Fin field-effect transistor device and method

1. A method of forming a semiconductor device, the method comprising:

forming a metal gate structure over a fin, the fin protruding above a substrate, the metal gate structure being surrounded by an interlayer dielectric (ILD) layer;

recessing the metal gate structure below an upper surface of the ILD layer distal from the substrate;

after the recessing, forming a first dielectric layer over the recessed metal gate structure;

forming an etch stop layer over the first dielectric layer and the ILD layer;

forming a second dielectric layer over the etch stop layer;

performing a first dry etch process to form a first opening that extends through the second dielectric layer, through the etch stop layer, and into the first dielectric layer;

after the first dry etch process, performing a wet etch process to clean the first opening; and

after the wet etch process, performing a second dry etch process to extend the first opening through the first dielectric layer.

2. The method of claim 1 , further comprising, after the second dry etch process, filling the first opening with a conductive material.

3. The method of claim 1 , wherein an upper surface of the first dielectric layer is formed to be level with the upper surface of the ILD layer.

4. The method of claim 1 , further comprising, before forming the first dielectric layer, recessing gate spacers of the metal gate structure below the upper surface of the ILD layer, wherein the first dielectric layer is formed over the recessed gate spacers.

5. The method of claim 1 , wherein the first dry etch process is a first plasma process, and the second dry etch process is a second plasma process.

6. The method of claim 5 , wherein the first plasma process is performed with a first bias power, and the second plasma process is performed with a second bias power different from the first bias power.

7. The method of claim 6 , wherein the second bias power is lower than the first bias power.

8. The method of claim 1 , wherein the first dielectric layer is formed of silicon nitride, and the second dielectric layer is formed of silicon oxide.

9. The method of claim 8 , wherein the first dry etch process is a first plasma process performed using a first process gas comprising C 4 F 6 , C 4 F 8 , or CH 2 F 2 , and the second dry etch process is a second plasma process performed using a second process gas comprising CH 2 F 2 and H 2 .

10. The method of claim 9 , wherein the wet etch process is performed using a wet clean chemical comprising HCl and H 2 CO 3 .

11. The method of claim 1 , further comprising, after forming the first dielectric layer and before forming the etch stop layer:

removing a portion of the ILD layer adjacent to the metal gate structure to form a second opening in the ILD layer, the second opening exposing an underlying source/drain region;

filling the second opening with a conductive material; and

after the filling, performing a planarization process to remove portions of the conductive material disposed outside the second opening.

12. The method of claim 11 , wherein after the planarization process, a residue portion of the conductive material remains on an upper surface of the first dielectric layer, wherein the method further comprises:

forming a third opening that extends through the second dielectric layer and the etch stop layer using the first dry etch process, wherein a bottom of the third opening exposes the residue portion of the conductive material;

etching through the residue portion of the conductive material to expose the first dielectric layer using the wet etch process; and

extending the third opening through the first dielectric layer using the second dry etch process.

13. A method of forming a semiconductor device, the method comprising:

recessing a gate structure below an upper surface of a dielectric layer, the dielectric layer surrounding the gate structure;

forming a first dielectric material over the recessed gate structure;

forming a second dielectric material over the first dielectric material;

forming an opening that extends through the second dielectric material and into the first dielectric material using a first dry etch process;

after the first dry etch process, wet cleaning the opening;

after the wet cleaning, extending the opening through the first dielectric material using a second dry etch process; and

filling the opening with a conductive material.

14. The method of claim 13 , wherein the first dry etch process is a first plasma process, and the second dry etch process is a second plasma process.

15. The method of claim 14 , wherein a first bias power of the first plasma process is higher than a second bias power of the second plasma process.

16. The method of claim 14 , wherein the first dielectric material is a nitride, and the second dielectric material is an oxide.

17. The method of claim 16 , wherein the first plasma process is performed using a first process gas comprising C 4 F 6 , C 4 F 8 , or CH 2 F 2 , the second plasma process is performed using a second process gas comprising CH 2 F 2 and H 2 , and the wet cleaning is performed using a wet clean chemical comprising HCl and H 2 CO 3 .

18. A method of forming a semiconductor device, the method comprising:

forming a gate structure over a fin that protrudes above a substrate, wherein the gate structure is surrounded by a dielectric layer;

forming a nitride layer over the gate structure;

forming an etch stop layer over the nitride layer;

forming an oxide layer over the etch stop layer;

forming a first opening that extends through the oxide layer, through the etch stop layer, and into the nitride layer by a first dry etch process;

cleaning the first opening by a wet etch process after the first dry etch process;

after cleaning the first opening, extending the first opening through the nitride layer by a second dry etch process; and

filling the first opening with a conductive material after the second dry etch process.

19. The method of claim 18 , wherein the first dry etch process is a first plasma etch process performed with a first bias power, and the second dry etch process is a second plasma etch process performed with a second bias power lower than the first bias power.

20. The method of claim 18 , further comprising:

forming a second opening that extends through the oxide layer and through the etch stop layer by the first dry etch process, wherein a bottom of the second opening exposes a metal area disposed between the etch stop layer and the nitride layer;

etching through the metal area by the wet etch process; and

extending the second opening through the nitride layer by the second dry etch process.