Methods of fabricating silicon carbide devices including multiple floating guard ring edge termination
View Patent ↗Edge termination for silicon carbide devices has a plurality of concentric floating guard rings in a silicon carbide layer that are adjacent and spaced apart from a silicon carbide-based semiconductor junction. An insulating layer, such as an oxide, is provided on the floating guard rings and a silicon carbide surface charge compensation region is provided between the floating guard rings and is adjacent the insulating layer. Methods of fabricating such edge termination are also provided.
1. A method of fabricating an edge termination structure for a silicon carbide semiconductor device, comprising:
forming a plurality of spaced apart concentric floating guard rings in a silicon carbide layer that surround at least a portion of a silicon carbide-based semiconductor junction;
forming an insulating layer on the floating guard rings; and
forming a silicon carbide surface charge compensation region between the floating guard rings and adjacent the insulating layer, wherein the surface charge compensation region has a dopant concentration such that the surface of the surface charge compensation region adjacent the insulating layer is partially depleted by surface charges of the insulating layer and fully depleted when a reverse bias lower than the blocking voltage of the device is applied to the device.
2. The method of claim 1 , wherein forming a plurality of floating guard rings comprises forming a plurality of floating guard rings that extend a first distance into the silicon carbide layer and wherein forming a silicon carbide surface charge compensation region comprises forming a surface charge compensation region that extends a second distance into the silicon carbide layer, the second distance being less than the first distance.
3. The method of claim 1 , wherein the surface charge compensation region is lighter doped than the guard rings.
4. The method of claim 1 , wherein the surface charge compensation region extends between adjacent ones of the floating guard rings but does not extend completely between two adjacent floating guard rings.
5. The method of claim 1 , wherein forming a silicon carbide surface charge compensation region comprises implanting regions in the silicon carbide layer.
6. The method of claim 1 , wherein the surface charge compensation region comprises a plurality of surface charge compensation regions.
7. The method of claim 1 , wherein the surface charge compensation region has a dose charge of from about 1×10 12 to about 7×10 12 cm −2 .
8. The method of claim 1 , wherein the surface charge compensation region extends a distance of from about 0.1 μm to about 2.0 μm into the silicon carbide layer.
9. The method of claim 1 , wherein the surface charge compensation region does not extend completely between two adjacent floating guard rings and to provide a gap of from about 0.1 μm to about 2.0 μm between the surface charge compensation region and one of the two adjacent floating guard rings.
10. The method of claim 1 , wherein the floating guard rings are uniformly spaced, non-uniformly spaced and/or combinations of uniformly and non-uniformly spaced.
11. The method of claim 1 , wherein the floating guard rings extend from about 0.1 μm to about 2.0 μm into the silicon carbide layer.
12. The method of claim 1 , wherein the floating guard rings have a spacing of from about 0.1 μm to about 10 μm.
13. The method of claim 1 , wherein the plurality of floating guard rings comprises from about 2 to about 100 guard rings.
14. The method of claim 1 , wherein the floating guard rings extend a distance of from about 2 μm to about 1 mm from the semiconductor junction of the device.
15. The method of claim 1 , wherein the floating guard rings have a dopant concentration of from about 1×10 18 cm −3 to about 1×10 20 cm −3 .
16. The method of claim 1 , wherein the silicon carbide layer is an n-type silicon carbide layer and the floating guard rings and surface charge compensation region are p-type silicon carbide.