Surface passivation of GaN devices in epitaxial growth chamber
View Patent ↗The present invention relates to passivation of a gallium nitride (GaN) structure before the GaN structure is removed from an epitaxial growth chamber. The GaN structure includes one or more structural epitaxial layers deposited on a substrate, and the passivation layer deposited on the structural epitaxial layers. In general, the passivation layer is a dielectric material deposited on the GaN structure that serves to passivate surface traps on the surface of the structural epitaxial layers. Preferably, the passivation layer is a dense, thermally deposited silicon nitride passivation layer.
1. A method of growing a gallium nitride (GaN) epitaxial structure comprising:
a) depositing one or more structural epitaxial layers including a GaN buffer layer on a substrate; and
b) depositing a thermally assisted silicon nitride passivation layer as a surface layer for passivating surface traps on the one or more structural epitaxial layers before the GaN epitaxial structure is removed from an associated growth chamber, wherein active devices are formed in the one or more structural epitaxial layers; wherein the depositing the passivation layer occurs after the depositing the one or more structural epitaxial layers step while within the growth chamber.
2. The method of claim 1 further comprising:
a) etching a source and drain region of the passivation layer;
b) forming a source contact on the one or more structural epitaxial layers in the etched source region of the passivation layer;
c) forming a gate contact on the passivation layer; and
d) forming a drain contact on the one or more structural epitaxial layers in the etched drain region of the passivation layer,
thereby forming a metal-insulator-semiconductor field effect transistor.
3. The method of claim 2 wherein the source and drain regions of the passivation layer are etched using a wet chemical etch.
4. The method of claim 1 wherein the thermally assisted silicon nitride passivation layer is the top layer of the gallium nitride epitaxial structure.
5. The method of claim 1 wherein the depositing the passivation layer occurs immediately after the depositing the one or more structural epitaxial layers step while within the growth chamber.
6. The method of claim 1 wherein the depositing the passivation layer step is a thermally activated deposition process.
7. The method of claim 1 wherein the depositing the one or more structural epitaxial layers step comprises depositing a transitional layer on the substrate.
8. The method of claim 7 wherein the depositing the one or more structural epitaxial layers step further comprises depositing the GaN buffer layer on the transitional layer.
9. The method of claim 7 wherein the depositing the one or more structural epitaxial layers step further comprises depositing an aluminum gallium nitride (AlGaN) Schottky layer on the GaN buffer layer.
10. The method of claim 9 wherein the depositing the one or more structural epitaxial layers step further comprises depositing a GaN termination layer on the AlGaN Schottky layer.
11. The method of claim 7 wherein the depositing the one or more structural epitaxial layers step comprises depositing an aluminum nitride (AlN) sub-buffer layer on the transitional layer.
12. The method of claim 11 wherein the depositing the one or more structural epitaxial layers step further comprises depositing the GaN buffer layer on the sub-buffer layer.
13. The method of claim 12 wherein the depositing the one or more structural epitaxial layers step further comprises depositing an aluminum gallium nitride (AlGaN) Schottky layer on the GaN buffer layer.
14. The method of claim 13 wherein the depositing the one or more structural epitaxial layers step further comprises depositing a GaN termination layer on the AlGaN Schottky layer.
15. The method of claim 1 further comprising:
a) etching source, gate, and drain regions of the passivation layer;
b) forming a source contact on the one or more structural epitaxial layers in the etched source region of the passivation layer;
c) forming a gate contact on the one or more structural epitaxial layers in the etched gate region of the passivation layer; and
d) forming a drain contact on the one or more structural epitaxial layers in the etched drain region of the passivation layer,
thereby forming a high electron mobility transistor.
16. The method of claim 15 wherein the source, gate, and drain regions of the passivation layer are etched using a wet chemical etch.
17. The method of claim 15 wherein the source and drain regions are etched using a dry chemical etch and the gate region is etched using a wet chemical etch.