Silicon Carbide Devices Having Smooth Channels

• US 20090261351A1
• Filed: 04/16/2009
• Published: 10/22/2009
• Est. Priority Date: 05/24/2005
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Laughner, Michael, Das, Mrinal K.
• Granted Patent: US 8,188,483 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 29/0873 Drain regions
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/0886 Shape
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor

Abstract

Power devices are provided including a p-type conductivity well region and a buried p⁺ conductivity region in the p-type conductivity well region. An n⁺ conductivity region is provided on the buried p⁺ conductivity region. A channel region of the power device is provided adjacent the buried p⁺ conductivity region and n⁺ conductivity region, the channel region of the power device having a root mean square (RMS) surface roughness of less than about 1.0 Å.

Claims

1. A power device, comprising:

a p-type conductivity well region;

a buried p⁺ conductivity region in the p-type conductivity well region;

an n⁺ conductivity region on the buried p⁺ conductivity region; and

a channel region of the power device adjacent the buried p⁺ conductivity region and n⁺ conductivity region, the channel region of the power device having a root mean square (RMS) surface roughness of less than about 1.0 Å

.

2. The device of claim 1:

wherein the p-type conductivity well region comprises a p-type silicon carbide well region;

wherein the buried p⁺ conductivity region comprises a buried region of p⁺ silicon carbide in the p-type silicon carbide well region; and

wherein the n⁺ conductivity region comprises an n⁺ region of silicon carbide on the buried region of p⁺ silicon carbide.

3. The device of claim 2, further comprising a sacrificial oxide layer on a surface of the channel region having a thickness of from about 100 to about 1000 Å

, wherein the RMS surface roughness of the channel region is reduced to about 0.70 Å

after formation of the sacrificial oxide layer.

4. The device of claim 2, further comprising an n⁻

silicon carbide region on the channel region of the power device, the presence of the n⁻

silicon carbide region providing a reduction in a surface roughness of the channel region.

5. The device of claim 4, wherein the reduction in the surface roughness is a reduction in a root mean square (RMS) surface roughness of from at least about 28 Å

to less than about 1.0 Å

.

6. The device of claim 4, wherein n⁻

region of silicon carbide on the channel region has a thickness of from about 1000 to about 5000 Å

.

7. The device of claim 6, wherein the thickness of the n⁻

region of silicon carbide on the channel region is about 1500 Å

.

8. The device of claim 4, wherein the n⁻

region comprises a remaining portion of an n⁻

epitaxial layer on the channel region after removal of a removed portion of the n⁻

epitaxial layer.

9. The method of claim 8, wherein the n⁻

epitaxial layer has a thickness of from about 1500 Å

to about 6000 Å

before removal of the removed portion thereof.

10. The device of claim 4, further comprising an n-type region of silicon carbide in the p-type silicon carbide well region adjacent the channel region, wherein the channel region is defined between the buried region of p⁺ silicon carbide and the n-type region of silicon carbide and wherein the n⁻

region only remains on the channel region.

11. The device of claim 2, further comprising;

a silicon carbide substrate, wherein the p-type silicon carbide well region is provided on the silicon carbide substrate; and

an n⁻

silicon carbide layer between the silicon carbide substrate and the p-type silicon carbide well region,

wherein the p-type silicon carbide well region comprises an implanted region of p-type silicon carbide in the n⁻

silicon carbide layer;

wherein the buried region of p⁺ silicon carbide comprises an implanted region of p⁺ silicon carbide in the p-type silicon carbide well region; and

wherein the n⁺ region of silicon carbide comprises an implanted n-type region in the p-type silicon carbide well region on the buried region of p⁺ silicon carbide.

12. The device of claim 2, further comprising:

a silicon carbide substrate, wherein the p-type silicon carbide well region is provided on the silicon carbide substrate; and

an n⁻

silicon carbide layer between the silicon carbide substrate and the p-type silicon carbide well region,

wherein the p-type silicon carbide well region comprises a p-type epitaxial layer on the n⁻

silicon carbide layer;

wherein the buried region of p⁺ silicon carbide comprises an implanted region of p-type silicon carbide in the p-type silicon carbide well region; and

wherein the n⁺ region of silicon carbide comprises an implanted region of n-type silicon carbide in the p-type silicon carbide well region on the p⁺ region of silicon carbide.

13. The device of claim 2, further comprising an n-type region of silicon carbide in the p-type silicon carbide well region adjacent the channel region, wherein the channel region is defined between the buried region of p⁺ silicon carbide and the n-type region of silicon carbide and wherein the n-type region of silicon carbide is a Junction Field Effect Transistor (JFET) region of the power device.

