Fin field-effect transistor device and method
A method includes forming a doped region on a top portion of a substrate, forming a first epitaxial layer over the substrate, forming a recess in the first epitaxial layer, the recess being aligned to the doped region, performing a surface clean treatment in the recess, the surface clean treatment includes: oxidizing surfaces of the recess to form an oxide layer in the recess, and removing the oxide layer from the surfaces of the recess, and forming a second epitaxial layer in the recess.
1. A method of forming a semiconductor device, the method comprising:
forming a doped region on a top portion of a substrate;
forming a first epitaxial layer over the substrate;
forming a recess in the first epitaxial layer, the recess being aligned to the doped region;
performing a surface clean treatment in the recess, the surface clean treatment comprises:
performing a plasma ashing process in the recess, wherein the plasma ashing process comprises exposing surfaces of the recess to a plasma that includes chlorine gas;
oxidizing the surfaces of the recess to form an oxide layer in the recess; and
removing the oxide layer from the surfaces of the recess; and
forming a second epitaxial layer in the recess.
2. The method of claim 1 , wherein forming the recess comprises etching the first epitaxial layer.
3. The method of claim 1 , wherein performing the surface clean treatment further comprises
removing contaminants from the surfaces of the recess.
4. The method of claim 1 , wherein exposing surfaces of the recess to the plasma reduces a surface roughness of the surfaces of the recess.
5. The method of claim 3 , wherein removing contaminants from the surfaces of the recess comprises a wet process that exposes the surfaces of the recess to sulfuric acid (H 2 SO 4 ), hydrogen peroxide (H 2 O 2 ), ammonium hydroxide (NH 4 OH), or combinations thereof.
6. The method of claim 1 , wherein oxidizing the surfaces of the recess comprises exposing the surfaces of the recess to a process gas comprising ozone (O 3 ).
7. The method of claim 1 , wherein removing the oxide layer comprises a wet etching process using dilute hydrofluoric acid (dHF).
8. The method of claim 1 , wherein the first epitaxial layer comprises a first material and the second epitaxial layer comprises a second material, wherein the first material has a different lattice constant than the second material.
9. A method of forming a semiconductor device, the method comprising:
forming a first doped region and a second doped region in a top portion of a substrate;
growing a first epitaxial layer over the first doped region and the second doped region;
etching the first epitaxial layer to form a recess, wherein the recess is aligned to the first doped region;
performing a surface clean treatment in the recess, the surface clean treatment comprises:
smoothening surfaces of the recess, wherein smoothening surfaces of the recess comprises performing a plasma ashing process on the surfaces of the recess, and wherein the plasma ashing process uses chlorine plasma;
removing particles from the surfaces of the recess using a wet clean process; and
removing portions of the first epitaxial layer from the recess, wherein removing the portions of the first epitaxial layer from the recess comprises:
forming an oxide layer in the portions of the first epitaxial layer in the recess; and
etching the oxide layer;
depositing a seed layer in the recess; and
growing a second epitaxial layer in the recess and over the seed layer.
10. The method of claim 9 , wherein the first doped region and the second doped region are oppositely doped.
11. The method of claim 9 , further comprising:
forming a first fin, wherein the first fin comprises a first portion of the first doped region, a second portion of the first epitaxial layer, and a third portion of the second epitaxial layer; and
forming a second fin, wherein the second fin comprises a fourth portion of the second doped region and a fifth portion of the first epitaxial layer.
12. The method of claim 9 , wherein forming the seed layer comprises a deposition temperature in a range of 600° C. to 750° C.
13. The method of claim 9 , wherein growing the second epitaxial layer comprises a growth temperature in a range of 550° C. to 700° C.
14. The method of claim 9 , wherein a deposition temperature of the seed layer is higher than a growth temperature of the second epitaxial layer.
15. The method of claim 9 , wherein the plasma ashing process is performed at a temperature that is in a range from 20° C. to 90° C.
16. The method of claim 9 , wherein etching the oxide layer comprises an etching process that includes dilute hydrofluoric (dHF) acid.
17. A method of forming a semiconductor device, the method comprising:
etching a first semiconductor layer to form a recess, wherein the etching damages portions of the first semiconductor layer, the recess exposes the damaged portions of the first semiconductor layer;
performing a surface clean treatment in the recess, the surface clean treatment comprises:
exposing surfaces of the recess to a plasma, wherein the plasma comprises chlorine gas;
forming an oxide layer in the damaged portions of the first semiconductor layer; and
removing the oxide layer;
forming a seed layer in the recess; and
forming a second semiconductor layer in the recess.
18. The method of claim 17 further comprising:
forming an n-type doped region in a substrate; and
depositing the first semiconductor layer over the n-type doped region.
19. The method of claim 17 , wherein the seed layer comprises silicon, carbon doped silicon, silicon germanium, or a combination thereof.
20. The method of claim 17 , wherein forming an oxide layer comprises a dry process that exposes the surfaces of the recess to a process gas that comprises ozone ( 03 ), and removing the oxide layer comprises a wet process that etches the oxide layer using dilute hydrofluoric acid (dHF).