Edge termination for power semiconductor devices and related fabrication methods
A power semiconductor device includes semiconductor layer structure comprising a semiconductor drift region of a first conductivity type and an edge termination region comprising a plurality of guard rings of a second conductivity type. The guard rings extend into a surface of the semiconductor drift region. The guard rings respectively comprise a first portion adjacent the surface and a second portion spaced from the surface, where the first portion is wider than the second portion. Related devices and fabrication methods are also discussed.
1. A power semiconductor device, comprising:
a semiconductor layer structure comprising a semiconductor drift region of a first conductivity type and an edge termination region comprising a plurality of guard rings of a second conductivity type,
wherein one or more of the guard rings extend in the semiconductor drift region to a depth of greater than about 1 micrometers (μm) relative to a surface of the semiconductor layer structure, and two or more of the guard rings are laterally separated from one another by a spacing of less than about 3 μm.
2. The power semiconductor device of claim 1 , wherein the one or more of the guard rings respectively comprise a first portion adjacent the surface and a second portion spaced from the surface, wherein the first portion is wider than the second portion.
3. The power semiconductor device of claim 2 , wherein the second portion comprises a higher concentration of dopants of the second conductivity type than the first portion.
4. The power semiconductor device of claim 2 , wherein the first portion extends into the surface to a first depth, and wherein the second portion extends through the first portion to a second depth that is greater than the first depth.
5. The power semiconductor device of claim 2 , wherein the one or more of the guard rings respectively comprise a third portion comprising a higher concentration of dopants of the second conductivity type than the second portion.
6. The power semiconductor device of claim 5 , wherein the third portion is narrower than the first portion.
7. The power semiconductor device of claim 5 , wherein the third portion is confined within the first portion in two or more dimensions.
8. The power semiconductor device of claim 2 , wherein the one or more of the guard rings respectively comprise a sidewall comprising a step difference between the first and second portions.
9. The power semiconductor device of claim 4 , wherein the semiconductor layer structure further comprises an active region comprising a plurality of well regions of the second conductivity type in the semiconductor drift region, wherein the well regions extend to the first depth.
10. The power semiconductor device of claim 9 , wherein the active region further comprises a plurality of shielding patterns comprising a higher concentration of dopants of the second conductivity type than the well regions, wherein the shielding patterns extend to the second depth.
11. The power semiconductor device of claim 2 , wherein the spacing is substantially uniform between the first portions.
12. The power semiconductor device of claim 1 , wherein the depth is about 1 μm to about 3 μm, and wherein the spacing is about 0.5 lam to about 3 μm.
13. The power semiconductor device of claim 1 , wherein the one or more of the guard rings respectively comprise a first width adjacent the surface and a second width spaced from the surface, and wherein a ratio of the first width to the second width is about 0.95 to about 2.
14. A power semiconductor device, comprising:
a semiconductor layer structure comprising a semiconductor drift region of a first conductivity type and an edge termination region comprising a plurality of guard rings of a second conductivity type in the semiconductor drift region,
wherein one or more of the guard rings respectively comprise a first portion adjacent a surface of the semiconductor layer structure and a second portion spaced from the surface of the semiconductor layer structure, wherein the second portion comprises a higher concentration of dopants of the second conductivity type than the first portion.
15. The power semiconductor device of claim 14 , wherein the first portion is wider than the second portion.
16. The power semiconductor device of claim 15 , wherein the first portion extends into the surface to a first depth, and wherein the second portion extends through the first portion and to a second depth that is greater than the first depth.
17. The power semiconductor device of claim 15 , wherein the one or more of the guard rings respectively comprise a third portion comprising a higher concentration of dopants of the second conductivity type than the second portion, wherein the third portion is narrower than the first portion.
18. The power semiconductor device of claim 14 , wherein two or more of the guard rings are laterally separated from one another by a spacing, wherein the spacing is substantially uniform between the first portions.
19. A power semiconductor device, comprising:
a semiconductor layer structure comprising a semiconductor drift region of a first conductivity type and an edge termination region comprising a plurality of guard rings of a second conductivity type in the semiconductor drift region,
wherein one or more of the guard rings respectively comprise a first portion adjacent a surface of the semiconductor layer structure, a second portion spaced from the surface of the semiconductor layer structure, and a sidewall, wherein the sidewall of a respective guard ring comprises a step difference between the first and second portions.
20. The power semiconductor device of claim 19 , wherein the second portion comprises a higher concentration of dopants of the second conductivity type than the first portion, and wherein the step difference is defined at an interface between the first and second portions.
21. The power semiconductor device of claim 20 , wherein the first portion is wider than the second portion.
22. The power semiconductor device of claim 20 , wherein the first portion extends into the surface to a first depth, and wherein the second portion extends through the first portion to a second depth that is greater than the first depth.
23. The power semiconductor device of claim 22 , wherein the semiconductor layer structure further comprises an active region comprising a plurality of well regions of the second conductivity type in the semiconductor drift region, wherein the well regions extend to the first depth.
24. The power semiconductor device of claim 23 , wherein the active region further comprises a plurality of shielding patterns comprising a higher concentration of dopants of the second conductivity type than the well regions, wherein the shielding patterns extend to the second depth.
25. A power semiconductor device, comprising:
a semiconductor layer structure comprising a semiconductor drift region of a first conductivity type and an edge termination region comprising a plurality of guard rings of a second conductivity type in the semiconductor drift region,
wherein one or more of the guard rings respectively comprise a first width adjacent a surface of the semiconductor layer structure and a second width spaced from the surface of the semiconductor layer structure, and wherein a ratio of the first width to the second width is about 0.95 to about 2.
26. The power semiconductor device of claim 25 , wherein the one or more of the guard rings respectively comprise a first portion comprising the first width between outermost boundaries thereof and a second portion comprising the second width between outermost boundaries thereof, wherein the first portion is wider than the second portion.
27. The power semiconductor device of claim 26 , wherein the second portion comprises a higher concentration of dopants of the second conductivity type than the first portion.
28. The power semiconductor device of claim 26 , wherein the first portion extends into the surface to a first depth, and wherein the second portion extends through the first portion to a second depth that is greater than the first depth.
29. The power semiconductor device of claim 26 , wherein the one or more of the guard rings respectively comprise a third portion comprising a higher concentration of dopants of the second conductivity type than the second portion, wherein the third portion is narrower than the first portion.
30. The power semiconductor device of claim 26 , wherein the one or more of the guard rings respectively comprise a sidewall comprising a step difference between the first and second portions.
31. The power semiconductor device of claim 25 , wherein the ratio is about 0.95 to about 1.05.
32. The power semiconductor device of claim 25 , wherein the ratio is about 0.99 to about 1.01.