containing at least one rare earth element to prepare a mixed powder with an AlN content of 95% by weight or more. AlN powder is the main component of the mixed powder, while the powder containing the rare earth element is used as a sintering aid. Preferred examples of rare earth elements include Y, La, Ce, Sm, Eu, Gd, Dy, and Yb. These rare earth elements are preferably contained in the powder in the form of oxides, carbonates, hydroxides, or complex oxides. Furthermore, the sintering aid is not limited to powder containing rare earth elements; it can also be powder containing alkaline earth elements such as Mg and Ca. The AlN content in the mixed powder is 95% by weight or more, typically 96% by weight or more, more typically 97% by weight or more, and even more typically 98% by weight or more. The content of the sintering aid in the mixed powder is not particularly limited, but is preferably 0.1 to 5.0% by weight, more preferably 0.2 to 4.0% by weight, even more preferably 0.4 to 3.0% by weight, and particularly preferably 0.5 to 2.0% by weight.

[0047] (a2) Fabrication of the molded body

[0048] The obtained mixed powder is shaped into a specified form to create a molded body. There are no particular restrictions on the molding method; it can be done by compression molding (e.g., uniaxial compression molding) or sheet molding (e.g., scraper molding).

[0049] (a3) Sintering of the molded body

[0050] The obtained molded body is fired to produce an AlN sintered body 14 with an average crystal grain size of 1 to 40 μm. This firing is preferably performed by hot pressing, which includes holding the molded body at a specified firing temperature and pressure for a specified time. The firing temperature in the hot pressing is preferably 1500 to 2000 °C, more preferably 1600 to 1900 °C, and even more preferably 1650 to 1800 °C. The holding time (i.e., firing time) at the above firing temperature is preferably 1 to 10 hours, more preferably 2 to 8 hours, and even more preferably 4 to 6 hours. Furthermore, the pressing load during hot pressing is preferably 0 to 30 MPa, more preferably 0 to 20 MPa, and even more preferably 0 to 10 MPa. The average crystal grain size of the AlN sintered body 14 (the average grain size of the plurality of AlN crystal particles constituting the AlN sintered body 14) is 1 to 40 μm, preferably 2 to 25 μm, and more preferably 3 to 10 μm. The average crystal grain size can be determined using the method described in the examples described later.

[0051] (b) Preparation of AlN template

[0052] like Figure 1 As shown in (i), an AlN template 13 is prepared. The AlN template 13 is a composite material having an AlN seed crystal 12 and a substrate 10 supporting the AlN seed crystal 12. The substrate 10 is preferably a substrate on which the AlN seed crystal 12 can be formed. Preferred examples of such a substrate 10 include: SiC substrate, sapphire substrate, Si substrate, etc. The formation of the AlN seed crystal 12 on the substrate 10 is preferably performed using a vapor phase method. Examples of vapor phase methods include: sublimation, chemical vapor deposition (CVD), sputtering, hydride vapor deposition (HVPE), etc., with sublimation being preferred.

[0053] (c) Bonding of AlN sintered bodies toward AlN seed crystals and removal of the substrate

[0054] like Figure 1As shown in (i) and (ii), an AlN sintered body 14 is bonded to an AlN seed crystal 12 toward the obtained AlN template 13, and the substrate 10 is removed to obtain an AlN bonded body 16. This bonding can be performed using a surface activation method or a plasma bonding method. In the case of a surface activation method, bonding can be performed ideally in the following order. First, the surface of the AlN sintered body 14 is mirror-polished. Next, the surfaces of the AlN seed crystal 12 and the AlN sintered body 14 are activated. Surface activation can be performed using irradiation with a neutral beam such as an Ar beam. Then, the AlN template 13 and the AlN sintered body 14 are overlapped so that the activated surfaces of the AlN seed crystal 12 and the AlN sintered body 14 are in contact with each other to form a laminate. The laminate is then bonded by applying a load of 100 to 20000 N under vacuum. After bonding, the unwanted substrate 10 is removed to expose the AlN seed crystal 12, thereby obtaining an AlN bond 16 composed of the AlN seed crystal 12 and the AlN sintered body 14. The substrate 10 can be removed using known methods such as grinding or reactive ion etching (RIE).

