Metal-insensitive epitaxy formation

1. A method of forming a field effect transistor (FET), the method comprising:

performing an etching process to a semiconductor substrate, thereby forming recesses in source and drain (S/D) regions of the semiconductor substrate;

forming, by a non-selective deposition process, a passivation material layer of a first semiconductor material in the recesses; and

epitaxially growing a second semiconductor material on the passivation material layer, thereby forming S/D features in the recesses, wherein the S/D features are separated from the semiconductor substrate by the passivation material layer, wherein the first semiconductor material is different than the second semiconductor material, wherein the epitaxially growing of the second semiconductor material includes performing a cyclic deposition and etching (CDE) process having a first deposition step and a second deposition step, and wherein the first deposition step and the second deposition step are performed at different temperatures.

2. The method of claim 1 , wherein the forming of the passivation material layer includes performing the non-selective deposition process using a precursor free of chlorine.

3. The method of claim 2 , wherein the forming of the passivation material layer includes epitaxially growing the passivation material layer of the first semiconductor material.

4. The method of claim 3 , wherein the first semiconductor material includes silicon carbide and the second semiconductor material includes silicon germanium.

5. The method of claim 3 , wherein the forming of the passivation material layer includes epitaxially growing the passivation material layer of the first semiconductor material that is free of dopant, using the precursor free of dopant-containing gas.

6. The method of claim 3 , wherein the forming of the passivation material layer includes forming a silicon carbide layer having a carbon atomic percentage ranging from 1.8% to 3%.

7. The method of claim 1 , wherein the forming of the passivation material layer includes forming the passivation material layer with a thickness ranging from 1 nm to 4 nm, effectively preventing interaction between chlorine and metal residuals under the passivation material layer.

8. The method of claim 1 , further comprising performing a fluorine treatment to the passivation material layer before the epitaxially growing of the second semiconductor material.

9. The method of claim 8 , wherein the performing of the fluorine treatment includes performing the fluorine treatment with a fluorine dose ranging from 1×10 14 ions/cm 2 to 2×10 15 ions/cm 2 .

10. The method of claim 1 , wherein the epitaxially growing of the second semiconductor material includes epitaxially growing the second semiconductor material with in-situ doping one of a n-type dopant and a p-type dopant.

11. The method of claim 1 , wherein

the CDE process includes a first cycle for deposition and a second cycle for etching; and

the second cycle uses a chlorine-containing gas that includes at least one of HCl and Cl 2 .

12. The method of claim 11 , wherein the first cycle of the CDE process uses a precursor that includes PH 3 , monomethylsilane (MMS), and at least one of SiH 4 and Si 2 H 6 .

13. The method of claim 11 , wherein the first cycle of the CDE process uses a precursor that includes B 2 H 6 , GeH 4 , and at least one of SiH 4 and Si 2 H 6 .

14. The method of claim 1 , wherein the passivation material layer is formed by the non-selective deposition process using a precursor that includes monomethylsilane (MMS) and at least one of silane (SiH 4 ) and disilane (SiH 6 ).

15. The method of claim 1 , further comprising:

prior to epitaxially growing the second semiconductor material, doping the passivation layer with fluorine atoms to form a fluorine-doped passivation layer; and

epitaxially growing a second semiconductor material on the fluorine-doped passivation material layer.

16. A method of forming a field effect transistor (FET), the method comprising:

performing an etching process to a semiconductor substrate, thereby forming recesses in source and drain (S/D) regions of the semiconductor substrate; and

epitaxially growing a semiconductor material by a deposition process with a varying etching/deposition (E/D) factor, thereby forming S/D features in the recesses, wherein the deposition process includes a co-flow epitaxy growth, wherein the deposition process includes a first deposition step performed at a first substrate temperature and a second deposition step performed after the first deposition step, and wherein the second deposition step is performed at a second substrate temperature different than the first substrate temperature.

17. The method of claim 16 , wherein the first deposition step has a first etch/deposition (E/D) factor and the second deposition step has a second E/D factor greater than the first E/D factor.

18. The method of claim 16 , wherein

the first deposition step is a non-selective deposition; and

the second deposition step is a selective deposition.

19. The method of claim 16 , wherein

the first substrate temperature is less than 620° C.; and

the second substrate temperature is greater than 620° C.

20. The method of claim 16 , wherein the deposition process includes a combination of the co-flow epitaxy growth and a cyclic deposition and etching (CDE) process.

21. The method of claim 16 , wherein the epitaxially growing of the semiconductor material includes varying the E/D factor by a mechanism selected from gas partial pressure, gas flow rate, substrate temperature, and a combination thereof.

22. The method of claim 16 , wherein the varying E/D factor includes a step-wise varying E/D factor.

23. A method of forming a field effect transistor (FET), the method comprising:

performing an etching process to a semiconductor substrate, thereby forming recesses in source and drain (S/D) regions of the semiconductor substrate;

forming, by a non-selective deposition process, a passivation layer of a first semiconductor material in the recesses;

after forming the passivation layer of the first semiconductor material, doping the passivation layer with fluorine atoms to form a fluorine-doped passivation layer; and

epitaxially growing a second semiconductor material over the fluorine-doped passivation layer, thereby forming S/D features in the recesses, wherein the first semiconductor material is different than the second semiconductor material, and wherein the epitaxially growing the second semiconductor material includes performing a cyclic deposition and etching (CDE) process having a first deposition step performed at a first temperature and a second deposition step performed at a second temperature different than the first temperature.

24. The method of claim 23 , wherein the doping is performed by a fluorine plasma treatment.

25. The method of claim 23 , wherein the fluorine-doped passivation layer has a fluorine concentration per unit area ranging from 1×10 14 cm −2 to 2×10 15 cm −2 .

26. The method of claim 23 , wherein the forming of the passivation layer includes performing the non-selective deposition process using a precursor free of chlorine; and the epitaxially growing of the second semiconductor material includes an etching process using a chlorine-containing gas.

27. The method of claim 23 , wherein the forming of the passivation layer includes epitaxially growing the first semiconductor material that is free of dopant, using a precursor free of dopant-containing gas.

28. The method of claim 27 , wherein the epitaxially growing of the second semiconductor material includes in-situ doping one of a n-type dopant and a p-type dopant to the second semiconductor material.

29. The method of claim 23 , wherein the passivation layer is formed by the non-selective deposition process using a precursor that includes monomethylsilane (MMS) and at least one of silane (SiH 4 ) and disilane (SiH 6 ).