USRE49167EActiveUtility

Passivation structure for semiconductor devices

Assignee: WOLFSPEED INCPriority: Oct 4, 2012Filed: Nov 12, 2019Granted: Aug 9, 2022

Est. expiryOct 4, 2032(~6.2 yrs left)· nominal 20-yr term from priority

Inventors:Van Mieczkowski Jonathan D. Young Qingchun Zhang John Williams Palmour

H10P 14/662H10W 72/983H10D 8/051H10D 64/64H10D 18/60H10D 12/441H10D 62/8325H10D 62/126H10D 62/106H10D 8/60H01L 21/045H01L 29/872H01L 29/0692H01L 29/7395H01L 29/1608H01L 21/022H01L 29/47H01L 29/744H01L 29/0619H01L 29/6606

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Claims

Abstract

A Schottky diode is disclosed that includes a silicon carbide substrate, a silicon carbide drift layer, a Schottky contact, and a passivation structure. The silicon carbide drift layer provides an active region and an edge termination region about the active region. The Schottky contact has sides and a top extending between the two sides and includes a Schottky layer over the active region and an anode contact over the Schottky layer. The passivation structure covers the edge termination region, the sides of the Schottky contact, and at least a portion of the top of the Schottky contact. The passivation structure includes a first silicon nitride layer, a silicon dioxide layer over the first silicon nitride layer, and a second silicon nitride layer over the silicon dioxide layer.

Claims

exact text as granted — not AI-modified

What is claimed is:

1. A Schottky diode comprising:
a silicon carbide substrate;
a silicon carbide drift layer over the silicon carbide substrate and providing an active region and an edge termination region about the active region;
a Schottky contact having sides and a top extending between the sides and comprising a Schottky layer over the active region and an anode contact over the Schottky layer; and
a passivation structure comprising a first silicon nitride layer, a silicon dioxide layer over the first silicon nitride layer, and a second silicon nitride layer over the silicon dioxide layer, wherein the first silicon nitride layer, the silicon dioxide layer, and the second silicon nitride layer are plasma enhanced chemical vapor deposition layers such that a thickness of the first silicon nitride layer is greater than a thickness of the second silicon nitride layer and the passivation structure covers the edge termination region, the sides of the Schottky contact, and at least a portion of the top of the Schottky contact.

2. The Schottky diode of claim 1 further comprising an oxide layer between the passivation structure and the silicon carbide drift layer and extending outward from the sides of the Schottky contact over the edge termination region.

3. The Schottky diode of claim 2 wherein the oxide layer does not cover the top of the Schottky contact and portions of the sides of the Schottky contact that extend above the oxide layer.

4. The Schottky diode of claim 3 wherein the oxide layer is a thermally grown silicon dioxide layer.

5. The Schottky diode of claim 2 wherein the oxide layer is a thermally grown silicon dioxide layer.

6. The Schottky diode of claim 1 further comprising a cathode contact on a bottom side of the silicon carbide substrate opposite the silicon carbide drift layer.

7. The Schottky diode of claim 1 wherein the Schottky contact further comprises a tantalum barrier layer between the anode contact and the Schottky layer.

8. The Schottky diode of claim 1 further comprising an encapsulation layer over the passivation structure.

9. The Schottky diode of claim 8 wherein the encapsulation layer is a polyimide layer.

10. The Schottky diode of claim 1 wherein the thickness of the second silicon nitride layer is greater than a thickness of the silicon dioxide layer.

11. The Schottky diode of claim 1 wherein the thickness of the first silicon nitride layer is between about 6400 and 9600 Angstroms, a thickness of the silicon dioxide layer is between about 900 and 1100 Angstroms, and the thickness of the second silicon nitride layer is between about 2400 and 3600 Angstroms.

12. The Schottky diode of claim 11 wherein an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15, an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5, and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

13. The Schottky diode of claim 1 wherein an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15, an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5, and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

14. The Schottky diode of claim 1 further comprising an oxide layer that extends outward from the sides of the Schottky contact over the edge termination region, and wherein
for the passivation structure, the first silicon nitride layer is directly on the oxide layer, the silicon dioxide layer is directly on the first silicon nitride layer, and the second silicon nitride layer is directly on the silicon dioxide layer.

15. The Schottky diode of claim 14 wherein the oxide layer is a thermally grown silicon dioxide layer that does not cover the top of the Schottky contact and portions of the sides of the Schottky contact that extend above the silicon dioxide layer.

16. The Schottky diode of claim 1 wherein the Schottky diode has a rated reverse breakdown voltage and can operate at 80% of the rated reverse breakdown voltage, at 85% humidity, and at 85 Celsius for at least 1000 hours without failing.

17. The Schottky diode of claim 1 wherein the Schottky diode has a rated reverse breakdown voltage of at least 600 V.

18. A method for fabricating a Schottky diode comprising:
providing a silicon carbide substrate with a silicon carbide drift layer over the silicon carbide substrate, the silicon carbide drift layer having an active region and an edge termination region about the active region;
forming a Schottky contact over the active region, the Schottky contact having sides and a top extending between the sides and comprising a Schottky layer over the active region and an anode contact over the Schottky layer; and
forming a passivation structure comprising a first silicon nitride layer, a silicon dioxide layer over the first silicon nitride layer, and a second silicon nitride layer over the silicon dioxide layer, wherein the first silicon nitride layer, the silicon dioxide layer, and the second silicon nitride layer are plasma enhanced chemical vapor deposition layers such that a thickness of the first silicon nitride layer is greater than a thickness of the second silicon nitride layer and the passivation structure covers the edge termination region, the sides of the Schottky contact, and at least a portion of the top of the Schottky contact.

