Silicon carbide power devices with self-aligned source and well regions and methods of fabricating same

1. A method of fabricating a silicon carbide power device comprising:

successively patterning a single mask layer to provide a first window for formation of a source region of a first conductivity type and a buried silicon carbide region of a second conductivity type opposite the first conductivity type and a second window for formation of a second conductivity type well region in a first conductivity type silicon carbide layer.

2. The method of claim 1 , further comprising:

forming the source region and the buried silicon carbide region utilizing a first window of the single mask layer; and then

forming the well region utilizing a second window of the mask layer, the second window being provided by a subsequent patterning of the single mask layer having the first window.

3. The method of claim 1 , wherein the first conductivity type is n-type silicon carbide and the second conductivity type is p-type silicon carbide and wherein the buried silicon carbide region comprises a buried p-type silicon carbide region and the well region comprises a p-well region.

4. A method of fabricating a silicon carbide power device comprising:

successively patterning 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 the first conductivity type and a second conductivity type well region in a first conductivity type silicon carbide layer;

wherein the first conductivity type is n-type silicon carbide and the second conductivity type is p-type silicon carbide and wherein the buried silicon carbide region comprises a buried p-type silicon carbide region and the well region comprises a p-well region; and

wherein successively patterning a mask layer, forming the source region and the buried p-type silicon carbide region and forming the p-well region comprise:

forming the mask layer on a first surface of the first n-type silicon carbide layer;

patterning the mask layer to provide a first implantation mask, the first implantation mask having at least one window corresponding to the source region of the silicon carbide power device; then

implanting n-type dopants in the first n-type silicon carbide layer utilizing the first implantation mask having the at least one window to provide an n-type source region, the n-type source region extending to the first surface of the first n-type silicon carbide layer and having a higher carrier concentration than the first n-type silicon carbide layer;

implanting p-type dopants in the first n-type silicon carbide layer utilizing the first implantation mask having the at least one window to provide the buried p-type region adjacent the n-type source region, the buried p-type region being disposed at a depth in the first n-type silicon carbide layer greater than a depth of the n-type source region; then

etching the first implantation mask to provide a second implantation mask, the second implantation mask having at least one window corresponding to the p-well region and corresponding to the at least one window of the first implantation mask widened by the etch; and then

implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide the p-well region, the p-well region extending to the p-type buried region.

5. A method of fabricating a silicon carbide power device comprising:

successively patterning a mask layer to provide a first window for formation of a source region of a first conductivity type and buried silicon carbide region of a second conductivity type opposite the first conductivity type and a second window for formation of a second conductivity type well region in a first conductivity type silicon carbide layer;

wherein the first conductivity type is n-type silicon carbide and the second conductivity type is p-type silicon carbide and wherein the buried silicon carbide region comprises a buried p-type silicon carbide region and the well region comprises a p-well region; and

wherein successively patterning a mask layer to provide windows for formation of a source region, a buried p-type silicon carbide region and a p-well region comprises successively patterning a mask layer to provide windows for formation of a source region, a buried p-type silicon carbide region, a p-well region and a threshold adjustment region in a first n-type silicon carbide layer, the method further comprising forming the threshold adjustment region utilizing a third window of the mask layer, the third window being provided by a subsequent etch of the mask layer having the second window.

6. A method of fabricating a silicon carbide power device comprising:

successively patterning 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 the first conductivity type and a second conductivity type well region in a first conductivity type silicon carbide layer;

wherein the first conductivity type is n-type silicon carbide and the second conductivity type is p-type silicon carbide and wherein the buried silicon carbide region comprises a buried p-type silicon carbide region and the well region comprises a p-well region; and

wherein successively patterning a mask layer, forming the source region and the buried p-type silicon carbide region and forming the p-well region comprise:

forming the mask layer on a first n-type silicon carbide layer;

patterning the mask layer to provide a first implantation mask, the first implantation mask having at least one window corresponding to the source region of the silicon carbide power device; then

implanting n-type dopants in the first n-type silicon carbide layer utilizing the first implantation mask having the at least one window to provide an n-type source region, the n-type source region extending to a first surface of the first n-type silicon carbide layer and having a higher carrier concentration than the first n-type silicon carbide layer;

implanting p-type dopants in the first n-type silicon carbide layer utilizing the first implantation mask having the at least one window to provide the buried p-type region adjacent the n-type source region, the p-type dopants being implanted utilizing a higher implantation energy than an implant energy utilized to implant the n-type dopants in the first n-type silicon carbide layer utilizing the first implantation mask to provide an n-type source region; then

etching the first implantation mask to provide a second implantation mask, the second implantation mask having at least one window corresponding to the p-well region and corresponding to the at least one window of the first implantation mask widened by the etch; and then

implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide the p-well region, the p-type dopants being implanted utilizing an implantation energy such that the p-well region extends to the p-type buried region.

