Methods of forming reverse side engineered III-nitride devices
Group III-nitride devices are described that include a stack of III-nitride layers, passivation layers, and conductive contacts. The stack includes a channel layer with a 2DEG channel, a barrier layer and a spacer layer. One passivation layer directly contacts a surface of the spacer layer on a side opposite to the channel layer and is an electrical insulator. The stack of III-nitride layers and the first passivation layer form a structure with a reverse side proximate to the first passivation layer and an obverse side proximate to the barrier layer. Another passivation layer is on the obverse side of the structure. Defected nucleation and stress management layers that form a buffer layer during the formation process can be partially or entirely removed.
1. A method of forming a device, comprising:
providing a silicon substrate;
forming a stack of III-nitride layers on the silicon substrate, wherein the forming of the stack includes forming a channel layer with a 2DEG channel therein, the stack of III-nitride layers having an obverse face opposite to the silicon substrate;
removing an entirety of the silicon substrate, wherein the removing comprises exposing a reverse face of the stack;
depositing a passivation layer that forms part of the device, the passivation layer comprising dielectric material on the exposed reverse face of the stack of III-nitride layers, in direct contact with the stack of III-nitride layers; and
depositing a conductive layer in contact with the passivation layer, such that the passivation layer is sandwiched between the conductive layer and the stack of III-nitride layers.
2. The method of claim 1 , further comprising attaching the obverse face of the stack to a carrier wafer prior to the removing of the entirety of the silicon substrate.
3. The method of claim 1 , wherein the forming of the stack of III-nitride layers comprises forming a nucleation layer on the silicon substrate.
4. The method of claim 3 , further comprising removing the nucleation layer prior to depositing the passivation layer.
5. The method of claim 1 , further comprising
forming, on the obverse face, conductive contacts that are electrically connected to the 2DEG channel.
6. The method of claim 1 , wherein:
the stack of III-nitride layers includes a barrier layer on a first side of the channel layer and a spacer layer on a second side of the channel layer;
the spacer layer includes an etch stop layer; and
the removing comprises etching to the etch stop layer.
7. The method of claim 6 , further comprising fabricating one of a diode or a transistor in the stack of III-nitride layers.
8. The method of claim 6 , wherein the dielectric material of the passivation layer comprises silicon nitride, silicon dioxide, silicon oxynitride, silicon oxide, or alumina.
9. The method of claim 6 , wherein the dielectric material of the passivation layer comprises polyimide, benzocyclobutene, SUB, or an organic dielectric material.
10. The method of claim 6 , further comprising depositing an insulator material on the obverse face.