Recessed termination structures and methods of fabricating electronic devices including recessed termination structures
View Patent ↗An electronic device includes a drift region, a Schottky contact on a surface of the drift region, and an edge termination structure in the drift region adjacent the Schottky contact. The edge termination structure includes a recessed region that is recessed from the surface of the drift region by a distance d that may be about 0.5 microns.
1. An electronic device, comprising:
a drift region;
a Schottky contact on a surface of the drift region;
an edge termination in the drift region adjacent the Schottky contact, wherein the edge termination comprises a recessed region that is recessed from the surface of the drift region by a distance d and an edge termination structure in the recessed region; and
an upper guard ring at the surface of the drift region beneath the Schottky contact and a plurality of lower guard rings at a surface of the recessed region, and wherein the upper guard ring and the plurality of lower guard rings have a second conductivity type that is opposite a first conductivity type of the drift region, wherein the lower guard rings comprise rings of the second conductivity type that are electrically isolated from one another and that surround an active region defined by the Schottky contact.
2. The electronic device of claim 1 , farther comprising a plurality of junction barrier Schottky regions at the surface of the drift region and in contact with the Schottky contact, wherein the plurality of junction barrier Schottky regions have a second conductivity type that is opposite the first conductivity type.
3. The electronic device of claim 1 , wherein the distance d is about 0.2 microns to about 1 micron.
4. The electronic device of claim 1 , wherein the distance d is about 0.4 microns to about 0.8 microns.
5. The electronic device of claim 1 , wherein the distance d is about 0.5 microns.
6. The electronic device of claim 1 , further comprising a sidewall in the drift region between the active region and the recessed region, and wherein one of the plurality of lower guard rings is located at a base of the sidewall adjacent the Schottky contact.
7. The electronic device of claim 2 , wherein the distance d is greater than a depth of the junction barrier Schottky regions from the surface of the drift region into the drift region.
8. The electronic device of claim 1 , wherein the drift region comprises silicon carbide.
9. The electronic device of claim 8 , wherein the drift region comprises silicon carbide having a polytype of 2H, 4H, 6H, 3C, and/or 15R.
10. The electronic device of claim 1 , having an avalanche rating in excess of 780 mJ/cm 2 , wherein avalanche rating is defined as V BR ×I R ×t pulse /chip area, wherein V BR is the breakdown voltage of the device, I R is the reverse current rating of the device and t pulse is a minimum duration of a current pulse that results in device failure.
11. The electronic device of claim 10 , wherein the avalanche rating is greater than 1000 mJ/cm 2 .
12. The electronic device of claim 10 , wherein the avalanche rating is greater than 1200 mJ/cm 2 .
13. The electronic device of claim 10 , wherein the avalanche rating is greater than 1500 mJ/cm 2 .
14. The electronic device of claim 1 , wherein the electronic device has a theoretical avalanche breakdown voltage based on a doping level and thickness of the drift region of the device, and having a leakage voltage that is less than 100 V less than the theoretical avalanche breakdown voltage, wherein the leakage voltage is defined as a reverse voltage on the device that results in a leakage current of at least 100 μA/cm 2 .
15. The electronic device of claim 14 , wherein, the electronic device has a leakage voltage that is less than 25 V less than the theoretical avalanche breakdown voltage of the device.
16. The electronic device of claim 1 , wherein the edge termination structure is configured to experience avalanche breakdown before a reverse breakdown of the Schottky contact when a reverse bias is applied to the device.
17. The electronic device of claim 16 , further comprising a junction barrier Schottky region in the drift region adjacent the Schottky contact.
18. The electronic device of claim 6 , wherein the upper guard ring is merged with the one of the lower guard rings at the base of the sidewall.
19. The electronic device of claim 1 , further comprising a lightly doped region having the second conductivity type at a surface of the recessed region, wherein the plurality of guard rings extend into the lightly doped region.
20. An electronic device, comprising:
a drift region having a first conductivity type;
an active region including a junction barrier Schottky region at a surface of the drift region having a second conductivity type opposite the first conductivity type wherein a p-n junction between the junction barrier Schottky region and the drift region is configured to sustain a voltage when the electronic device is reverse biased;
an edge termination in the drift region adjacent the active region, wherein the edge termination comprises a recessed region that is recessed from the surface of the drift region by a distance d and an edge termination structure in the recessed region; and
an upper guard ring in the active region at the surface of the drift region inside the edge termination;
wherein the edge termination structure comprises a plurality of guard rings at a surface of the recessed region, wherein the plurality of guard rings have a second conductivity type that is opposite a first conductivity type of the drift region and wherein the guard rings comprise rings of the second conductivity type that are electrically isolated from one another and that surround the active region; and
wherein the distance d is greater than a depth of the junction barrier Schottky region from the surface of the drift region into the drift region.
21. The electronic device of claim 20 , wherein the device has a leakage voltage that is less than 25 V less than a theoretical avalanche breakdown voltage of the device, wherein the leakage voltage is defined as a reverse voltage on the device that results in a leakage current of at least 100 μA/cm 2 .
22. The electronic device of claim 20 , wherein the electronic device comprises a MOSFET, and wherein the plurality of doped regions comprise wells that define unit cells of the device.
23. The electronic device of claim 20 , wherein the electronic device comprises a Schottky diode, and wherein the active region comprises a plurality of junction barrier regions that are configured to sustain a voltage when a reverse bias is applied to the device.