[0055] In performing the above-described neutral beam-based surface activation, an inert gas is introduced into the chamber, and a high voltage is applied from a DC power supply to the electrodes disposed within the chamber. With this configuration, the electric field generated between the electrodes (positive electrode) and the chamber (negative electrode) causes electrons to move, generating a beam of atoms and ions based on the inert gas. Upon reaching the grid, the ion beam is neutralized at the grid, thus the beam of neutral atoms is emitted from the high-speed atomic beam source. The atoms constituting the beam are preferably inert gas elements (e.g., Ar, Ne, Kr, He, N, or Xe). The voltage used for activation by beam irradiation is, for example, 0.5–2.0 kV, and the current is, for example, 50–200 mA.

[0056] It should be noted that in the example shown, the AlN sintered body 14 is bonded to only one side of the AlN seed crystal 12. However, the AlN sintered body 14 can also be bonded to both sides of the AlN seed crystal 12.

[0057] (2) Growth of AlN single crystals

[0058] like Figure 1As shown in (ii) and (iii), the AlN bond 16 is heat-treated to grow an AlN single crystal 18 from the AlN seed crystal 12. That is, by heat-treating the AlN bond 16, the AlN sintered body 14 gradually transforms into an AlN single crystal 18 starting from the portion in contact with the AlN seed crystal 12, resulting in the growth of the AlN single crystal 18. The growth of the AlN single crystal 18 based on this method differs from the sublimation method, which is prone to cracking due to the use of a SiC seed substrate with a different coefficient of thermal expansion than the AlN single crystal. Since the coefficients of thermal expansion of the AlN seed crystal 12 and the AlN single crystal 18 are very close, even with large sizes (e.g., diameters of 100 mm or more), there is no need to worry about cracking, and the AlN single crystal 18 can be grown to the desired thickness. This heat treatment is preferably performed in an inert gas atmosphere such as nitrogen. The preferred firing temperature in the heat treatment is 2000–2300°C, more preferably 2100–2250°C, and even more preferably 2150–2200°C. The holding time (i.e., firing time) at the above firing temperature is preferably 1 to 50 hours, more preferably 3 to 45 hours, and even more preferably 5 to 40 hours. This heat treatment can be performed using atmospheric pressure firing or hot pressing firing. The pressing load during heat treatment is preferably 0 to 30 MPa, more preferably 0 to 20 MPa, and even more preferably 0 to 10 MPa. Two AlN bond bodies 16 can be overlapped and heat-treated.

[0059] At this time, as Figure 1 As shown in (ii) and (iii), it is preferable to grow the AlN single crystal 18 integrally within the AlN sintered body 14 to more effectively prevent cracking. However, as long as cracking is not a problem, the AlN single crystal 18 can be grown to the middle of the AlN sintered body 14, leaving a portion of the AlN sintered body 14 remaining (in this case, it is desirable to remove the remaining portion of the AlN sintered body 14 by grinding or the like). By grinding and polishing the surface of the AlN single crystal 18 thus obtained, a self-standing AlN single crystal substrate 20 can be obtained.

[0060] Example

[0061] The invention will be further illustrated by the following examples. However, the invention is not limited to these examples.

[0062] Examples 1 to 11

[0063] (1) Preparation of AlN sintered body

[0064] Aluminum nitride powder (manufactured by Tokuyama Co., Ltd., grade F), yttrium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd.), dysprosium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd.), and samarium oxide powder (manufactured by Yttrium Co., Ltd.) were prepared. Aluminum nitride powder and yttrium oxide powder (Examples 1-6 and 9-11), dysprosium oxide powder (Example 7), or samarium oxide powder (Example 8) were mixed according to the weight ratios given in Table 1 to obtain a blended powder. This blended powder was uniaxially pressed and then heated and pressurized to the maximum temperature and pressure given in Table 1, and held at these maximum temperatures and pressures for the time given in Table 1, thereby performing hot pressing sintering. Both sides of the obtained hot-pressed sintered body were mirror-polished to obtain a plate-shaped AlN sintered body (AlN polycrystalline).

[0065] The average grain size of the obtained AlN sintered body was measured in the following order, and the results are shown in Table 1.

[0066] (Determination of average crystal grain size)

[0067] Regarding the grain size of the sintered body, the cross-section of the sintered body was mirror-polished, and the microstructure in the range of 64μm × 48μm was confirmed using a SEM (JSM-IT500LA manufactured by Nippon Electron Ltd.) at a magnification of 2000x. The intercept method was used to solve the problem. Specifically, in the SEM image obtained by observing the polished surface of the sintered body, any number of line segments with a length of 40μm or more were drawn on the scale of the SEM image, and the number of crystalline particles n traversed by these line segments was determined. It should be noted that if the end of the line segment is located within a crystalline particle, the crystalline particle is counted as 1 / 2. The value obtained by dividing the length L of the line segment by n is taken as the average crystal grain size (i.e., the average intercept length) I, and the value obtained by multiplying I by a coefficient of 1.5 is taken as the average sintered grain size.

