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DE-112014004088-B4 - Process for the formation of silicon carbide

DE112014004088B4DE 112014004088 B4DE112014004088 B4DE 112014004088B4DE-112014004088-B4

Abstract

Process for the formation of silicon carbide, comprising the steps i) Providing a sublimation oven (200) comprising an oven jacket (201), at least one heating element (202) arranged outside the oven jacket (201), and a hot zone (203) arranged inside the oven jacket (201) surrounded by insulation (204), wherein the hot zone (203) comprises: a) a crucible (210) having an upper region (220) and a lower region (240); b) a crucible cover (215) that tightly seals the crucible (210); c) a seeding module arranged in the upper region (220) of the crucible (210), the seeding module comprising a silicon carbide seeding crystal (100) having an upper surface (150) and a lower surface (160) exposed to the upper region of the crucible (210), ii) Manufacturing, outside the crucible (210), a source module (235) containing an outer annular chamber (231) and a hollow inner chamber, iii) Arranging a solid silicon carbide precursor in the outer annular chamber of the source module (235) while the source module (235) is located outside the crucible (210), iv) After arranging the silicon carbide precursor in the outer annular chamber (231) of the source module (235), while the source module (231) is located outside the crucible (210), arrange the source module (231) containing the silicon carbide precursor inside the crucible (210), such that the silicon carbide precursor is in the lower region (240) of the crucible (210) is positioned, which faces the lower surface (160) of the silicon carbide seed crystal. v) Heating the hot zone (203) with the heating element (202) to sublime the silicon carbide precursor, and vi) Formation of silicon carbide on the lower surface (160) of the silicon carbide seed crystal (100).

Inventors

  • Roman V. Drachev
  • Parthasarathy Santhanaraghavan
  • Andriy M. Andrukhiv
  • David S. Lyttle

Assignees

  • GTAT CORPORATION

Dates

Publication Date
20260513
Application Date
20140905
Priority Date
20130906

Claims (20)

  1. A process for the formation of silicon carbide, comprising the steps: i) providing a sublimation furnace (200) comprising a furnace jacket (201), at least one heating element (202) arranged outside the furnace jacket (201), and a hot zone (203) arranged inside the furnace jacket (201) surrounded by insulation (204), wherein the hot zone (203) comprises: a) a crucible (210) having an upper region (220) and a lower region (240); b) a crucible cover (215) that tightly seals the crucible (210); c) a seeding module located in the upper region (220) of the crucible (210), the seeding module comprising a silicon carbide seed crystal (100) having an upper surface (150) and a lower surface (160) exposed to the upper region of the crucible (210), ii) fabricating, outside the crucible (210), a source module (235) comprising an outer annular chamber (231) and a hollow inner chamber, iii) arranging a solid silicon carbide precursor in the outer annular chamber of the source module (235) while the source module (235) is located outside the crucible (210), iv) after arranging the silicon carbide precursor in the outer annular chamber (231) of the source module (235) while the source module (231) is located outside the crucible (210), Arrange the source module (231), which contains the silicon carbide precursor, inside the crucible (210) such that the silicon carbide precursor is positioned in the lower region (240) of the crucible (210), which faces the lower surface (160) of the silicon carbide seed crystal. v) Heat the hot zone (203) with the heating element (202) to sublime the silicon carbide precursor, and vi) Form silicon carbide on the lower surface (160) of the silicon carbide seed crystal (100).
  2. Procedure according to Claim 1 , wherein the seed crystal module comprises a seed crystal holder (120) having at least one vapor release opening (130), and the silicon carbide seed crystal (100) is positioned in the seed crystal holder (120).
  3. Procedure according to Claim 2 , wherein the seed crystal holder (120) comprises a plurality of vapor release openings (130).
  4. Procedure according to Claim 3 , wherein the seed crystal holder (120) has a central axis (215) perpendicular to the lower surface (160) of the silicon carbide seed crystal (100) and wherein the plurality of vapor release openings (130) are arranged symmetrically around the central axis (215).
  5. Procedure according to Claim 3 , wherein the silicon carbide seed crystal (100) is a circular silicon carbide wafer and wherein the plurality of vapor release openings (130) are equidistant from the central axis (215).
  6. Procedure according to Claim 2 , wherein the crucible (210) comprises one or more ventilation holes (260), the hot zone (203) further comprises at least one vapor release ring (280) comprising one or more holes (270), and wherein the vapor release ring (280) is arranged above the seed crystal holder (120) with at least one of the holes (270) aligned with at least one of the ventilation holes (260) of the crucible (210).
  7. Procedure according to Claim 2 , wherein the vapor release opening (130) is located at a position below the lower surface (160) of the silicon carbide seed crystal (100).
  8. Procedure according to Claim 1 , wherein the upper surface (150) of the silicon carbide seed crystal (100) comprises a seed crystal protective layer.
  9. Procedure according to Claim 8 , where the seed crystal protective layer has a thickness of less than 250 micrometers.
  10. Procedure according to Claim 8 , where the seed crystal protective layer has a thickness of less than 100 micrometers.
  11. Procedure according to Claim 10 , where the thickness of the seed crystal protective layer is 10 micrometers to 90 micrometers.
  12. Procedure according to Claim 10 , where the thickness of the seed crystal protective layer is 30 micrometers to 80 micrometers.
  13. Procedure according to Claim 10 , where the thickness of the seed crystal protective layer is 50 micrometers to 70 micrometers.
  14. Procedure according to Claim 8 , wherein the seed crystal protective layer comprises at least two coating layers.
  15. Procedure according to Claim 14 , wherein at least one coating layer is a hardened photoresist layer.
  16. Procedure according to Claim 15 , where the hardened photoresist layer has a thickness of 2 micrometers to 5 micrometers.
  17. Procedure according to Claim 14 , wherein at least one coating layer is a graphite coating layer.
  18. Procedure according to Claim 17 , where the graphite coating layer has a thickness of 20 micrometers to 30 micrometers.
  19. Procedure according to Claim 8 , wherein the silicon carbide seed crystal (100) has a silicon side and a carbon side and wherein the upper surface is the silicon side.
  20. Procedure according to Claim 8 , wherein the silicon carbide seed crystal (100) has a silicon side and a carbon side and wherein the upper surface is the carbon side.

