Monolithic bidirectional silicon carbide switching devices
View Patent ↗A monolithic bidirectional switching device includes a drift layer having a first conductivity type and having an upper surface, and first and second vertical metal-oxide semiconductor (MOS) structures at the upper surface of the drift layer. The drift layer provides a common drain for the first and second vertical MOS structures. The first and second vertical MOS structures are protected by respective first and second edge termination structures at the upper surface of the drift layer. A monolithic bidirectional switching device according to further embodiments includes a vertical MOS structure at the upper surface of the drift layer, and a diode at the upper surface of the drift layer. The drift layer provides a drain for the vertical MOS structure and a cathode for the diode, and the vertical MOS structure and the diode are protected by respective first and second edge termination structures.
1. A monolithic bidirectional switching device, comprising:
a drift layer having a first conductivity type and having an upper surface; and
first and second vertical metal-oxide semiconductor (MOS) structures at the upper surface of the drift layer, wherein the drift layer provides a common drain for the first and second vertical MOS structures, and wherein the first and second vertical MOS structures are surrounded by respective first and second edge termination structures at the upper surface of the drift layer.
2. The monolithic bidirectional switching device of claim 1 , wherein the first edge termination structure comprises a first plurality of guard rings in the upper surface of the drift layer, the first plurality of guard rings having a second conductivity type opposite the first conductivity type, and wherein the second edge termination structure comprises a second plurality of guard rings in the upper surface of the drift layer, the second plurality of guard rings having the second conductivity type.
3. The monolithic bidirectional switching device of claim 1 , further comprising:
a substrate having the first conductivity type, wherein the drift layer is provided on a first surface of the substrate; and
a metal layer on a second surface of the substrate opposite the first surface.
4. The monolithic bidirectional switching device of claim 1 , wherein the first MOS structure comprises:
a first well region at the upper surface of the drift layer, the first well region having a second conductivity type that is opposite the first conductivity type;
a first source region in the first well region, the first source region having the first conductivity type;
a first gate insulator on the upper surface of the drift layer and defining a channel region in the first well region adjacent the first source region;
a first gate contact on the first gate insulator; and
a first source contact on the first source region and on the first well region.
5. The monolithic bidirectional switching device of claim 4 , wherein the first source contact forms an ohmic contact with the first source region and the first well region.
6. The monolithic bidirectional switching device of claim 4 , wherein the second MOS structure comprises:
a second well region at the upper surface of the drift layer, the second well region having the second conductivity type;
a second source region in the second well region, the second source region having the first conductivity type;
a second gate insulator on the upper surface of the drift layer and defining a channel region in the second well region adjacent the second source region;
a second gate contact on the second gate insulator; and
a second source contact on the second source region and on the second well region.
7. The monolithic bidirectional switching device of claim 6 , further comprising:
a third well region at the surface of the drift layer, the third well region spaced apart from the first well region and defining a first vertical current flow region in the drift layer between the first well region and the third well region;
a third source region in the third well region;
a third source contact on the third source region and the third well region;
a fourth well region at the surface of the drift layer, the fourth well region spaced apart from the second well region and defining a second vertical current flow region in the drift layer between the second well region and the fourth well region;
a fourth source region in the fourth well region; and
a fourth source contact on the fourth source region and the fourth well region.
8. The monolithic bidirectional switching device of claim 1 , wherein the drift layer comprises silicon carbide.
9. A packaged electronic device, comprising:
a package housing;
a monolithic bidirectional switching device within the package housing, the monolithic bidirectional switching device comprising a drift layer having a first conductivity type and having an upper surface and first and second vertical metal-oxide semiconductor (MOS) structures at the upper surface of the drift layer, wherein the drift layer provides a common drain for the first and second vertical MOS structures, and wherein the first and second vertical MOS structures are surrounded by respective first and second edge termination structures at the upper surface of the drift layer; and
a plurality of electrical leads coupled to the monolithic bidirectional switching device and extending from the housing.
10. A monolithic bidirectional switching device, comprising:
a drift layer having a first conductivity type and having an upper surface; and
first and second metal oxide semiconductor (MOS) structures at the upper surface of the drift layer, wherein the drift layer provides a common drain for the first and second vertical MOS structures;
a first source contact coupled to the first MOS structure; and
a second source contact coupled to the second MOS structure;
wherein the first MOS structure comprises a first body diode having an anode and a cathode, wherein the anode of the first body diode is coupled to the first source contact;
wherein the second MOS structure comprises a second body diode having an anode and a cathode, wherein the anode of the second body diode is coupled to the second source contact, and wherein the cathodes of the first and second body diodes are coupled to the common drain; and
wherein the first and second source contacts are electrically isolated from one another and first and second gate contacts are electrically isolated from one another to thereby provide bidirectional blocking capability by the first MOS structure and the second MOS structure.
11. The monolithic bidirectional switching device of claim 10 , wherein the first and second MOS structures are surrounded by respective first and second edge termination structures at the upper surface of the drift layer.
12. The monolithic bidirectional switching device of claim 11 , wherein the first edge termination structure comprises a first plurality of guard rings in the upper surface of the drift layer, the first plurality of guard rings having a second conductivity type opposite the first conductivity type, and wherein the second edge termination structure comprises a second plurality of guard rings in the upper surface of the drift layer, the second plurality of guard rings having the second conductivity type.
13. The monolithic bidirectional switching device of claim 10 , further comprising:
a substrate having the first conductivity type, wherein the drift layer is provided on a first surface of the substrate; and
a metal layer on a second surface of the substrate opposite the first surface.
14. The monolithic bidirectional switching device of claim 10 , wherein the first MOS structure comprises:
a first well region at the upper surface of the drift layer, the first well region having a second conductivity type that is opposite the first conductivity type;
a first source region in the first well region, the first source region having the first conductivity type;
a first gate insulator on the upper surface of the drift layer and defining a channel region in the first well region adjacent the first source region; and
the first gate contact on the first gate insulator;
wherein the first source contact is on the first source region and on the first well region.
15. The monolithic bidirectional switching device of claim 14 , wherein the first source contact forms an ohmic contact with the first source region and the first well region.
16. The monolithic bidirectional switching device of claim 14 , wherein the second MOS structure comprises:
a second well region at the upper surface of the drift layer, the second well region having the second conductivity type;
a second source region in the second well region, the second source region having the first conductivity type;
a second gate insulator on the upper surface of the drift layer and defining a channel region in the second well region adjacent the second source region; and
the second gate contact on the second gate insulator;
wherein the second source contact is on the second source region and on the second well region.
17. The monolithic bidirectional switching device of claim 16 , further comprising:
a third well region at the surface of the drift layer, the third well region spaced apart from the first well region and defining a first vertical current flow region in the drift layer between the first well region and the third well region;
a third source region in the third well region;
a third source contact on the third source region and the third well region;
a fourth well region at the surface of the drift layer, the fourth well region spaced apart from the second well region and defining a second vertical current flow region in the drift layer between the second well region and the fourth well region;
a fourth source region in the fourth well region; and
a fourth source contact on the fourth source region and the fourth well region.
18. The monolithic bidirectional switching device of claim 10 , wherein the drift layer comprises silicon carbide.