Fin field-effect transistor device and method of forming the same
A method of forming a semiconductor device includes forming source/drain regions on opposing sides of a gate structure, where the gate structure is over a fin and surrounded by a first dielectric layer; forming openings in the first dielectric layer to expose the source/drain regions; selectively forming silicide regions in the openings on the source/drain regions using a plasma-enhanced chemical vapor deposition (PECVD) process; and filling the openings with an electrically conductive material.
1. A method of forming a semiconductor device, the method comprising:
forming source/drain regions on opposing sides of a gate structure, wherein the gate structure is over a fin and surrounded by a first dielectric layer;
forming openings in the first dielectric layer to expose the source/drain regions;
selectively forming silicide regions in the openings on the source/drain regions by performing a plasma-enhanced chemical vapor deposition (PECVD) process, wherein the PECVD process uses an RF source for generating plasmas, wherein performing the PECVD process comprises tuning an average energy of the plasmas in the PECVD process to be above a first activation energy for forming the silicide regions on the source/drain regions and below a second activation energy for forming the silicide regions on the first dielectric layer, wherein the PECVD process forms the silicide regions at bottoms of the openings on the source/drain regions but does not form a material along sidewalls of the openings; and
filling the openings with an electrically conductive material.
2. The method of claim 1 , further comprising before filling the openings, forming a barrier layer in the openings, wherein the barrier layer lines sidewalls of the first dielectric layer exposed by the openings and lines top surfaces of the silicide regions.
3. The method of claim 2 , further comprising before forming the barrier layer, converting an upper portion of the silicide regions into a self-aligned barrier layer, wherein the barrier layer physically contacts the self-aligned barrier layer.
4. The method of claim 3 , wherein converting the upper portion of the silicide regions comprises converting the upper portion of the silicide regions into a nitride or an oxide of the silicide regions.
5. The method of claim 1 , wherein the RF source is turned on and off alternately during the PECVD process, wherein the RF source is turned on for a first duration and turned off for a second duration in each cycle of the PECVD process, wherein tuning the average energy of the plasmas comprises adjusting the first duration and the second duration.
6. The method of claim 1 , wherein the silicide regions comprise titanium silicide, and the PECVD process is performed using a gas source comprising hydrogen and titanium tetrachloride.
7. The method of claim 6 , wherein a ratio between a flow rate of hydrogen and a flow rate of titanium tetrachloride is smaller than about 2.
8. The method of claim 7 , wherein a power of the RF source is between about 100 W and about 500 W.
9. The method of claim 8 , wherein a frequency of the RF source is between about 1 KHz and about 10 KHz, and a pressure of the PECVD process is between about 1 torr and about 10 torr.
10. The method of claim 1 , wherein filling the openings is performed after selectively forming the silicide regions without an intervening etching process for cleaning the openings.
11. A method of forming a semiconductor device, the method comprising:
determine a first activation energy for forming a third material on a first material of a semiconductor structure;
determine a second activation energy for forming the third material on a second material of the semiconductor structure, the second activation energy being higher than the first activation energy; and
selectively depositing the third material on the first material by performing a plasma-enhanced chemical vapor deposition (PECVD) process, wherein an average energy of plasmas of the PECVD process is above the first activation energy and smaller than the second activation energy, wherein the PECVD process forms the third material on the first material but not on the second material.
12. The method of claim 11 , wherein the plasmas of the PECVD process are generated using an RF source, wherein the RF source is turned on and off alternately during the PECVD process.
13. The method of claim 12 , further comprising adjusting the average energy of the plasmas of the PECVD process by adjusting a first duration during which the RF source is turned on and adjusting a second duration during which the RF source is turned off.
14. The method of claim 11 , wherein the first activation energy corresponds to a first dissociation energy for breaking first bonds between first atoms of the first material, and the second activation energy corresponds to a second dissociation energy for breaking second bonds between second atoms of the second material.
15. A method of forming a semiconductor device, the method comprising:
forming a dummy gate structure over a fin, the dummy gate structure being surrounded by a first dielectric layer, the first dielectric layer covering source/drain regions disposed on opposing sides of the dummy gate structure;
replacing the dummy gate structure with a metal gate structure;
forming openings in the first dielectric layer to expose the source/drain regions;
selectively forming a silicide material at bottoms of the openings on the source/drain regions by performing a plasma-enhanced chemical vapor deposition (PECVD) process, wherein an RF source for the PECVD process is turned on and off periodically during the PECVD process, wherein the PECVD process covers the source/drain regions with the silicide material but exposes the first dielectric layer;
converting an upper portion of the silicide material into a self-aligned barrier layer by supplying a nitrogen-containing gas or a nitrogen-containing plasma to the silicide material, wherein sidewalls of the openings are free of the self-aligned barrier layer; and
filling the openings with a conductive material.
16. The method of claim 15 , further comprising adjusting an average energy of plasmas of the PECVD process by adjusting an ON-time and an OFF-time in a cycle of the PECVD process, wherein the ON-time is a first duration of the cycle of the PECVD process during which the RF source is turned on, and the OFF-time is a second duration of the cycle of the PECVD process during which the RF source is turned off.
17. The method of claim 16 , wherein the ON-time and the OFF-time are adjusted to tune the average energy of the plasmas to be above a first activation energy for forming the silicide material on the source/drain regions and below a second activation energy for forming the silicide material on the first dielectric layer.
18. The method of claim 15 , wherein the silicide material is titanium silicide, and the PECVD process is performed using a gas comprising hydrogen and titanium tetrachloride, wherein a ratio between a flow rate of hydrogen and a flow rate of titanium tetrachloride is smaller than about 2.
19. The method of claim 15 , wherein a width of the silicide material is wider than a width of the openings measured at the bottoms of the openings such that the silicide material extends directly under the first dielectric layer between the first dielectric layer and the source/drain regions.
20. The method of claim 15 , further comprising, after the converting and before filling the openings, forming a barrier layer in the openings, wherein the barrier layer extends along, and contacts, sidewalls of the first dielectric layer exposed by the openings and the self-aligned barrier layer.