Silicon carbide power devices with self-aligned source and well regions

• US 7,381,992 B2
• Filed: 07/11/2006
• Issued: 06/03/2008
• Est. Priority Date: 04/24/2003
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ryu, Sei-Hyung
• Primary Examiner(s): Huynh; Andy
• Application Number:
  US11/456,642
• Publication Number:
  US 20060237728A1
• Time in Patent Office: 693 Days
• Field of Search: 257/77, 257E29297-E29298, 257/E21.603, 257/E21.605, 438/105, 438/931
• US Class Current: 257/77
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• 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: H01L 29/7828 without inversion channel, e.g. vertical ACCUFETs, normally-on vertical MISFETs
• CPC Class Codes: H01L 29/7838 without inversion channel, e.g. buried channel lateral MISFETs, normally-on lateral MISFETs, depletion-mode lateral MISFETs
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor

Abstract

Silicon carbide semiconductor devices and methods of fabricating silicon carbide semiconductor devices are provided by successively etching a mask layer to provide windows for formation of a source region of a first conductivity type, a buried silicon carbide region of a second conductivity type opposite to the first conductivity type and a second conductivity type well region in a first conductivity type silicon carbide layer. The source region and the buried silicon carbide region are formed utilizing a first window of the mask layer. Then, the well region is formed utilizing a second window of the mask layer, the second window being provided by a subsequent etch of the mask layer having the first window.

Claims

1. A silicon carbide power semiconductor device, comprising:

a first silicon carbide layer having a first conductivity type;

a source region in the first silicon carbide layer and having the first conductivity type, the source region having a higher carrier concentration than a carrier concentration of the first silicon carbide layer and extending to a first surface of the first silicon carbide layer;

a buried region of silicon carbide of the second conductivity type in the first silicon carbide layer adjacent a bottom portion of the source region and at a depth in the first silicon carbide layer greater than a depth of the source region;

a well region of silicon carbide of the second conductivity type in the first silicon carbide layer on a first side of the source region and extending toward the first surface of the first silicon carbide layer, the well region having a lower carrier concentration than a carrier concentration of the buried region;

a plug region of silicon carbide of the second conductivity type on a second side of the source region, opposite the first side of the source region, and extending to the first face of the first silicon carbide layer;

a gate oxide on the first silicon carbide layer, the well region and the source region;

a gate contact on the gate oxide;

a source contact on the plug region and the source region; and

a drain contact on the first silicon carbide layer opposite the first surface of the first silicon carbide layer.

2. The silicon carbide power semiconductor device of claim 1, wherein the source region has dopants of the first conductivity type and dopants of a second conductivity type opposite the first conductivity type.

3. The silicon carbide power semiconductor device of claim 1, wherein the first conductivity type is n-type and the second conductivity type is p-type.

4. The silicon carbide power semiconductor device of claim 1, further comprising threshold adjustment regions of first conductivity type silicon carbide in the first silicon carbide layer and extending on coplanar surfaces of the source region and the well region and being disposed between the well region and the first face of the first layer of silicon carbide.

5. The silicon carbide power semiconductor device of claim 4, wherein the threshold adjustment regions extend to a depth of from about 0.01 μ

m to about 0.5 μ

m into the first layer of silicon carbide and have a carrier concentration of from about 10¹⁵ to about 10¹⁹ cm<sup>−

3</sup>.

6. The silicon carbide power semiconductor device of claim 1, further comprising a first silicon carbide epitaxial layer on the first face of the first silicon carbide layer between the gate oxide and the first silicon carbide layer.

7. The silicon carbide power semiconductor device of claim 6, wherein the first silicon carbide epitaxial layer has a thickness of from about 6 μ

m to about 200 μ

m and a carrier concentration of from about 1×

10¹⁴ to about 5×

10¹⁶ cm<sup>−

3</sup>.

8. The silicon carbide power semiconductor device of claim 6, further comprising threshold adjustment regions of first conductivity type silicon carbide in the first silicon carbide layer and extending from the source region, the threshold adjustment regions being disposed between the well region and the first face of the first layer of silicon carbide.

