Method for manufacturing semiconductor structure with multi spacers
A semiconductor structure and a method for forming the same are provided. The semiconductor structure includes a fin structure formed over a substrate and a gate structure formed across the fin structure. The semiconductor structure further includes a bottom spacer formed on a lower part of a sidewall of the gate structure and an upper spacer formed on an upper part of the sidewall of the gate structure. In addition, the upper spacer includes an air gap formed in a dielectric material.
1. A method for manufacturing a semiconductor structure, comprising:
forming a fin structure over a substrate;
forming a gate structure across the fin structure;
forming a bottom spacer over a lower part of a sidewall of the gate structure;
forming a dummy spacer layer over an upper part of the sidewall of the gate structure;
removing at least a portion of the dummy spacer layer to form a gap exposing the upper part of the sidewall of the gate structure; and
forming an upper spacer in the gap.
2. The method for manufacturing the semiconductor structure as claimed in claim 1 , wherein the upper spacer comprises an air gap formed in a dielectric material.
3. The method for manufacturing the semiconductor structure as claimed in claim 1 , wherein the bottom spacer and the dummy spacer layer are made of different materials.
4. The method for manufacturing the semiconductor structure as claimed in claim 1 , further comprising:
forming a bottom interlayer dielectric layer over the substrate before the dummy spacer layer is formed,
wherein the dummy spacer layer further extends on a top surface of the bottom interlayer dielectric layer.
5. The method for manufacturing the semiconductor structure as claimed in claim 4 , wherein a top surface of the bottom interlayer dielectric layer is at a position that is lower than a top surface of the bottom spacer.
6. The method for manufacturing the semiconductor structure as claimed in claim 4 , further comprising:
forming an upper interlayer dielectric layer over the dummy spacer layer,
wherein the upper spacer is located between the upper interlayer dielectric layer and the gate structure.
7. The method for manufacturing a semiconductor structure as claimed in claim 4 , wherein the upper spacer does not completely fill in the gap formed by removing at least a portion of the dummy spacer layer, such that a second air gap is formed at an end of the dummy spacer layer extending on the top surface of the bottom interlayer dielectric layer.
8. A method for manufacturing a semiconductor structure, comprising:
forming a fin structure over a substrate;
forming an isolation structure around the fin structure;
forming a gate structure across the fin structure and over the isolation structure;
forming a bottom spacer over a lower part of a sidewall of the gate structure;
forming a dummy spacer layer having a first portion over an upper part of the sidewall of the gate structure and a second portion extending along a top surface of the isolation structure;
forming an interlayer dielectric layer covering the first portion and the second portion of the dummy spacer layer; and
replacing the first portion of the dummy spacer layer with an upper spacer.
9. The method for manufacturing a semiconductor structure as claimed in claim 8 , further comprising:
replacing the gate structure with a metal gate structure,
wherein the bottom spacer is located at a lower part of a sidewall of the metal gate structure, and the upper spacer is located at an upper part of the sidewall of the metal gate structure.
10. The method for manufacturing a semiconductor structure as claimed in claim 9 , wherein replacing the first portion of the dummy spacer layer with the upper spacer comprises:
removing the first portion of the dummy gate spacer to form a gap between the metal gate structure and the interlayer dielectric layer; and
forming the upper spacer in the gap.
11. The method for manufacturing the semiconductor structure as claimed in claim 8 , wherein the upper spacer comprises a first air gap formed in a dielectric material.
12. The method for manufacturing a semiconductor structure as claimed in claim 11 , wherein the second portion of the dummy spacer layer and the upper spacer are separated by a second air gap.
13. The method for manufacturing a semiconductor structure as claimed in claim 12 , wherein the second air gap exposes a portion of the upper spacer.
14. The method for manufacturing the semiconductor structure as claimed in claim 8 , wherein the bottom spacer and the dummy spacer layer are made of different materials.
15. A method for manufacturing a semiconductor structure, comprising:
forming a fin structure over a substrate;
forming an isolation structure around the fin structure;
forming a gate structure across the fin structure;
forming a bottom spacer over a lower part of a sidewall of the gate structure and a bottom interlayer dielectric layer around the bottom spacer;
forming a dummy spacer layer having a first portion over an upper part of the sidewall of the gate structure and a second portion over the bottom interlayer dielectric layer;
forming an upper interlayer dielectric layer over the second portion of the dummy spacer layer; and
replacing the first portion of the dummy spacer layer with an upper spacer.
16. The method for manufacturing a semiconductor structure as claimed in claim 15 , wherein the upper spacer comprises a first air gap formed in a dielectric material.
17. The method for manufacturing a semiconductor structure as claimed in claim 15 , wherein the upper spacer and the second portion of the dummy spacer layer are separated by a second air gap.
18. The method for manufacturing a semiconductor structure as claimed in claim 17 , wherein a bottommost portion of the second air gap is at a position higher than a bottom surface of the gate structure.
19. The method for manufacturing a semiconductor structure as claimed in claim 17 , wherein the second air gap exposes a portion of the upper spacer.
20. The method for manufacturing a semiconductor structure as claimed in claim 15 , wherein a top surface of the bottom interlayer dielectric layer is lower than a top surface of the bottom spacer.