[0068] (2) Creation of AlN template based on sublimation method

[0069] Inside a crucible serving as a crystal growth container, a SiC substrate is placed, and AlN raw material powder is placed in a manner that avoids contact with the SiC substrate. The growth container is pressurized at 50 kPa under a N2 atmosphere, and the portion near the AlN raw material powder in the growth container is heated to 2100°C using high-frequency induction heating. On the other hand, the portion near the SiC substrate in the growth container is heated to a temperature 200°C lower (i.e., 1900°C). The above heating temperature is maintained for 30 minutes, thereby forming an AlN seed film on the SiC substrate. The surface of the AlN seed is mirrored, resulting in a SiC substrate with AlN seed attached, serving as an AlN template.

[0070] (3) Bonding of AlN sintered bodies toward AlN seed crystals and removal of substrate

[0071] The surfaces of the AlN sintered body and the AlN seed side of the AlN template were irradiated with a high-speed neutral Ar atom beam (accelerating voltage: 1 kV, Ar flow rate: 60 sccm) for 70 seconds to activate these surfaces. The AlN sintered body and the AlN template were then overlapped in contact with the AlN seed crystal, and a load of 1000 N was applied under vacuum to bond the AlN sintered body and the AlN template. The resulting bond was then ground using a #2000 abrasive stone to remove the SiC substrate. The surface was further smoothed using diamond abrasive, resulting in an AlN bond composed of the AlN sintered body and the AlN seed crystal. The AlN bond was disc-shaped, with a diameter of 100 mm in Examples 1-8 and 150 mm in Examples 9 and 10. The thickness of the AlN seed crystal was 2 μm in Examples 1-10 and 4 μm in Example 11. In addition, in Examples 1 to 11, the thickness of the AlN sintered body is 400 μm.

[0072] (4) Growth of AlN single crystals

[0073] The obtained AlN composite was hot-pressed at 2160°C and 13MPa for 40 hours under N2 atmosphere, thereby growing AlN single crystals from AlN seeds throughout the AlN sintered body.

[0074] (5) Subsequent processes (grinding and polishing)

[0075] In Examples 1-5 and 7-10, the surface of the obtained AlN single crystal was subjected to a specified amount of grinding and polishing, thereby obtaining a self-standing AlN single crystal substrate with a thickness of 0.3 mm. In Example 6, the surface of the AlN single crystal was ground and polished in the same manner as above to obtain a self-standing AlN single crystal substrate with a thickness of 0.3 mm; however, cracking occurred. In Example 11, the AlN single crystal cracked during growth, therefore, no grinding or polishing was performed.

[0076] (6) Evaluation of AlN single crystals

[0077] The following evaluation is made regarding the obtained AlN single crystals.

[0078] (6a) Evaluation of AlN single crystal substrate fabrication

[0079] The state of AlN single crystals during the growth process (4) and subsequent processes (5) was observed and evaluated based on the following criteria. The results are shown in Table 1.

[0080] • Evaluation A: The AlN single crystal grew without cracking. Furthermore, the AlN single crystal did not crack during subsequent processes (grinding and polishing).

[0081] • Evaluation B: The AlN single crystal grew without cracking. Cracks occurred in the AlN single crystal during subsequent processes (grinding and polishing), however, it was determined that by changing the conditions of the subsequent processes to more stable conditions, cracking could be prevented.

[0082] • Evaluation C: The AlN single crystal cracked during the growth process, making it impossible to obtain a self-standing AlN single crystal substrate.

[0083] (6b) Half-width of X-ray rocking curve

[0084] XRC measurements were performed on the (002) plane of the AlN single crystal substrate surface (the surface opposite to the AlN seed crystal) using a multifunctional high-resolution X-ray diffractometer (Bruker-AXS D8 DISCOVER). The conditions for this XRC measurement are as follows.

[0085] <XRD Measurement Conditions>

[0086] • Tube voltage: 40kV

[0087] Tube current: 40mA

[0088] • Detector: Tripple Ge (220) Analyzer

[0089] • Parallel monochromatic CuKα rays with a half-width of 28 seconds were achieved using a Ge(022) asymmetric reflection monochromator.