19. The method of claim 18 wherein the first silicon nitride layer, the silicon dioxide layer, and the second silicon nitride layer are successively formed during a single plasma enhanced chemical vapor deposition process.

20. The method of claim 18 further comprising forming an oxide layer that extends outward from the sides of the Schottky contact over the edge termination region prior to forming the passivation structure.

21. The method of claim 20 wherein the oxide layer does not cover the top of the Schottky contact and portions of the sides of the Schottky contact that extend above the oxide layer.

22. The method of claim 21 wherein the oxide layer is a thermally grown silicon dioxide layer.

23. The method of claim 20 wherein the oxide layer is a thermally grown silicon dioxide layer.

24. The method of claim 18 further comprising forming a cathode contact on a bottom side of the silicon carbide substrate opposite the silicon carbide drift layer.

25. The method of claim 24 wherein the thickness of the first silicon nitride layer is greater than a thickness of the silicon dioxide layer.

26. The method of claim 18 wherein the thickness of the first silicon nitride layer is between about 6400 and 9600 Angstroms, a thickness of the silicon dioxide layer is between about 900 and 1100 Angstroms, and the thickness of the second silicon nitride layer is between about 2400 and 3600 Angstroms.

27. The method of claim 26 wherein an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15, an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5, and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

28. The method of claim 18 wherein the Schottky diode has a rated reverse breakdown voltage and can operate at 80% of the rated reverse breakdown voltage, at 85% humidity, and at 85 Celsius for at least 1000 hours without failing.

29. The method of claim 18 wherein the Schottky diode has a rated reverse breakdown voltage of at least 600 V.

30. The method of claim 18 further comprising forming a polyimide layer over the passivation structure.

31. The method of claim 18 further comprising forming an oxide layer that extends outward from the sides of the Schottky contact over the edge termination region prior to forming the passivation structure, and wherein the first silicon nitride layer is directly on the oxide layer, the silicon dioxide layer is directly on the first silicon nitride layer, and the second silicon nitride layer is directly on the silicon dioxide layer.

32. The method of claim 18 wherein the oxide layer is a thermally grown silicon dioxide layer that does not cover the top of the Schottky contact and portions of the sides of the Schottky contact that extend above the silicon dioxide layer.

33. The method of claim 18 wherein the thickness of the second silicon nitride layer is greater than a thickness of the silicon dioxide layer.

34. The method of claim 18 wherein an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15, an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5, and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

35. The method of claim 18 further comprising forming a tantalum barrier layer between the anode contact and the Schottky layer.

36. A semiconductor device comprising:
a silicon carbide substrate; a silicon carbide drift layer over the silicon carbide substrate; a contact on the silicon carbide drift layer, the contact having sides and a top extending between the sides; and a passivation structure covering the sides of the contact and at least a portion of the top of the contact, the passivation structure comprising a first silicon nitride layer, a silicon dioxide layer on the first silicon nitride layer, and a second silicon nitride layer on the silicon dioxide layer, wherein:
the first silicon nitride layer, the silicon dioxide layer, and the second silicon nitride layer are plasma enhanced chemical vapor deposition layers; and
a thickness of the first silicon nitride layer is greater than a thickness of the second silicon nitride layer.

37. The semiconductor device of claim 36 wherein the silicon carbide drift layer provides an active region and an edge termination region about the active region.

38. The semiconductor device of claim 37 wherein the passivation structure covers the edge termination region.

39. The semiconductor device of claim 38 further comprising an oxide layer between the passivation structure and the silicon carbide drift layer, the oxide layer extending outward from the sides of the contact over the edge termination region.

40. The semiconductor device of claim 39 wherein the oxide layer does not cover the top of the contact and portions of the sides of the contact that extend above the oxide layer.

41. The semiconductor device of claim 40 wherein the oxide layer is a thermally grown silicon dioxide layer.

42. The semiconductor device of claim 39 wherein the oxide layer is a thermally grown silicon dioxide layer.

43. The semiconductor device of claim 36 further comprising an additional contact on the silicon carbide substrate opposite the drift layer.

44. The semiconductor device of claim 36 further comprising an encapsulation layer over the passivation structure.

45. The semiconductor device of claim 44 wherein the encapsulation layer is a polyimide layer.

46. The semiconductor device of claim 36 wherein the thickness of the second silicon nitride layer is greater than a thickness of the silicon dioxide layer.

47. The semiconductor device of claim 46 wherein:
the thickness of the first silicon nitride layer is between about 6400 and 9600 Angstroms; the thickness of the silicon dioxide layer is between about 900 and 1100 Angstroms; and the thickness of the second silicon nitride layer is between about 2400 and 3600 Angstroms.

48. The semiconductor device of claim 47 wherein:
an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15; an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5; and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

49. The semiconductor device of claim 36 wherein:
an index of refraction for the first silicon nitride layer is between about 1.95 and 2.15; an index of refraction for the silicon dioxide layer is between about 1.45 and 1.5; and an index of refraction for the second silicon nitride layer is between about 1.95 and 2.15.

50. The semiconductor device of claim 38 further comprising an oxide layer that extends outward from the sides of the contact over the edge termination region, wherein the first silicon nitride layer is directly on the oxide layer, the silicon dioxide layer is directly on the first silicon nitride layer, and the second silicon nitride layer is directly on the silicon dioxide layer.

51. The semiconductor device of claim 50 wherein the oxide layer is a thermally grown silicon dioxide layer that does not cover the top of the contact and portions of the sides of the contact that extend above the silicon dioxide layer.

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