Methods of fabricating silicon carbide crystals

• US 7,501,022 B2
• Filed: 10/04/2006
• Issued: 03/10/2009
• Est. Priority Date: 05/21/2001
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Mueller, Stephan
• Primary Examiner(s): Kunemund; Robert M
• Assistant Examiner(s): Song; Matthew J
• Application Number:
  US11/542,987
• Publication Number:
  US 20070022945A1
• Time in Patent Office: 888 Days
• Field of Search: 117/84, 117/88, 117/94, 117/97, 117/911, 117/951
• US Class Current: 117/84
• CPC Class Codes: C30B 23/00 Single-crystal growth by condensing evaporated or sublimed materials
• CPC Class Codes: C30B 23/025 characterised by the substrate
• CPC Class Codes: C30B 29/36 Carbides
• CPC Class Codes: Y10S 117/911 Seed or rod holders

Abstract

Methods for producing silicon carbide crystals, seed crystal holders and seed crystal for use in producing silicon carbide crystals and silicon carbide crystals are provided. Silicon carbide crystals are produced by forcing nucleation sites of a silicon carbide seed crystal to a predefined pattern and growing silicon carbide utilizing physical vapor transport (PVT) so as to provide selective preferential growth of silicon carbide corresponding to the predefined pattern. Seed holders and seed crystals are provided for such methods. Silicon carbide crystals having regions of higher and lower defect density are also provided.

Claims

1. A method of producing a silicon carbide boule having a substantially single polytype, the method comprising:

forcing preferential nucleation sites on a surface of a silicon carbide seed crystal having the substantially single polytype to a predefined pattern; and

growing the silicon carbide boule utilizing physical vapor transport (PVT) so as to provide selective preferential growth of silicon carbide on the silicon carbide seed crystal corresponding to the predefined pattern;

wherein forcing preferential nucleation sites comprises forming a pattern on the surface of the seed crystal so as to provide first regions of the seed crystal which extend beyond second regions of the seed crystal; and

wherein forming a pattern comprises forming a pattern of vertical sidewalls in the exposed surface of the seed crystal wherein the vertical sidewalls are perpendicular to the surface of the silicon carbide seed crystal; and

wherein growing the silicon carbide boule comprises preferentially growing silicon carbide from the vertical sidewalls.

2. The method of claim 1, wherein the pattern comprises stripes in the seed crystal.

3. The method of claim 2, wherein a center to center spacing of adjacent stripes is about 0.5 mm to about 3 mm.

4. The method of claim 1, wherein the pattern comprises a plurality of posts.

5. The method of claim 4, wherein the posts are substantially circular.

6. The method of claim 1, wherein the first regions extend beyond the second regions by a distance of about 0.25 mm to about 0.3 mm.

7. The method of claim 1, wherein the second regions have widths of about 0.5 mm to about 5 mm.

8. The method of claim 1, wherein the first regions have widths of about 0.5 mm to about 5 mm.