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DE-112014004096-B4 - Process for the production of bulk silicon carbide

DE112014004096B4DE 112014004096 B4DE112014004096 B4DE 112014004096B4DE-112014004096-B4

Abstract

A method 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, a lower region and one or more ventilation holes (270); b) a crucible cover that tightly seals the crucible (210); c) a solid silicon carbide precursor (230) contained in a source module (235) arranged in the lower region of the crucible (210), wherein the source module (235) is removable from the crucible (210), and d) an independent seed crystal module removable from the crucible (210), which, when arranged in the upper region of the crucible (210), forms a space between the crucible cover and an entire upper surface of an upper section of a seed crystal holder (120) of the seed crystal (100), the seed crystal module comprising a plurality of vapor release openings (130, 140) and a silicon carbide seed crystal (100) arranged in the seed crystal holder (120), the plurality of vapor release openings (130, 140) in the seed crystal holder (120) being formed as a plurality of holes arranged around a central axis (215) perpendicular to the lower surface (160) of the silicon carbide seed crystal (100), e) a vapor release ring (280) having one or more holes (270), wherein at least one of the one or more holes (270) of the vapor release ring (280) is aligned with at least one of the one or more ventilation holes (260) of the crucible (210), wherein the vapor release ring (280) is in or above the seed crystal holder (120) or is provided between the outside of the seed crystal holder (120) and the crucible wall; ii) Heating the hot zone (203) with the at least one heating element (202) in order to sublimate the solid silicon carbide precursor (230) contained in the source module (235), iii) Formation of silicon carbide on the lower surface (160) of the silicon carbide seed crystal (100); iv) Removal of the seed crystal module including the silicon carbide formed on the lower surface (160) of the silicon carbide seed crystal (100); and v) Removal of the source module (235) including the sublimated solid silicon carbide precursor (230).

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 (18)

  1. A method for the formation of silicon carbide, comprising the steps of 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, a lower region, and one or more ventilation holes (270); b) a crucible cover that tightly seals the crucible (210); c) a solid silicon carbide precursor (230) contained in a source module (235) arranged in the lower region of the crucible (210), wherein the source module (235) is removable from the crucible (210), and d) an independent seed crystal module removable from the crucible (210), which, when arranged in the upper region of the crucible (210), forms a space between the crucible cover and an entire upper surface of an upper section of a seed crystal holder (120) of the seed crystal (100), wherein the seed crystal module comprises a plurality of vapor release openings (130, 140) and a silicon carbide seed crystal (100) arranged in the seed crystal holder (120), wherein the plurality of vapor release openings (130, 140) in the seed crystal holder (120) are located under a lower The surface (160) of the silicon carbide seed crystal (100) is formed as a plurality of holes arranged around a central axis (215) perpendicular to the lower surface (160) of the silicon carbide seed crystal (100); e) a vapor release ring (280) having one or more holes (270), wherein at least one of the one or more holes (270) of the vapor release ring (280) is aligned with at least one of the one or more vent holes (260) of the crucible (210), and wherein the vapor release ring (280) is provided in or above the seed crystal holder (120) or between the outer surface of the seed crystal holder (120) and the crucible wall; ii) Heating the hot zone (203) with the at least one heating element (202) to sublime the solid silicon carbide precursor (230) contained in the source module (235); iii) Forming the silicon carbide on the lower surface (160) of the silicon carbide seed crystal (100); iv) Removing the seed crystal module, including the silicon carbide formed on the lower surface (160) of the silicon carbide seed crystal (100); and v) Removing the source module (235), including the sublimed solid silicon carbide precursor (230).
  2. Procedure according to Claim 1 , wherein the source module (235) comprises a precursor chamber (231) and wherein the solid silicon carbide precursor (230) is contained in the precursor chamber (231).
  3. Procedure according to Claim 1 , wherein the solid silicon carbide precursor (230) is porous.
  4. Procedure according to Claim 3 , wherein the solid silicon carbide precursor (230) has a density that is less than the density of silicon carbide.
  5. Procedure according to Claim 1 , wherein the upper surface (150) of the silicon carbide seed crystal (100) comprises a seed crystal protective layer (110).
  6. Procedure according to Claim 5 , wherein the seed crystal protective layer (110) has a thickness of less than 250 micrometers.
  7. Procedure according to Claim 5 , wherein the seed crystal protective layer (110) has a thickness of less than 100 micrometers.
  8. Procedure according to Claim 5 , wherein the seed crystal protective layer (110) comprises at least two coating layers.
  9. Procedure according to Claim 5 , wherein the seed crystal protective layer (110) comprises at least one hardened coating layer.
  10. Procedure according to Claim 1 , wherein the silicon carbide seed crystal (100) has a silicon side and a carbon side and wherein the upper surface (150) of the silicon carbide seed crystal (100) is the silicon side.
  11. Procedure according to Claim 1 , wherein the silicon carbide seed crystal (100) has a silicon side and a carbon side and wherein the upper surface (150) of the silicon carbide seed crystal (100) is the carbon side.
  12. Procedure according to Claim 1 , wherein the hot zone (203) is arranged along the central axis (215).
  13. Procedure according to Claim 1 , wherein the insulation (204) comprises a plurality of layers of fibrous thermal insulating material made of graphite felt.
  14. Procedure according to Claim 1 , wherein the crucible (210) has a cylindrical shape.
  15. Procedure according to Claim 1 , wherein the upper region of the crucible (210) has a cylindrical shape having an upper diameter, and the lower region of the crucible (210) has a cylindrical shape having a lower diameter, and wherein the upper diameter is larger than the lower diameter.
  16. Procedure according to Claim 1 , wherein the heating element (202) is an induction heating device.
  17. Procedure according to Claim 1 , wherein the silicon carbide that is formed is a silicon carbide single crystal body having a circular cross-sectional shape in a direction parallel to the silicon carbide seed crystal (100).
  18. Procedure according to Claim 1 , where the silicon carbide has a total defect number of less than 8000/cm 2 .

Description

Background of the invention 1. Field of the invention The present invention relates to a sublimation furnace and to methods 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 of… US 5 944 890 A , US 6 451 112 B1 , US 2002 0 023 581 A1 , 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 0 103 249 A1 , US 2012 0 032 150 A1 , US 2014 0 220 298 A1 , CN 1 570 225 A , CN 1 02 414 349 A , JP 4 880 164 B2 , JP S61-024472 A , JP H06-316499 A , JP 2003-523918 A , JP 2009-274933 A , JP 2011-168431 A , WO 2001/063020 A1 and WO 2014/123636 A1 describe. 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 object of the invention is to provide a process for the formation of silicon carbide that can efficiently and cost-effectively produce high-quality large silicon carbide single crystals. This problem is solved by the features of claim 1. A method for producing silicon carbide has the features of claim 1. 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 substantially solid silicon carbide precursor arranged in the lower region of the crucible, and a seed crystal module arranged in the upper region of the crucible, wherein the seed crystal module comprises a silicon carbide seed crystal having an upper surface and a lower surface exposed to the upper region of the crucible, the lower surface facing the substantially solid silicon carbide p