Trench isolation without grooving
View Patent ↗A method and structure to form shallow trench isolation regions without trench oxide grooving is provided. In particular, a method includes a two-step oxide process in which an oxide liner lines the inside surface of a trench and the trench is filled with a bulk oxide layer, preferably using a high density plasma chemical vapor deposition (HDP-CVD) process. The oxide liner and the bulk oxide layer are formed to have similar etch rates. Thus, when etching the oxide liner and the bulk oxide layer between stack structures, a common dielectric top surface is formed that is substantially planar and without grooves.
1. A trench isolation structure, comprising:
two stack structures over a substrate;
a trench in the substrate between the two stack structures;
an oxide liner over the trench, wherein the oxide liner includes a thermal oxide layer and an in-situ oxide layer; and
a bulk oxide layer over the oxide liner, wherein the etch rate of the oxide liner is within about 10% of the etch rate of the bulk oxide layer.
2. The structure of claim 1 , wherein the oxide liner is formed to have a refractive index within about 5% of the refractive index of the bulk oxide layer.
3. The structure of claim 2 , wherein the refractive index of the oxide liner is about 1.46.
4. The structure of claim 1 , wherein the oxide liner comprises a rapid thermal oxide layer.
5. The structure of claim 1 , wherein a top surface of the bulk oxide layer and the oxide liner is below a top surface of the two stack structures.
6. The structure of claim 1 , wherein the stack structures are comprised of silicon nitride and polysilicon.
7. The structure of claim 1 , wherein the thermal oxide layer has a thickness of about 35 Å.
8. The structure of claim 1 , wherein the in-situ oxide layer has a thickness between about 100 Å and about 300 Å.
9. The structure of claim 1 , further comprising a tunnel oxide layer over the substrate and under the two stack structures.
10. The structure of claim 9 , wherein the tunnel oxide layer has a thickness of about 90 Å.
11. A trench isolation structure, comprising:
two stack structures over a substrate;
a trench in the substrate between the two stack structures;
a thermal oxide layer over the trench;
an in-situ oxide layer over the thermal oxide layer and over the two stack structures; and
a bulk oxide layer over the in-situ oxide layer, wherein the etch rate of the thermal oxide layer and the in-situ oxide layer is substantially similar to the etch rate of the bulk oxide layer.
12. The structure of claim 11 , wherein the thermal oxide layer and the in-situ oxide layer have a refractive index within about 5% of the refractive index of the bulk oxide layer.
13. The structure of claim 12 , wherein the refractive index of the thermal oxide layer and the in-situ oxide layer is about 1.46.
14. The structure of claim 11 , wherein a top surface of the bulk oxide layer, the thermal oxide layer, and the in-situ oxide layer is below a top surface of the two stack structures.
15. The structure of claim 11 , wherein the stack structures are comprised of silicon nitride and polysilicon.
16. The structure of claim 11 , wherein the thermal oxide layer has a thickness of about 35 Å.
17. The structure of claim 11 , wherein the in-situ oxide layer has a thickness between about 100 Å and about 300 Å.
18. The structure of claim 11 , further comprising a tunnel oxide layer over the substrate and under the two stack structures.
19. The structure of claim 18 , wherein the tunnel oxide layer has a thickness of about 90 Å.