Shallow trench isolation structures
View Patent ↗Shallow trench isolation structures are provided for use with UTBB (ultra-thin body and buried oxide) semiconductor substrates, which prevent defect mechanisms from occurring, such as the formation of electrical shorts between exposed portions of silicon layers on the sidewalls of shallow trench of a UTBB substrate, in instances when trench fill material of the shallow trench is subsequently etched away and recessed below an upper surface of the UTBB substrate.
1. A semiconductor device, comprising:
a semiconductor substrate comprising a first silicon layer, a second silicon layer, and a buried oxide layer disposed between the first silicon layer and the second silicon layer;
a high-k gate dielectric layer formed on the first silicon layer;
a shallow trench isolation structure formed in the semiconductor substrate, the shallow trench isolation structure comprising:
a shallow trench formed through the first silicon layer, the buried oxide layer and partially through the second silicon layer;
a first liner disposed directly on exposed surfaces of the first and second silicon layers in the shallow trench;
a second liner conformally lining the shallow trench, wherein the second liner covers the first liner and covers an exposed surface of the buried oxide layer in the shallow trench; and
a trench fill material disposed in the shallow trench, wherein the first second liner is formed of a material having etch selectivity with regard to the trench fill material.
2. The semiconductor device of claim 1 , wherein the second liner comprises a high-k dielectric liner.
3. The semiconductor device of claim 1 , wherein the first liner is formed of oxynitride.
4. The semiconductor device of claim 1 , wherein the first liner comprises a thermal oxide layer that is grown on the exposed surfaces of the first and second silicon layers in the shallow trench.
5. The semiconductor device of claim 4 , wherein the thermal oxide comprises silicon dioxide.
6. The semiconductor device of claim 1 , wherein the second liner conformally lines an entire sidewall and bottom surface of the shallow trench.
7. The semiconductor device of claim 1 , wherein an upper sidewall portion of the shallow trench isolation structure comprises a void region between the second liner and an upper surface of the first silicon layer, wherein the void region isolates the second liner from the high-k gate dielectric layer formed on the first silicon layer.
8. The semiconductor device of claim 1 , wherein a thickness of the buried oxide layer is in a range of about 5 nm to about 75 nm.
9. The semiconductor device of claim 1 , wherein the trench fill material comprises an oxide material.
10. The semiconductor device of claim 1 , wherein the second liner comprises hafnium silicate.
11. The semiconductor device of claim 1 , wherein the second liner comprises hafnium oxide.
12. The semiconductor device of claim 1 , wherein the first second liner comprises Ti 0 2 .
13. The semiconductor device of claim 1 , wherein a thickness of the first silicon layer is about 5 nm to about 25 nm.
14. The semiconductor device of claim 1 , wherein the semiconductor substrate comprises a silicon-on-insulator (SOI) substrate.
15. The semiconductor device of claim 1 , wherein a portion of the second liner disposed near an upper region of the shallow trench contacts the high-k gate dielectric layer.