Method and system for fabricating floating guard rings in GaN materials
View Patent ↗A method for fabricating an edge termination structure includes providing a substrate having a first surface and a second surface and a first conductivity type, forming a first GaN epitaxial layer of the first conductivity type coupled to the first surface of the substrate, and forming a second GaN epitaxial layer of a second conductivity type opposite to the first conductivity type. The second GaN epitaxial layer is coupled to the first GaN epitaxial layer. The method also includes implanting ions into a first region of the second GaN epitaxial layer to electrically isolate a second region of the second GaN epitaxial layer from a third region of the second GaN epitaxial layer. The method further includes forming an active device coupled to the second region of the second GaN epitaxial layer and forming the edge termination structure coupled to the third region of the second GaN epitaxial layer.
1. A method for fabricating an edge termination structure, the method comprising:
providing a substrate of a first conductivity type, the substrate having a first surface and a second surface;
forming a first GaN epitaxial layer of the first conductivity type coupled to the first surface of the substrate;
forming a second GaN epitaxial layer of a second conductivity type opposite to the first conductivity type, the second GaN epitaxial layer being coupled to the first GaN epitaxial layer;
implanting ions into a first region of the second GaN epitaxial layer to electrically isolate a second region of the second GaN epitaxial layer from a third region of the second GaN epitaxial layer; and
forming an active device coupled to the second region of the second GaN epitaxial layer;
wherein the third region of the second GaN epitaxial layer comprises an edge termination structure.
2. The method of claim 1 further comprising forming a first metallic structure electrically coupled to the second surface of the substrate.
3. The method of claim 2 further comprising forming a second metallic structure electrically coupled to a portion of the second region of the second GaN epitaxial layer, wherein the second metallic structure comprises an Ohmic contact to the portion of the second region of the second GaN epitaxial layer.
4. The method of claim 3 wherein the second metallic structure is further electrically coupled to the edge termination structure.
5. The method of claim 4 wherein forming the first metallic structure is performed before forming the second metallic structure.
6. The method of claim 1 wherein the substrate is characterized by a first n-type dopant concentration, the first GaN epitaxial layer is characterized by a second n-type dopant concentration less than the first n-type dopant concentration, and the second GaN epitaxial layer is characterized by a p-type dopant concentration greater than the second n-type dopant concentration and less than the first n-type dopant concentration.
7. The method of claim 1 further comprising forming a metallic structure electrically coupled to a portion of the first GaN epitaxial layer, wherein the metallic structure comprises a Schottky contact to the portion of the first GaN epitaxial layer.
8. The method of claim 7 further comprising:
forming a dielectric layer coupled to the edge termination structure and the metallic structure;
removing a portion of the dielectric layer to expose a portion of the metallic structure; and
forming a field plate coupled to the exposed portion of the metallic structure.
9. The method of claim 1 further comprising forming a metallic field plate coupled to the edge termination structure.
10. The method of claim 1 wherein the edge termination structure circumscribes the active device.
11. A method of fabricating a vertical power device structure, the method comprising:
forming an epitaxial structure by:
providing a III-nitride substrate of a first conductivity type characterized by a first dopant concentration;
forming a first III-nitride epitaxial layer of the first conductivity type coupled to a first surface of the III-nitride substrate; and
forming a second III-nitride epitaxial layer of a second conductivity type coupled to the first III-nitride epitaxial layer, wherein the second III-nitride epitaxial layer has a surface opposing the first III-nitride epitaxial layer;
defining regions of the epitaxial structure by implanting ions into the surface of the second epitaxial layer to form an implantation region of the epitaxial structure, wherein the implantation region electrically isolates a device region of the epitaxial structure from an edge termination region of the epitaxial structure;
forming one or more active devices using at least the device region of the epitaxial structure; and
forming an edge termination structure using at least the edge termination region of the epitaxial structure.
12. The method of claim 11 further comprising forming a Schottky metallic structure coupled to the first epitaxial layer.
13. The method of claim 12 wherein the metallic structure is further coupled to the edge termination structure.
14. The method of claim 11 further comprising forming a metallic field plate coupled to the edge termination structure.
15. The method of claim 11 wherein the edge termination structure circumscribes the one or more active devices.
16. The method of claim 11 wherein the first III-nitride epitaxial layer is characterized by a second dopant concentration less than the first dopant concentration.
17. The method of claim 11 wherein forming the edge termination structure comprises forming three or more edge termination elements with predetermined spaces between each of the three or more edge termination elements, wherein:
a first spacing of the predetermined spaces is located closer to the one or more active devices than a second spacing of the predetermined spaces; and
a width of the first spacing is smaller than a width of the second spacing.