Semiconductor device and method for fabricating the same
A method for fabricating semiconductor device includes the steps of: providing a material layer having a contact pad therein; forming a dielectric layer on the material layer and the contact pad; forming a doped oxide layer on the dielectric layer; forming an oxide layer on the doped oxide layer; performing a first etching process to remove part of the oxide layer, part of the doped oxide layer, and part of the dielectric layer to form a first contact hole; performing a second etching process to remove part of the doped oxide layer to form a second contact hole; and forming a conductive layer in the second contact hole to form a contact plug.
1. A method for fabricating semiconductor device, comprising:
providing a material layer having a contact pad therein;
forming a dielectric layer on the material layer and the contact pad;
forming a doped oxide layer on the dielectric layer;
forming an oxide layer on the doped oxide layer;
performing a first etching process to remove part of the oxide layer, part of the doped oxide layer, and part of the dielectric layer to form a first contact hole;
performing a second etching process to remove part of the doped oxide layer to form a second contact hole after removing part of the dielectric layer and exposing the contact pad; and
forming a conductive layer in the second contact hole to form a contact plug.
2. The method of claim 1 , wherein the dielectric layer comprises silicon nitride.
3. The method of claim 1 , wherein the doped oxide layer comprises borosilicate phosphosilicate glass (BPSG) or phosphosilicate glass (PSG).
4. The method of claim 1 , wherein the oxide layer comprises tetraethyl orthosilicate (TEOS).
5. The method of claim 1 , wherein the second etching process uses a gas selected from the group consisting of ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ).
6. The method of claim 1 , wherein an etching selectivity of the doped oxide layer to the oxide layer is 200:1.
7. The method of claim 1 , further comprising a first step portion between the doped oxide layer and the dielectric layer.
8. The method of claim 1 , further comprising a second step portion between the doped oxide layer and the oxide layer.
9. The method of claim 1 , wherein the contact plug comprises tungsten.
10. The method of claim 1 , wherein the contact plug comprises a first portion in the dielectric layer, a second portion in the doped oxide layer, and a third portion in the oxide layer.
11. The method of claim 10 , wherein the first portion comprises a first inclined sidewall, the second portion comprises a vertical sidewall, and the third portion comprises a second inclined sidewall.
12. The method of claim 10 , further comprising an air gap in the second portion.
13. A semiconductor device, comprising:
a contact pad in a material layer;
a dielectric layer on the material layer and the contact pad;
a doped oxide layer on the dielectric layer;
an oxide layer on the doped oxide layer; and
a contact plug comprising a first portion in the dielectric layer, a second portion in the doped oxide layer, and a third portion in the oxide layer, wherein the second portion comprises an air gap in the doped oxide layer and a top surface of the air gap is lower than a top surface of the doped oxide layer.
14. The semiconductor device of claim 13 , wherein the dielectric layer comprises silicon nitride.
15. The semiconductor device of claim 13 , wherein the doped oxide layer comprises borosilicate phosphosilicate glass (BPSG) or phosphosilicate glass (PSG).
16. The semiconductor device of claim 13 , wherein the oxide layer comprises tetraethyl orthosilicate (TEOS).
17. The semiconductor device of claim 13 , further comprising a first step portion between the doped oxide layer and the dielectric layer.
18. The semiconductor device of claim 13 , further comprising a second step portion between the doped oxide layer and the oxide layer.
19. The semiconductor device of claim 13 , wherein the first portion comprises a first inclined sidewall, the second portion comprises a vertical sidewall, and the third portion comprises a second inclined sidewall.