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US-12618172-B2 - Seed substrate for epitaxial growth use and method for manufacturing same, and semiconductor substrate and method for manufacturing same

US12618172B2US 12618172 B2US12618172 B2US 12618172B2US-12618172-B2

Abstract

A seed substrate for epitaxial growth has a support substrate, a planarizing layer of 0.5 to 3 μm provided on the top surface of the support substrate, and a seed crystal layer provided on the top surface of the planarizing layer. The support substrate includes a core of group III nitride polycrystalline ceramics and a 0.05 to 1.5 μm encapsulating layer that encapsulates the core. The seed crystal layer is provided by thin-film transfer of 0.1 to 1.5 μm of the surface layer of Si<111> single crystal with oxidation-induced stacking faults (OSF) of 10 defects/cm 2 or less. High-quality, inexpensive seed substrates with few crystal defects for epitaxial growth of epitaxial substrates and solid substrates of group III nitrides such as AlN, AlxGa1-xN (0<X<1) and GaN are obtained.

Inventors

  • Yoshihiro Kubota
  • Ippei KUBONO

Assignees

  • SHIN-ETSU CHEMICAL CO., LTD.
  • SHIN-ETSU HANDOTAI CO., LTD.

Dates

Publication Date
20260505
Application Date
20220304
Priority Date
20210310

Claims (20)

  1. 1 . A seed substrate for epitaxial growth comprising: a support substrate; a planarizing layer provided on an upper surface of the support substrate, the planarizing layer having a thickness of 0.5 to 3.0 μm; and a seed crystal layer provided on an upper surface planarizing layer, wherein the support substrate comprises: a core formed by group III nitride polycrystalline ceramics; and an encapsulating layer that encapsulates the core, the encapsulating layer having a thickness of 0.05 to 1.5 μm, and the seed crystal layer is provided by thin-film transfer of 0.1 to 1.5 μm of a surface layer of Si<111> single crystal with oxidation-induced stacking faults of no more than 10 defects/cm 2 .
  2. 2 . A seed substrate for epitaxial growth comprising: a support substrate; a planarizing layer provided on an upper surface of the support substrate, the planarizing layer having a thickness of 0.5 to 3.0 μm; and a seed crystal layer provided on an upper surface planarizing layer, wherein the support substrate comprises: a core formed by group III nitride polycrystalline ceramics; and an encapsulating layer that encapsulates the core, the encapsulating layer having a thickness of 0.05 to 1.5 μm, and the seed crystal layer has oxidation-induced stacking faults of no more than 10 defects/cm 2 , and the thickness of the seed crystal layer is 0.1 to 1.5 μm.
  3. 3 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the group III nitride polycrystalline ceramics forming the core are AlN ceramics.
  4. 4 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the encapsulating layer includes at least a layer of Si 3 N 4 .
  5. 5 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the planarizing layer comprises SiO 2 and/or silicon oxynitride (Si x O y N z ) or AlAs.
  6. 6 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the electrical resistivity (at room temperature) of Si<111> forming the seed crystal layer is 1 kΩ-cm or higher.
  7. 7 . The seed substrate for epitaxial growth as claimed in claim 1 , further comprises a stress-adjusting layer on the bottom surface of the support substrate.
  8. 8 . The seed substrate for epitaxial growth as claimed in claim 7 , wherein the stress-adjusting layer has a thermal expansion coefficient that enables further correction of the warpage after the planarizing layer is provided, and consists of polycrystalline Si prepared by a method selected from at least the sputtering, plasma CVD, and LPCVD.
  9. 9 . The seed substrate for epitaxial growth as claimed in claim 7 , wherein the stress-adjusting layer is provided as polycrystalline Si with SiO 2 and/or silicon oxynitride (Si x O y N z ) interposing just below the bottom surface of the support substrate.
  10. 10 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the encapsulation layer is deposited by LPCVD.
  11. 11 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the planarizing layer is formed by depositing SiO 2 and/or silicon oxynitride (Si x O y N z ) or AlAs on one or all sides of the top surface of the support substrate by one of plasma CVD, LPCVD, and low-pressure MOCVD.
  12. 12 . The seed substrate for epitaxial growth as claimed in claim 1 , wherein the seed crystal layer is provided by ion implanting hydrogen and/or He into Si<111> single crystal with oxidation-induced stacking faults of 10 defects/cm 2 or less and electrical resistivity (at room temperature) of 1 kΩ-cm or higher, followed by transferring a thin film of the Si<111> single crystal of 0.1 to 1.5 μm by physical means at 450° C. or lower.
  13. 13 . A semiconductor substrate on which a III-V semiconductor thin film is deposited on the top surface of a seed substrate for epitaxial growth according to claim 1 .
  14. 14 . The semiconductor substrate as claimed in claim 13 , wherein the III-V semiconductor thin film is a nitride semiconductor thin film containing Ga and/or Al.
  15. 15 . A manufacturing method of seed substrate for epitaxial growth comprising: preparing a core consisting of group III nitride polycrystalline ceramics; obtaining a support substrate by depositing an encapsulating layer so as to wrap the core, the encapsulating layer having a thickness of 0.05 to 1.5 μm; depositing a planarizing layer on an upper surface of the support substrate, the planarizing layer having a thickness of 0.5 to 3.0 μm; and providing a seed crystal layer by thin-film transfer of 0.1 to 1.5 μm of the surface layer of Si<111> single crystal with oxidation-induced stacking faults of no more than 10 defects/cm 2 on the top surface of the planarizing layer.
  16. 16 . The manufacturing method of seed substrate for epitaxial growth as claimed in claim 15 , wherein the encapsulation layer is deposited by the LPCVD.
  17. 17 . The manufacturing method of seed substrate for epitaxial growth as claimed in claim 15 , wherein the planarizing layer is formed by depositing SiO 2 and/or silicon oxynitride (Si x O y N z ) or AlAs on one or all sides of the top surface of the support substrate by one of plasma CVD, LPCVD, and low-pressure MOCVD.
  18. 18 . The manufacturing method of seed substrate for epitaxial growth as claimed in claim 15 , wherein in the step of providing the seed crystal layer, the seed crystal layer is provided by ion implanting hydrogen and/or He into Si<111> single crystal with oxidation-induced stacking faults of 10 defects/cm 2 or less and electrical resistivity (at room temperature) of 1 kΩ-cm or more, followed by transferring a thin film of the Si<111> single crystal of 0.1 to 1.5 μm by physical means at 450° C. or less.
  19. 19 . The manufacturing method of seed substrate for epitaxial growth as claimed in claim 15 , further providing a stress-adjusting layer on the bottom surface of the support substrate.
  20. 20 . The manufacturing method of seed substrate for epitaxial growth as claimed in claim 19 , wherein the stress-adjusting layer has a thermal expansion coefficient that enables further correction of the warpage after the planarizing layer is provided, and consists of polycrystalline Si prepared by a method selected from at least the sputtering, plasma CVD, and LPCVD.

