Selective NFET/PFET recess of source/drain regions
A method includes forming an inter-layer dielectric over a first source/drain region and a second source/drain region. The first source/drain region and the second source/drain region are of n-type and p-type, respectively. The inter-layer dielectric is etched to form a first contact opening and a second contact opening, with the first source/drain region and the second source/drain region exposed to the first contact opening and the second contact opening, respectively. A process gas is used to etch back the first source/drain region and the second source/drain region simultaneously, and a first etching rate of the first source/drain region is higher than a second etching rate of the second source/drain region. A first silicide region and a second silicide region are formed on the first source/drain region and the second source/drain region, respectively.
1. A method comprising:
forming an inter-layer dielectric over a first source/drain region and a second source/drain region, wherein the first source/drain region and the second source/drain region are of n-type and p-type, respectively; then
adjusting a temperature of a wafer comprising the first source/drain region to lower than 20° C.:
after the adjusting the temperature of the wafer, etching the inter-layer dielectric to form a first contact opening and a second contact opening, with the first source/drain region and the second source/drain region exposed to the first contact opening and the second contact opening, respectively;
conducting a process gas to etch back the first source/drain region and the second source/drain region simultaneously, wherein a first etching rate of the first source/drain region is higher than a second etching rate of the second source/drain region; and
forming a first silicide region and a second silicide region on the first source/drain region and the second source/drain region, respectively.
2. The method of claim 1 , wherein the process gas comprises:
a sulfur-containing gas; and
a carbon-and-fluorine containing gas.
3. The method of claim 2 , wherein the process gas further comprises HBr or CL.
4. The method of claim 1 further comprising, before the conducting the process gas, adjusting a temperature of a wafer that comprises the first source/drain region and the second source/drain region to lower than 20° C.
5. The method of claim 1 , wherein a ratio of the first etching rate to the second etching rate is higher than about 1.5.
6. The method of claim 1 , wherein in the etching, a first polymer layer comprising carbon and fluorine is formed on the first source/drain region, and a second polymer layer comprising carbon, fluorine, germanium, and sulfur is formed on the second source/drain region.
7. The method of claim 6 , wherein in the etching, a ratio of a first thickness of the first polymer layer to a second thickness of the second polymer layer is greater than about 2.0.
8. The method of claim 6 further comprising removing the first polymer layer and the second polymer layer before the first silicide region and the second silicide region are formed.
9. A method comprising:
performing a first epitaxy to form a first source/drain region for an n-type Fin Field-Effect transistor (FinFET);
adjusting a temperature of a wafer comprising the first source/drain region to lower than 20° C.:
after the adjusting the temperature, etching-back the first source/drain region using a process gas, wherein the etching-back is performed at the temperature lower than 20° C., wherein the process gas comprises carbon oxide sulfide and a carbon-and-fluorine containing gas, wherein the etching-back generates a recess extending from a top surface of the first source/drain region into the first source/drain region; and
forming a first silicide region on the first source/drain region, wherein the first silicide region comprises a bottom portion and sidewall portions over and connected to opposite ends of the bottom portion.
10. The method of claim 9 , wherein the process gas further comprises an etching gas configured to etch back the first source/drain region.
11. The method of claim 9 further comprising:
performing a second epitaxy to form a second source/drain region for a p-type FinFET, wherein in the etching-back, the second source/drain region is exposed to the process gas.
12. A method comprising:
forming an inter-layer dielectric over a first source/drain region and a second source/drain region, wherein the first source/drain region and the second source/drain region are of n-type and p-type, respectively;
etching the inter-layer dielectric to form a first contact opening and a second contact opening, with the first source/drain region and the second source/drain region exposed to the first contact opening and the second contact opening, respectively, wherein in the etching, a first polymer layer comprising carbon and fluorine is formed on the first source/drain region, and a second polymer layer comprising carbon, fluorine, germanium, and sulfur is formed on the second source/drain region;
conducting a process gas to etch back the first source/drain region and the second source/drain region simultaneously, wherein a first etching rate of the first source/drain region is higher than a second etching rate of the second source/drain region; and
forming a first silicide region and a second silicide region on the first source/drain region and the second source/drain region, respectively.
13. The method of claim 12 , wherein the process gas comprises:
a sulfur-containing gas; and
a carbon-and-fluorine containing gas.
14. The method of claim 13 , wherein the process gas further comprises HBr or CL.
15. The method of claim 12 further comprising, before the conducting the process gas, adjusting a temperature of a wafer that comprises the first source/drain region and the second source/drain region to lower than 20° C.
16. The method of claim 12 , wherein the first source/drain region comprises silicon and is free from germanium, and the second source/drain region comprises silicon germanium.
17. The method of claim 12 , wherein a ratio of the first etching rate to the second etching rate is higher than about 1.5.
18. The method of claim 12 , wherein in the etching, a ratio of a first thickness of the first polymer layer to a second thickness of the second polymer layer is greater than about 2.0.
19. The method of claim 12 further comprising removing the first polymer layer and the second polymer layer before the first silicide region and the second silicide region are formed.
20. The method of claim 19 , wherein the removing the first polymer layer and the second polymer layer is performed using a mixed gas comprising N 2 and H 2 , or using a wet solution comprising ozone (O 3 ).