III-nitride semiconductor device with trench structure
View Patent ↗A III-nitride trench device has a vertical conduction region with an interrupted conduction channel when the device is not on, providing an enhancement mode device. The trench structure may be used in a vertical conduction or horizontal conduction device. A gate dielectric provides improved performance for the device by being capable of withstanding higher electric field or manipulating the charge in the conduction channel. A passivation of the III-nitride material decouples the dielectric from the device to permit lower dielectric constant materials to be used in high power applications.
1. A method for forming a III-nitride field effect device, comprising:
depositing alternating layers of a first III-nitride material and layers of a second III-nitride material to form a multilayer stack having a 2DEG at each of a plurality of heterointerfaces between the layers of the first III-nitride material and the layers of the second III-nitride material;
providing a plurality of doped III-nitride layers over said multilayer stack, said plurality of doped III-nitride layers forming at least one PN junction over said multilayer stack;
performing a self-passivation in a surface of the III-nitride layer before deposition of a gate dielectric.
2. The method according to claim 1 , wherein the passivation is performed with a nitrogen plasma anneal.
3. The method according to claim 1 , wherein the performing of the self-passivation further comprises:
depositing an encapsulant material containing nitrogen on a surface to be passivated; and
annealing the encapsulant material.
4. The method according to claim 1 , wherein the self-passivation is performed with a photo-electro-chemical etch.
5. The method according to claim 1 , wherein the device is a bi-directional device.
6. The method according to claim 1 , wherein the device is a nominally ON device.
7. The method according to claim 1 , wherein the device is a nominally OFF device.
8. The method according to claim 1 , wherein the device is a vertical conduction device.
9. The method according to claim 1 , wherein the gate dielectric material comprises Gd oxide.
10. The method according to claim 1 , wherein the gate dielectric material comprises Mg oxide.
11. A method for forming a III-nitride field effect device, comprising:
doping a layer under a first gate dielectric material using the first gate dielectric material as a mask, the first gate dielectric material situated over a surface protection layer;
removing the first gate dielectric material and self-passivating a channel region of the III-nitride field effect device; and
depositing and patterning a second gate dielectric material over the self-passivated channel region to form a gate dielectric.
12. The method according to claim 11 , wherein the second gate dielectric material comprises zirconium oxide.
13. The method according to claim 11 , wherein the second gate dielectric material comprises a lanthanoid group oxide.
14. The method according to claim 11 , wherein the second gate dielectric material comprises diamond.
15. The method according to claim 11 , wherein the second gate dielectric material comprises a piezoelectric or a pyroelectric material.
16. The method according to claim 11 , further comprising forming a trench in the III-nitride field effect device such that the channel region is located on a sidewall of the trench.
17. The method according to claim 16 , wherein the second gate dielectric material comprises Gd oxide or Mg oxide.
18. The method according to claim 11 , comprising depositing the surface protection layer to form a thin, nitrogen rich layer prior to the depositing of the first gate dielectric over the surface protection layer.
19. The method according to claim 11 , wherein the performing of the surface further comprises:
depositing an encapsulant material containing nitrogen on a surface to be passivated; and
annealing the encapsulant material.
20. The method according to claim 11 , wherein the surface passivation is performed with a photo-electro-chemical etch.