[0090] • Step width: 0.001°

[0091] • Scanning speed: 0.5 seconds / step

[0092] In practice, after adjusting 2θ, ω, χ, and φ to establish the axis in a manner that produces the peak of the (002) plane of the AlN single crystal, and using a 3mm anti-scattering slit, the range of ω = 14.5–19.5° was measured. The half-width of the XRC profile of the (002) plane of the AlN single crystal was determined as follows: after smoothing the profile using XRD analysis software (LEPTOS Ver4.03 manufactured by Bruker-AXS), peak search was performed. As a result, the half-width of the XRC profile of the (002) plane of the AlN single crystal substrate is shown in Table 1.

[0093] In addition, XRC measurements were performed on the (102) plane of the AlN single crystal substrate surface (the surface opposite to the AlN seed crystal). A Bruker-AXS D8-DISCOVER was used as the XRD apparatus. After adjusting 2θ, ω, χ, and φ to establish the axis so that the peak of the (102) plane of the AlN single crystal appeared, ω was set to 24.5–29.5° for measurement. Other conditions and analytical methods were performed under the same conditions as for the (002) plane XRC measurement. The half-width of the XRC profile of the (102) plane of the AlN single crystal substrate surface is shown in Table 1.

[0094] (6c) Defect density

[0095] The defect density of the obtained AlN single-crystal substrate (the surface opposite to the AlN seed crystal) was evaluated as follows: the entire surface area was measured using X-ray topology (XRTmicron manufactured by Rigaku Corporation). Here, the defect density was 1.0 × 10⁻⁶. 5 cm -2 Under the above circumstances, it is difficult to calculate the accurate number of etch pits using X-ray morphology. Therefore, an etch pit evaluation using KOH melt etching was performed to measure the defect density on the surface of the AlN single crystal substrate. Specifically, the surface of the AlN single crystal substrate was immersed in a molten solution of KOH:NaOH mixed in a weight ratio of 1:1 and heated to 450°C for 5 minutes. After etching, the defect density was measured using an optical microscope.

[0096] Example 12 (Compare)

[0097] The AlN single crystals were prepared using the sublimation method as described below, and the evaluation was performed in the same manner as in Examples 1-11. The results are shown in Table 1.

[0098] (Fabrication of AlN single crystal substrate)

[0099] A 100 mm diameter SiC substrate, serving as the growth vessel, was placed inside a crucible. AlN raw material powder was placed in the crucible without contacting the SiC substrate. The growth vessel was pressurized at 50 kPa under a nitrogen atmosphere. High-frequency induction heating was used to heat the area near the AlN raw material powder in the growth vessel to 2100°C, while the area near the SiC substrate was heated to a lower temperature (1900°C), 200°C lower. This heating temperature was maintained for 10 hours, thereby allowing AlN single crystals to precipitate and grow on the SiC substrate. A SiC substrate with AlN single crystals was obtained. After cooling, the AlN single crystals were examined, and cracking was observed. It is believed that the large difference in thermal expansion between the SiC substrate and the AlN single crystals caused the cracking due to thermal stress resulting from the difference in thermal expansion during cooling.

[0100] Table 1

[0101]

Claims

1. An AlN single-crystal substrate, which is composed of AlN single crystals and has a diameter of 100 mm or more, The AlN single crystal substrate is characterized in that... The half-width of the X-ray rocking curve of the (002) plane of the AlN single crystal in at least one surface of the AlN single crystal substrate is 20 to 350 arcsec.

2. An AlN single-crystal substrate, which is composed of AlN single crystals and has a diameter of 100 mm or more. The AlN single crystal substrate is characterized in that... The half-width of the X-ray rocking curve of the (102) plane of the AlN single crystal in at least one surface of the AlN single crystal substrate is 20 to 500 arcsec.

3. An AlN single-crystal substrate, which is composed of AlN single crystals and has a diameter of 100 mm or more. The AlN single crystal substrate is characterized in that... The defect density on at least one surface of the AlN single crystal substrate is 1.0 × 10⁻⁶. 3 ~1.0×10 7 cm -2 .

4. An AlN single-crystal substrate, characterized in that, The AlN single crystal substrate is made of AlN single crystal and has a diameter of more than 150 mm.

5. A device, characterized in that, The device comprises an AlN single crystal substrate as described in any one of claims 1 to 4.

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