Granted Patent B2

US 8,445,917 · App. 12/408,167 · Granted May 21, 2013

Abstract

Claims (32)

1. A bidirectional transient voltage suppression device, comprising:

a silicon carbide layer having a first conductivity type and having a first surface and a second surface opposite the first surface; and

first and second silicon carbide diodes on the silicon carbide layer, wherein each of the first and second silicon carbide diodes includes a first heavily doped silicon carbide layer having a second conductivity type opposite the first conductivity type, a second heavily doped silicon carbide layer having the first conductivity type, and an ohmic contact on the first heavily doped silicon carbide layer, wherein the silicon carbide layer is electrically connected to the first and second silicon carbide diodes and provides a common reference for the first and second silicon carbide diodes,

wherein the second heavily doped silicon carbide layer is between the silicon carbide layer and the first heavily doped silicon carbide layer,

wherein the first and second silicon carbide diodes comprise mesas on the silicon carbide layer, and

wherein the mesas include the first heavily doped silicon carbide layer and the second heavily doped silicon carbide layer.

2. The bidirectional transient voltage suppression device of claim 1 , wherein the silicon carbide layer has a thickness less than about 200 μm.

3. The bidirectional transient voltage suppression device of claim 1 , wherein the silicon carbide layer has a doping concentration of about 5×10 18 cm −3 or more.

4. The bidirectional transient voltage suppression device of claim 1 , wherein the first heavily doped silicon carbide layers are p-type with a doping concentration of about 5×10 18 cm −3 or more.

5. The bidirectional transient voltage suppression device of claim 1 ,

wherein the second heavily doped silicon carbide layers form a respective Zener junction with the first heavily doped silicon carbide layer.

6. The bidirectional transient voltage suppression device of claim 5 , wherein the second heavily doped silicon carbide layer is n-type with a doping concentration of about 1×10 19 cm −3 or more.

7. The bidirectional transient voltage suppression device of claim 1 , further comprising an ohmic contact layer on the silicon carbide layer opposite the first and second silicon carbide diodes.

8. The bidirectional transient voltage suppression device of claim 1 , wherein at least one of the first heavily doped silicon carbide layers has an increased doping concentration near the ohmic contact thereon.

9. The bidirectional transient voltage suppression device of claim 1 , wherein the first heavily doped silicon carbide layers comprise first heavily doped silicon carbide epitaxial layers on the silicon carbide layer.

10. The bidirectional transient voltage suppression device of claim 9 , wherein the silicon carbide layer comprises an epitaxial silicon carbide layer.

11. The bidirectional transient voltage suppression device of claim 10 , wherein the mesas extend completely through the first heavily doped silicon carbide epitaxial layers and into but not completely through the silicon carbide layer.

12. The bidirectional transient voltage suppression device of claim 10 , wherein the mesas extend completely through the first heavily doped silicon carbide epitaxial layers and completely through the silicon carbide layer.

13. The bidirectional transient voltage suppression device of claim 1 , wherein the mesas each have a cross sectional area of about 0.25 mm 2 or more.

14. The bidirectional transient voltage suppression device of claim 1 , wherein the silicon carbide layer comprises a bulk silicon carbide substrate, and wherein the mesas extend completely through the first heavily doped silicon carbide layers and into the silicon carbide substrate.

15. The bidirectional transient voltage suppression device of claim 1 , wherein each of the first and second diodes has a breakdown voltage that is less than 20V.

16. The bidirectional transient voltage suppression device of claim 1 , wherein each of the first and second diodes has a negative breakdown voltage temperature coefficient.

17. The bidirectional transient voltage suppression device of claim 1 , wherein the first and second silicon carbide diodes comprise Zener diodes.

18. A bidirectional transient voltage suppression device, comprising:

a silicon carbide layer having a first conductivity type and having a first surface and a second surface opposite the first surface;

first and second silicon carbide diodes on the silicon carbide layer, wherein each of the first and second silicon carbide diodes comprises a first heavily doped silicon carbide epitaxial layer having a second conductivity type opposite the first conductivity type, and a second heavily doped silicon carbide epitaxial layer having the first conductivity type,

wherein the silicon carbide layer is conductively connected to the first and second silicon carbide diodes and provides a common reference for the first and second silicon carbide diodes, and

first and second ohmic contacts, respectively, on the heavily doped silicon carbide epitaxial layers of the first and second silicon carbide diodes opposite the silicon carbide layer,

wherein the first and second silicon carbide diodes comprise mesas on the silicon carbide layer, and

wherein the mesas include the first heavily doped silicon carbide epitaxial layer and the second heavily doped silicon carbide epitaxial layer.

19. The bidirectional transient voltage suppression device of claim 18 , wherein each of the first and second diodes has a breakdown voltage that is less than 20V.

20. The bidirectional transient voltage suppression device of claim 18 , wherein the first and second silicon carbide diodes comprise Zener diodes.

Assignments (6)