Method of improving mechanically prepared substrate surfaces of alpha silicon carbide for deposition of beta silicon carbide thereon and resulting product

• US 5,200,022 A
• Filed: 10/03/1990
• Issued: 04/06/1993
• Est. Priority Date: 10/03/1990
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: Cree Research, Inc. (Wolfspeed, Inc.)
• Inventors: Carter, Calvin H. Jr., Kong, Hua-Shuang
• Primary Examiner(s): WILCZEWSKI, MARY A
• Application Number:
  US07/592,548
• Time in Patent Office: 916 Days
• Field of Search: 156/610, 156/612, 156/613, 156/DIG. 64, 156/DIG. 68, 437/81, 437/126, 437/133, 437/946, 437/970, 437/93, 437/100, 148/DIG. 148
• US Class Current: 117/95
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/36 Carbides
• CPC Class Codes: Y10S 148/148 Silicon carbide

Abstract

The invention is a method of improving a mechanically prepared surface of alpha silicon carbide for increasing the polytype purity of an epitaxial layer of beta silicon carbide grown thereon. The method comprises decreasing the frequency of exposed higher energy lattice positions along a mechanically prepared {0001} surface of a 6H alpha silicon carbide substrate by adding atoms to vacant lattice positions and by increasing the average height and separation between steps on a mechanically prepared {0001} surface of 6H silicon carbide.

Claims

1. A method of improving a surface of alpha silicon carbide for the growth thereon of a beta silicon carbide epitaxial layer, the method comprising:

mechanically preparing the surface of a {0001} plane of an alpha silicon carbide substrate; and

thereafter

introducing atoms selected from the group consisting of aluminum, gallium and phosphorous into vacant lattice positions along the mechanically prepared surface to thereby prevent the vacant lattice positions from encouraging the repetitive growth of 6H silicon carbide at those lattice positions so that chemical vapor deposition conditions that are otherwise favorable for epitaxial growth of beta silicon carbide upon the basal plane will result in such growth of beta silicon carbide upon the mechanically prepared alpha silicon carbide substrate.

2. A method of growing epitaxial layers of beta silicon carbide on non-natural surfaces of alpha silicon carbide, the method comprising:

separating a bulk single crystal of 6H silicon carbide into a substrate crystal with at least one of the {0001} surfaces thereof exposed;

introducing atoms other than silicon or carbon lattice positions along the {0001} surface of the 6H silicon carbide substrate to thereby prevent the vacant lattice positions from encouraging the repetitive growth of 6H silicon carbide at those lattice positions; and

exposing the {0001}6H surface to carbon containing and silicon containing species under conditions for which the growth of beta silicon carbide is thermodynamically favored for a time sufficient for a desired epitaxial layer of beta silicon carbide to form upon the {0001} surface of the silicon carbide substrate.

3. A method according to claim 2 wherein the step of exposing the {0001} surface to carbon containing and silicon containing species comprises exposing the (0001) face of the substrate so that a beta silicon carbide thin film is deposited in the growth direction on the (0001) surface such that the (111) crystallography of the beta silicon carbide thin film matches the (0001) surface of the substrate and such that the beta silicon carbide (101) face is parallel to the alpha silicon carbide (1120) face and the beta silicon carbide (111) face is parallel to the alpha silicon carbide (0001) face.

4. A method according to claim 2 wherein the step of separating a bulk crystal comprises slicing a bulk crystal into individual wafers and polishing the exposed surface.