Description

Cross-reference to related registrations This application is linked to the preliminary US patent application serial number 617874,620 related to the patent application filed on September 6, 2013. The entire contents of that patent application are incorporated herein by reference. Background of the invention 1. Field of the invention The present invention relates to a process for producing bulk silicon carbide with low defect density. 2. Description of the state of the art Silicon carbide (SiC) has gained significant interest in recent years due to its outstanding chemical, physical, and electrical properties. In particular, it has been found that bulk single-crystal SiC is useful in semiconductor applications, including, for example, as a substrate for components in power electronics and LEDs. Other applications for this material are also emerging. Silicon carbide can be produced by a variety of methods known in the field. For example, large single crystals of silicon carbide are produced using a physical vapor transport (PVT) method. In this method, a source, such as powdered silicon carbide, is placed in a high-temperature region of a crystal growth furnace and heated. A seed crystal, such as a silicon carbide single-crystal wafer, is also placed in a lower-temperature region. The silicon carbide is heated, subliming, and the resulting vapors reach the cooler silicon carbide seed crystal, onto which material is deposited. Alternatively, the source can be a mixture of silicon and carbon particles that reacts upon heating to form SiC, which subsequently sublimes and recrystallizes on the seed crystal. Although large silicon carbide single crystals can be produced using a crystal growth furnace, the process is often difficult to regulate. For example, it is critical that the process conditions, such as the temperature gradient between the source and the seed crystal, are kept constant throughout the crystal growth process, which typically takes place over several days at temperatures above 2000°C, in order to produce a single crystal with consistently uniform properties. Small variations in the process conditions can lead to large changes in the quality of the grown silicon carbide single crystals. As growth progresses, sublimation of the seed crystal and/or the growing crystal can also occur if the process conditions are not properly regulated. Furthermore, the product quality can be affected by the types of components used in the crystal growth chamber, as some can decompose depending on the growth conditions and thus chemically interfere with the growth process. As a result, silicon carbide grown in a sublimation furnace often contains defects in the crystals, such as low-angle grain boundaries, dislocations, Si and C second-phase inclusions, various polytype inclusions, and microtubes, which impair the material's performance properties. Even if specific conditions for a single-crystal growth process can be maintained to produce a high-quality product, variability from run to run is typically observed, since, for example, any fluctuation in the source, seed crystal, or equipment components can produce inconsistencies in the product. Methods and equipment for the production of silicon carbide and related technologies are described, for example, in the publications US 5 944 890 A , US 6 451 112 B1 , US 2002 0 083 892 A1 , US 2003 0 094 132 A1 , US 2006 0 102 068 A1 , US 2007 0 283 880 A1 , US 2008 0 026 591 A1 , US 2011 0 214 606 A1 , US 2012 0 006 255 A1 , US 2012 0 103 249 A1 , US 2014 0 220 298 A1 , US 2014 0 158 042 A1 , US 2011 0 111 171 A , CN 1 02 414 349 A , JP 2001-114599 A , JP 2008-115033 A , JP 2009-256159 A , JP 2011-020860 A , JP 2013-136494 A , JP 2013-124196 A , JP 4 860 164 B2 , EP 2 954 101 B1 , EP 2 954 100 B1 , KR 10 2012 0 139 398 A , WO2001/063020 A1 , WO 97/07265 A1 and WO2014/123636 A1 For this reason, until now there has been no furnace or process for reliable and repeatable silicon carbide sublimation that can efficiently and cost-effectively produce high-quality large silicon carbide single crystals. Therefore, there is a need in industry for an improved silicon carbide growth apparatus and an improved silicon carbide growth process. Summary of the invention The present invention relates to a method for producing silicon carbide. The method comprises the steps of providing a sublimation furnace comprising a furnace jacket, at least one heating element arranged outside the furnace jacket, and a hot zone arranged inside the furnace jacket, which is surrounded by insulation. The hot zone comprises a crucible having an upper region and a lower region, a crucible cover that tightly seals the crucible, a silicon carbide precursor arranged in the lower region of the crucible, and a seed crystal module arranged in the lower region of the crucible, wherein the seed crystal module has a silicon carbide seed crystal having an upper surface and a lower surface exposed to the upper region of t