Fully depleted SOI transistor with a buried ferroelectric layer in back-gate
Provided are techniques for generating fully depleted silicon on insulator (SOI) transistor with a ferroelectric layer. The techniques include forming a first multi-layer wafer comprising a semiconductor layer and a buried oxide layer, wherein the semiconductor layer is formed over the buried oxide layer. The techniques also including forming a second multi-layer wafer comprising the ferroelectric layer, and bonding the first multi-layer wafer to the second multi-layer wafer, wherein the bonding comprises a coupling between the buried oxide layer and the second multi-layer wafer.
1. A method of fabricating a semiconductor device, the method comprising:
forming a first multi-layer wafer comprising a semiconductor layer and a buried oxide layer;
wherein the semiconductor layer is formed over the buried oxide layer, wherein the buried dielectric layer is epitaxially grown on the first multi-layer wafer;
forming a second multi-layer wafer comprising a ferroelectric layer and a back-gate contact layer, wherein the ferroelectric layer is formed on top of the back-gate contact layer, wherein the ferroelectric layer comprises hafnium oxide, wherein the back-gate contact layer is used to control a switching voltage of a device on the first multi-layer wafer; and
bonding the first multi-layer wafer to the second multi-layer wafer;
wherein the bonding comprises the buried oxide layer of the first multi-layer wafer is bonded in direct contact with a polycrystalline layer of the second multi-layer wafer, wherein the polycrystalline layer of the second multi-layer wafer directly contacts the ferroelectric layer of the second multi-layer wafer.
2. The method of claim 1 further comprising forming a conducting layer on the ferroelectric layer of the second multi-layer wafer.
3. The method of claim 2 , wherein the bonding includes coupling the buried oxide layer of the first multi-layer wafer to the conducting layer of the second multi-layer wafer.
4. The method of claim 2 , wherein the conducting layer comprises an amorphous silicon layer, and, responsive to the bonding, the amorphous silicon layer transitions to the polycrystalline layer.
5. The method of claim 1 further comprising forming a gate stack over the semiconductor layer of the first multi-layer wafer.
6. The method of claim 1 further comprising:
forming a source, a drain and a channel region in the semiconductor layer;
wherein the gate stack is over the channel region;
wherein the gate stack comprises a gate insulator and a metal gate;
wherein the gate insulator is coupled to the semiconductor layer and the metal gate is coupled to the gate insulator.
7. The method of claim 1 , wherein the buried oxide layer has a thickness of approximately 50 nanometers.