7. The method of claim 6 , wherein implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide the p-well region comprises implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide a carrier concentration of the p-well region that is less than a carrier concentration of the buried p-type silicon carbide layer.

8. The method of claim 6 , wherein implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide the p-well region is followed by:

etching the second implantation mask to provide a third implantation mask, the third implantation mask having at least one window corresponding to a threshold adjustment region and corresponding to the at least one window of the second implantation mask widened by the etch; and then

implanting n-type dopants in the first n-type silicon carbide layer utilizing the third implantation mask to provide the threshold adjustment region.

9. The method of claim 8 , wherein implanting n-type dopants in the first n-type silicon carbide layer utilizing the third implantation mask to provide the threshold adjustment region comprises implanting n-type dopants in the first n-type silicon carbide layer utilizing the third implantation mask to a depth of from about 0.01 to about 0.5 μm into the first n-type silicon carbide layer.

10. The method of claim 8 , further comprising:

removing the third implantation mask;

forming a fourth implantation mask, the fourth implantation mask patterned to provide a window exposing the first surface of the first n-type silicon carbide layer inside the source region;

implanting p-type dopants utilizing the fourth implantation mask to provide a p-type silicon carbide plug region, the plug region extending into the first n-type silicon carbide layer to contact the p-type buried region;

forming a gate oxide on the first surface of the first n-type silicon carbide layer;

forming a gate contact on the gate oxide;

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

forming a drain contact on the first n-type silicon carbide layer opposite the first surface.

11. The method of claim 10 , further comprising forming a second n-type silicon carbide layer on a surface of the first n-type silicon carbide layer opposite the first surface, the second n-type silicon carbide layer having a carrier concentration higher than a carrier concentration of the first n-type silicon carbide layer.

12. The method of claim 8 , wherein implanting n-type dopants in the first n-type silicon carbide layer utilizing the third implantation mask to provide the threshold adjustment region is followed by:

removing the third implantation mask; and

forming an n-type silicon carbide epitaxial layer on the first surface of the first n-type silicon carbide layer.

13. The method of claim 12 , wherein forming an n-type silicon carbide epitaxial layer is preceded by the steps of:

forming a fourth implantation mask, the fourth implantation mask patterned to provide a window exposing a portion of the n-type silicon carbide epitaxial layer inside the source region;

implanting p-type dopants utilizing the fourth implantation mask to provide a p-type silicon carbide plug region, the plug region extending into the first n-type silicon carbide layer to contact the p-type buried region; and

activating the implanted dopants; and

wherein forming an n-type silicon carbide epitaxial layer is followed by the steps of:

forming a gate oxide on n-type silicon carbide epitaxial layer;

forming a gate contact on the gate oxide;

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

forming a drain contact on the first n-type silicon carbide layer opposite the first surface.

14. The method of claim 13 , further comprising forming a second n-type silicon carbide layer on a surface of the first n-type silicon carbide layer apposite the first surface, the second n-type silicon carbide layer having a carrier concentration higher than a carrier concentration of the first n-type silicon carbide layer.

15. The method of claim 6 , wherein implanting p-type dopants in the first n-type silicon carbide layer utilizing the second implantation mask to provide the p-well region is followed by:

removing the second implantation mask; and

forming an n-type silicon carbide epitaxial layer on the first surface of the first n-type silicon carbide layer.

16. The method of claim 15 , wherein forming an n-type silicon carbide epitaxial layer is preceded by the steps of:

forming a third implantation mask, the third implantation mask patterned to provide a window exposing a portion of the n-type silicon carbide epitaxial layer inside the source region;

implanting p-type dopants utilizing the third implantation mask to provide a p-type silicon carbide plug region, the plug region extending into the first n-type silicon carbide layer to contact the p-type buried region; and

activating the implanted dopants; and

wherein forming an n-type silicon carbide epitaxial layer is followed by the steps of:

forming a gate oxide on n-type silicon carbide epitaxial layer;

forming a gate contact on the gate oxide;

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

forming a drain contact on the first n-type silicon carbide layer opposite the first surface.

17. The method of claim 16 , further comprising forming a second n-type silicon carbide layer on a surface of the first n-type silicon carbide layer opposite the first surface, the second n-type silicon carbide layer having a carrier concentration higher than a carrier concentration of the first n-type silicon carbide layer.