InP-based transistor fabrication
View Patent ↗Methods of forming structures that include InP-based materials, such as a transistor operating as an inversion-type, enhancement-mode device. A dielectric layer may be deposited by ALD over a semiconductor layer including In and P. A channel layer may be formed above a buffer layer having a lattice constant similar to a lattice constant of InP, the buffer layer being formed over a substrate having a lattice constant different from a lattice constant of InP.
1. A method of fabricating a transistor, the method comprising:
providing a crystalline substrate having a first lattice constant substantially different from a lattice constant of InP;
providing a non-crystalline mask above the substrate, the mask including an opening having sidewalls that extend above the substrate by a height;
providing within the opening a crystalline buffer layer having a second lattice constant substantially lattice-matched to InP, the buffer layer having a height less than the mask opening sidewall height, the buffer layer height being sufficient to permit defects arising from the lattice mismatch to exit the buffer layer at the mask opening sidewalls;
providing a channel layer above the buffer layer, a portion of the channel layer being lower than a top surface of the mask, the channel layer comprising a crystalline material, the crystalline material comprising an InP-based material;
defining a source region, a drain region, and a channel region of a transistor in the channel layer; and
providing a gate above the channel layer.
2. The method of claim 1 wherein the substrate is a silicon substrate.
3. The method of claim 1 wherein the mask comprises SiO 2 .
4. The method of claim 1 wherein the buffer layer comprises a III-V material.
5. The method of claim 1 wherein the buffer layer comprises InP.
6. The method of claim 1 , wherein the source region and the drain region are defined in the InP-based material, the channel region being defined between the source region and the drain region, the gate being provided above the channel region, and further comprising depositing a gate dielectric over the channel region by atomic layer deposition (ALD), wherein at least a portion of the gate dielectric is disposed between the gate and the channel region and the transistor operates as an inversion-type, enhancement-mode device.
7. The method of claim 6 wherein the gate dielectric comprises at least one of a group II material or a transition metal.
8. The method of claim 7 wherein the gate dielectric comprises aluminum.
9. The method of claim 7 wherein the gate dielectric comprises hafnium.
10. The method of claim 1 wherein the source and drain regions are further disposed above the channel layer.
11. The method of claim 1 wherein the channel layer comprises a strained region.
12. The method of claim 1 wherein the channel layer comprises at least one of InSb, InGaAs, or InAs.
13. The method of claim 1 wherein the channel layer comprises a plurality of substantially lattice-matched layers.
14. The method of claim 1 wherein the transistor is a MOSFET.
15. The method of claim 1 wherein the transistor is a HEMT.
16. The method of claim 1 , wherein the providing the gate comprises:
depositing by ALD, above at least a portion of the channel layer, a dielectric layer comprising hafnium; and
providing a conductive layer over at least a portion of the dielectric layer, wherein the dielectric layer is disposed between the channel layer and the conductive layer.