Description

TECHNICAL FIELD The present invention relates to seed substrates used for epitaxial growth of epitaxial substrates and solid substrates of group III nitrides with few defects and excellent characteristics, such as aluminum nitride (AlN), aluminum gallium nitride (AlxGa1-xN (0<x<1)), and gallium nitride (GaN), and manufacturing method thereof. More specifically, it relates to seed substrates for epitaxial growth of epitaxial substrates and solid substrates of group III nitrides such as AlN, AlxGa1-xN (0<X<1) and GaN-based materials with extremely low crystal defects, warpage and voids, and high quality and low cost, and manufacturing method thereof. BACKGROUND ART Group III nitride crystal substrates such as AlN- and GaN-based substrates have a wide band gap and excellent high-frequency characteristics with short wavelength luminescence and high breakdown voltage. Therefore, group III nitride substrates are expected to be applied to devices such as light-emitting diodes (LEDs), lasers, Schottky diodes, power devices, and high-frequency devices. For example, with regard to AlN-based crystal substrates, the recent outbreak of coronavirus and other viruses has triggered a growing demand for AlN and/or AlxGa1-Xn (0.5<X<1) single crystals for light emitting diodes, especially in the deep ultraviolet region (UVC; 200-280 nm), for the purpose of bacterial and virus elimination. However, at present, these single-crystal substrates of AlN and/or AlxGa1-Xn (0.5<X<1) have many defects, are of low quality and high cost, and do not have the expected characteristics when various devices are made. Hence, the wide spread of these substrates and the expansion of their applications are limited. On the other hand, GaN-based crystal substrates are required to have higher high-frequency characteristics and greater breakdown voltage performance with the start of 5G communications and the shift to Evs in automobiles. As a result, GaN-based crystal substrates with very few crystal defects and low-cost epitaxial substrates and solid substrates are also in demand. However, as with AlN-based substrates, GaN-based substrates also have many crystal defects and are of low quality, but their prices are high. Therefore, the widespread use of GaN-based substrates for the aforementioned devices has been prevented, and further improvement is desired. For example, as described in Non-Patent Document 1 and Non-Patent Document 2, AlN single-crystal substrates are difficult to manufacture by the melt method commonly used for silicon (Si) single-crystals, etc. because AlN has no melting point. So they are usually manufactured by the sublimation method (modified Raleigh method) using silicon carbide (SiC) or AlN as seed crystals at 1700 to 2250° C. under an N2 atmosphere. Alternatively, they are made by the hydride vapor phase epitaxy (HVPE) on sapphire substrates or AlN substrates obtained by the sublimation method, as disclosed in Patent Document 1 and Non-Patent Document 3. Since AlN single crystals manufactured by the sublimation method require high temperatures for crystal growth, only small-diameter substrates of 2 to 4 inches in diameter can be obtained at present due to equipment limitations, and they are extremely expensive. The dislocation density of the resulting AlN single crystals is relatively low at <105 cm−2, but on the other hand, the crystals are colored by carbon and metallic impurities derived from charcoal materials such as crucibles and insulation materials, and have the disadvantages of low resistivity and low UV transmission. On the other hand, AlN single crystals made by hydride vapor phase epitaxy (HVPE) on sapphire substrates are relatively inexpensive and have little coloration, but the difference in lattice constants between AlN and sapphire results in high dislocation density and low resistivity of the AlN crystal. AlN crystals obtained by HVPE deposition on sublimation method AlN substrates have relatively low dislocation density, but are opaque to deep UV emission and have low resistivity due to colorant contamination from the underlying substrate AlN. In addition, the conventional use of expensive sublimation method AlN substrates as a base substrate that also serves as seed crystals has the disadvantage of being extremely costly. As for GaN substrates, bulk GaN substrates made by growing GaN crystals in liquid ammonia or Na flux have relatively few defects and are of high quality, but they are extremely expensive because they require high-temperature, high-pressure equipment. In addition, it is incredibly costly because it is used as a base substrate that also serves as a seed crystal, as is the case with the AlN substrate of the sublimation method described above. On the other hand, if heteroepitaxial growth is performed on sapphire and other substrates using the MOCVD or hydride vapor deposition (HVPE or THVPE), which grow crystals in the vapor phase, it is possible in principle to achieve higher crystal quality