9. The silicon carbide power semiconductor device of claim 8, wherein the threshold adjustment regions extend to a depth of from about 0.01 μ

m to about 0.5 μ

m into the first layer of silicon carbide and have a carrier concentration of from about 10¹⁵ to about 10¹⁹ cm<sup>−

3</sup> and wherein the first silicon carbide epitaxial layer has a thickness of from about 6 to about 200 μ

m and a carrier concentration of from about 1×

10¹⁴ to about 5×

10¹⁶ cm<sup>−

3</sup>.

10. The silicon carbide power semiconductor device of claim 1, further comprising a second layer of silicon carbide of the first conductivity type disposed between the first layer of silicon carbide and the drain contact, the second layer of silicon carbide having a higher carrier concentration than the first layer of silicon carbide.

20. The silicon carbide power semiconductor device of claim 1, wherein the well region of silicon carbide does not contact the plug region of silicon carbide.

11. A silicon carbide power semiconductor device comprising:

a first silicon carbide layer having a first conductivity type;

a source region in the first silicon carbide layer and having the first conductivity type, the source region having a higher carrier concentration than a carrier concentration of the first silicon carbide layer and extending to a first surface of the first silicon carbide layer, the source region having dopants of the first conductivity type and dopants of a second conductivity type opposite the first conductivity type;

a buried region of silicon carbide of the second conductivity type in the first silicon carbide layer adjacent a bottom portion of the source region and at a depth in the first silicon carbide layer greater than a depth of the source region;

a well region of silicon carbide of the second conductivity type in the first silicon carbide layer on a first side of the source region and extending toward the first surface of the first silicon carbide layer;

a plug region of silicon carbide of the second conductivity type on a second side of the source region, opposite the first side of the source region, and extending to the first face of the first silicon carbide layer;

a gate oxide on the first silicon carbide layer, the well region and the source region;

a gate contact on the gate oxide;

a source contact on the plug region and the source region; and

a drain contact on the first silicon carbide layer opposite the first surface of the first silicon carbide layer.

12. The silicon carbide power semiconductor device of claim 11, wherein the first conductivity type is n-type and the second conductivity type is p-type.

13. The silicon carbide power semiconductor device of claim 11, further comprising threshold adjustment regions of first conductivity type silicon carbide in the first silicon carbide layer and extending on coplanar surfaces of the source region and the well region and being disposed between the well region and the first face of the first layer of silicon carbide.

14. The silicon carbide power semiconductor device of claim 13, wherein the threshold adjustment regions extend to a depth of from about 0.01 μ

m to about 0.5 μ

m into the first layer of silicon carbide and have a carrier concentration of from about 10¹⁵ to about 10¹⁹ cm<sup>−

3</sup>.

15. The silicon carbide power semiconductor device of claim 11, further comprising a first silicon carbide epitaxial layer on the first face of the first silicon carbide layer between the gate oxide and the first silicon carbide layer.

16. The silicon carbide power semiconductor device of claim 15, wherein the first silicon carbide epitaxial layer has a thickness of from about 6 μ

m to about 200 μ

m and a carrier concentration of from about 1×

10¹⁴ to about 5×

10¹⁶ cm<sup>−

3</sup>.

17. The silicon carbide power semiconductor device of claim 15, further comprising threshold adjustment regions of first conductivity type silicon carbide in the first silicon carbide layer and extending from the source region, the threshold adjustment regions being disposed between the well region and the first face of the first layer of silicon carbide.

18. The silicon carbide power semiconductor device of claim 17, wherein the threshold adjustment regions extend to a depth of from about 0.01 μ

m to about 0.5 μ

m into the first layer of silicon carbide and have a carrier concentration of from about 10¹⁵ to about 10¹⁹ cm<sup>−

3</sup> and wherein the first silicon carbide epitaxial layer has a thickness of from about 6 μ

m to about 200 μ

m and a carrier concentration of from about 1×

10¹⁴ to about 5×

10¹⁶ cm<sup>−

3</sup>.

19. The silicon carbide power semiconductor device of claim 11, further comprising a second layer of silicon carbide of the first conductivity type disposed between the first layer of silicon carbide and the drain contact, the second layer of silicon carbide having a higher carrier concentration than the first layer of silicon carbide.

21. The silicon carbide power semiconductor device of claim 11, wherein the well region of silicon carbide does not contact the plug region of silicon carbide.