III-N device structures and methods
A III-N device is described with a III-N layer, an electrode thereon, a passivation layer adjacent the III-N layer and electrode, a thick insulating layer adjacent the passivation layer and electrode, a high thermal conductivity carrier capable of transferring substantial heat away from the III-N device, and a bonding layer between the thick insulating layer and the carrier. The bonding layer attaches the thick insulating layer to the carrier. The thick insulating layer can have a precisely controlled thickness and be thermally conductive.
1. A method of making a III-N device comprising:
forming on a substrate a first structure comprising a III-N semiconductor layer having an electrode, an insulating layer on a side of the III-N semiconductor layer opposite the substrate, and a first bonding layer over the insulating layer;
forming a second structure, wherein the forming of the second structure comprises applying a second bonding layer to a high thermal conductivity carrier; and
after forming the first and second structures, bonding the second bonding layer of the second structure to the first bonding layer of the first structure.
2. The method of claim 1 , further comprising the step of removing the entire substrate to expose a surface of the III-N semiconductor layer.
3. The method of claim 2 , further comprising depositing a passivation layer on the surface of the III-N semiconductor layer.
4. The method of claim 3 , wherein the passivation layer is selected from the group consisting of silicon nitride, aluminum nitride, silicon dioxide, alumina, a polymeric dielectric, and an organic dielectric.
5. The method of claim 3 , further comprising forming a via through the passivation layer.
6. The method of claim 5 , further comprising depositing a conductive material in the via.
7. The method of claim 1 , wherein the insulating layer is at least 1 micron thick.
8. The method of claim 1 , wherein the high thermal conductivity carrier is at least 100 microns thick.
9. The method of claim 1 , wherein the high thermal conductivity carrier comprises aluminum nitride.
10. The method of claim 1 , further comprising forming an aperture through the substrate, wherein the aperture is through an entire thickness of the substrate but not through an entire thickness of the III-N semiconductor layer.
11. A method of forming a III-N device, comprising:
forming a III-N material on a substrate, the substrate having a thickness, wherein the III-N material contacts the substrate, and a crystalline structure of the III-N material adjacent to the substrate at least partially conforms to or is at least partially determined by a crystalline structure of the substrate;
forming an electrode adjacent the III-N material on a side of the III-N material opposite the substrate;
forming an aperture through the entire thickness of the substrate; and
depositing an insulating material in the aperture, the insulating material contacting the III-N material; wherein
the aperture is opposite the electrode, and the insulating material extends over a side of the substrate opposite the III-N layer.
12. The method of claim 11 , wherein the aperture is through the entire thickness of the substrate but not through an entire thickness of the III-N material.
13. The method of claim 11 , the III-N material comprising a III-N channel layer and a III-N barrier layer, wherein a two-dimensional electron gas is in the III-N channel layer near an interface between the III-N channel layer and the III-N barrier layer.
14. The method of claim 11 , wherein the insulating material comprises silicon nitride, aluminum nitride, silicon dioxide, or alumina.
15. The method of claim 11 , wherein the insulating material comprises a polymeric or organic dielectric.
16. A method of forming a III-N device, comprising:
providing a substrate, the substrate having a thickness;
forming a III-N material on the substrate, the III-N material comprising a III-N channel layer and a III-N barrier layer, wherein a two-dimensional electron gas is in the III-N channel layer near an interface between the III-N channel layer and the III-N barrier layer;
forming an electrode adjacent the III-N material on a side of the III-N material opposite the substrate;
forming an aperture through the entire thickness of the substrate; and
depositing an additional layer in the aperture, the additional layer contacting the III-N material; wherein
the additional layer comprises an element selected from the group consisting of silicon nitride, aluminum nitride, alumina, a polymeric dielectric, and an organic dielectric.
17. The method of claim 16 , wherein the aperture is below and around the electrode.
18. The method of claim 16 , wherein the electrode contacts the two-dimensional electron gas.
19. The method of claim 16 , wherein the electrode is a gate, and the III-N device is a transistor.
20. The method of claim 16 , wherein the channel layer has a thickness, and the aperture is through the entire thickness of the substrate but not through the entire thickness of the channel layer.
21. The method of claim 16 , wherein the additional layer comprises a polymeric dielectric or an organic dielectric.