14. The device of claim 2, further comprising:

a silicon carbide substrate, wherein the p-type silicon carbide well region is provided on the silicon carbide substrate; and

an n⁻

silicon carbide layer between the silicon carbide substrate and the p-type silicon carbide well region,

wherein the substrate comprises an n⁻

substrate which serves as a drift region of the power device, the device further comprising an n⁺ drain region on the substrate opposite the n⁻

silicon carbide layer.

15. The device of claim 14, wherein the n⁺ drain region comprises an implanted n⁺ drain region in the n⁻

substrate or an epitaxial n⁺ drain region on the n⁻

substrate.

16. The device of claim 2, wherein the power device comprises a Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

17. A Metal Oxide Semiconductor Field Effect Transistor (MOSFET) comprising a channel region having a root mean square (RMS) surface roughness of less than about 1.0 Å

.

18. The MOSFET of claim 17, further comprising a sacrificial oxide layer on a surface of the channel region having a thickness of from about 100 to about 1000 Å

, wherein the RMS surface roughness of the channel region is reduced to about 0.70 Å

after formation of the sacrificial oxide layer.

19. The MOSFET of claim 17, further comprising an n⁻

silicon carbide region on the channel region of the MOSFET, the presence of the n⁻

silicon carbide region providing a reduction in a surface roughness of the channel region.

20. The MOSFET of claim 19, wherein the reduction in the surface roughness is a reduction in a root mean square (RMS) surface roughness of from at least about 28 Å

to less than about 1.0 Å

.

21. The MOSFET of claim 19, wherein n⁻

region of silicon carbide on the channel region has a thickness of from about 1000 to about 5000 Å

.

22. The MOSFET of claim 21, wherein the thickness of the n⁻

region of silicon carbide on the channel region is about 1500 Å

.

23. The MOSFET of claim 19, wherein the n⁻

region comprises a remaining portion of an n⁻

epitaxial layer on the channel region after removal of a removed portion of the n⁻

epitaxial layer.

24. The MOSFET of claim 23, wherein the n⁻

epitaxial layer has a thickness of from about 1500 Å

to about 6000 Å

before removal of the removed portion thereof.

25. The MOSFET of claim 19, further comprising:

a silicon carbide substrate;

an n⁻

silicon carbide layer on the silicon carbide substrate;

a p-type silicon carbide well region on the n⁻

silicon carbide layer;

a buried region of p⁺ silicon carbide in the p-type silicon carbide well region; and

an n⁺ region of silicon carbide on the buried region of p⁺ silicon carbide, wherein the channel region of the MOSFET is adjacent the buried region of p⁺ and n⁺ region of silicon carbide.

26. The MOSFET of claim 25, further comprising an n-type region of silicon carbide in the p-type silicon carbide well region adjacent the channel region, wherein the channel region is defined between the buried region of p⁺ silicon carbide and the n-type region of silicon carbide and wherein the n⁻

region only remains on the channel region.

27. The MOSFET of claim 25, further comprising an n-type region of silicon carbide in the p-type silicon carbide well region adjacent the channel region, wherein the channel region is defined between the buried region of p⁺ silicon carbide and the n-type region of silicon carbide and wherein the n-type region of silicon carbide is a Junction Field Effect Transistor (JFET) region of the MOSFET.

28. The MOSFET of claim 25, wherein the substrate comprises an n⁻

substrate which serves as a drift region of the MOSFET, the MOSFET further comprising an n⁺ drain region on the substrate opposite the n⁻

silicon carbide layer.

29. The MOSFET of claim 28, wherein the n⁺ drain region comprises an implanted n⁺ drain region in the n⁻

substrate or an epitaxial n⁺ drain region on the n⁻

substrate.

30. A power device, comprising:

a p-type conductivity well region;

a buried p⁺ conductivity region in the p-type conductivity well region;

an n⁺ conductivity region on the buried p⁺ conductivity region; and

a channel region of the power device adjacent the buried p⁺ conductivity region and n⁺ conductivity region; and

an n⁻

conductivity region on the channel region of the power device, the presence of the n⁻

conductivity region providing a reduction in a surface roughness of the channel region.

31. The device of claim 30:

wherein the p-type conductivity well region comprises a p-type silicon carbide well region;

wherein the buried p⁺ conductivity region comprises a buried region of p⁺ silicon carbide in the p-type silicon carbide well region;

wherein the n⁺ conductivity region comprises an n⁺ region of silicon carbide on the buried region of p⁺ silicon carbide; and

wherein the n⁻

conductivity region comprises an n⁻

silicon carbide region.