Homoepitaxial growth of alpha-SiC thin films and semiconductor devices fabricated thereon

• US 4,912,064 A
• Filed: 10/26/1987
• Issued: 03/27/1990
• Est. Priority Date: 10/26/1987
• Status: Expired due to Term

• Current Assignee: North Carolina State University Raleigh North Carolina
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Kong, Hua-Shuang, Davis, Robert F., Glass, Jeffrey T.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): WILCZEWSKI, MARY A
• Application Number:
  US07/113,573
• Time in Patent Office: 883 Days
• Field of Search: 437/100, 437/105, 437/106, 437/103, 148/DIG. 148, 156/DIG. 64, 156/610, 156/612, 156/600, 427/248.1, 427/249
• US Class Current: 438/507
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/36 Carbides
• CPC Class Codes: Y10S 148/148 Silicon carbide
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor
• CPC Class Codes: Y10S 438/973 Substrate orientation

Abstract

Device quality monocrystalline Alpha-SiC thin films are epitaxially grown by chemical vapor deposition on Alpha-SiC [0001] substrates prepared off axis.

Claims

1. A method of producing a device quality silicon carbide film on a silicon carbide substrate of the same polytype comprising:

homoepitaxially depositing a film of an Alpha-SiC polytype on a prepared planar surface of an Alpha-SiC substrate, wherein the planar surface is inclined more than one degree off axis with respect to a basal plane thereof substantially towards one of the <

1120>

directions.

2. A method as claimed in claim 1 wherein the polytype of both the substrate and the film is 6H SiC.

3. A method as claimed in claim 1 wherein the film is homoepitaxially deposited under conditions encouraging uniform growth rate thereacross, resulting in a film of substantially uniform thickness.

4. A method as claimed in claim 1 wherein the off axis inclination is in the range from approximately 3°

to approximately 12°

.

5. A method as claimed in claim 1 wherein the off axis inclination in the range from approximately 3°

to approximately 6°

.

6. A method as claimed in claim 1 wherein the off axis inclination is approximately 3°

.

7. A method as claimed in claim 1 wherein the planar surface of the substrate is prepared for the deposition step in such a manner as to expose on an atomic level a stepped surface which provides nucleation opportunities in all three directions to thereby encourage nucleation and subsequent crystal growth of a desired Alpha-SiC polytype.

8. A method as claimed in claim 7 wherein the substrate surface is prepared by polishing, oxidizing and etching said surface.

9. A method as claimed in claim 1 including the step of fabricating an electronic device on the film.

10. A method of producing a monocrystalline 6H SiC thin film homoepitaxially deposited on an off axis 6H SiC substrate, wherein the film is characterized by a smooth surface morphology, substantially uniform thickness and a low, device quality defect level, said method comprising:

lapping a 6H SiC substrate crystal to expose a planar surface that is inclined more than one degree off axis with respect a basal plane thereof substantially towards one of the <

1120>

directions;

preparing the off axis planar surface of the substrate to be receptive to epitaxial growth thereon;

heating the substrate crystal in a growth chamber;

introducing a carrier gas, a vaporized silicon-containing material and a vaporized carbon-containing material into the growth chamber while providing sufficient energy to create surface diffusion of silicon and carbon species at the substrate planar surface and establish a homoepitaxial growth of monocrystalline 6H SiC; and

maintaining the carrier gas, silicon-containing material and carbon-containing material flows and the energy levels for a time sufficient to grow a film of desired thickness.

11. A method as claimed in claim 10 wherein the step of preparing the off axis planar surface to be receptive to epitaxial growth comprises the steps of polishing, oxidizing and etching said surface.

12. A method as claimed in claim 10 wherein the 6H SiC substrate crystal is a wafer cut from a sublimation-grown crystal.

13. A method as claimed in claim 10 wherein the growth chamber is maintained at a temperature on the order of about 1350°

C. to about 1800°

C.

14. A method as claimed in claim 10 wherein the growth chamber is maintained at a temperature on the order of about 1400°

C. to about 1700°

C.

15. A method as claimed in claim 10 wherein the carrier gas is H₂.

16. A method as claimed in claim 10 wherein the carrier gas is H₂, the vaporized silicon-containing material is a SiH₄ source gas and the vaporized carbon-containing material is a C₂ H₄ source gas.

17. A method as claimed in claim 10 wherein the homoepitaxial growth of the monocrystalline 6H SiC film is achieved at temperatures that would produce a Beta-SiC film under identical growth conditions if grown directly on a basal plane of the 6H SiC substrate.

18. A method as claimed in claim 10 including the step of introducing a dopant into the growth chamber during epitaxial growth of the monocrystalline 6H SiC.

19. A method as claimed in claim 18 wherein the monocrystalline 6H SiC film is doped by bubbling an H₂ carrier gas through liquid Al(CH₃)₃.

20. A method of producing a device quality silicon carbide film on a silicon carbide substrate, said method comprising:

producing by sublimation a large, device quality Alpha-SiC single crystal;

slicing the crystal to form wafers;

preparing one of the wafers to establish a planar surface that is inclined more than one degree off axis with respect to a basal plane of the crystal substantially towards one of the <

1120>

directions;

depositing a film of Alpha-SiC on the planar surface of the substrate.

21. A method as claimed in claim 20 wherein the polytype of both the substrate and the film is 6H SiC and the angle of inclination is between approximately 3°

and approximately 12°

.