Surface roughness of III-V fin formed on silicon sidewall by implementing sacrificial buffers
A method for use in forming a fin of a field-effect transistor includes: patterning a mandrel into a substrate at least by recessing portions of the substrate; forming dielectric material at least on the recessed portions of the substrate, wherein the dielectric material partially covers exterior sidewalls of the mandrel; forming a first buffer at least on a portion of the exterior sidewalls of the mandrel not covered by the dielectric material; forming a second buffer at least on exterior sidewalls of the first buffer; forming a semiconductor channel at least on the dielectric material, wherein at least the second buffer is between the channel and the mandrel; exposing interior sidewalls of at least the first buffer at least by removing the mandrel; and removing the first buffer and the second buffer without removing the channel.
1. A method for use in forming a fin of a field-effect transistor, the method comprising the steps of:
patterning a mandrel into a substrate at least by recessing portions of the substrate;
forming dielectric material at least on the recessed portions of the substrate, wherein the dielectric material partially covers exterior sidewalls of the mandrel;
forming a first buffer at least on a portion of the exterior sidewalls of the mandrel not covered by the dielectric material;
forming a second buffer at least on exterior sidewalls of the first buffer;
forming a semiconductor channel at least on the dielectric material, wherein at least the second buffer is between the channel and the mandrel;
exposing interior sidewalls of at least the first buffer at least by removing the mandrel; and
removing the first buffer and the second buffer without removing the channel.
2. The method of claim 1 , wherein at least the recessed portions of the substrate comprise (110) silicon, and wherein at least the exterior sidewalls of the mandrel comprise (111) silicon.
3. The method of claim 1 , wherein the first buffer comprises a wetting layer, and wherein the second buffer comprises an interlayer.
4. The method of claim 1 , wherein the second buffer creates a single crystalline growth-front facet.
5. The method of claim 1 , wherein patterning the mandrel comprises:
forming a hard mask covering a portion of the substrate; and
recessing portions of the substrate not covered by the hard mask;
wherein the mandrel comprises the portions of the substrate covered by the hard mask; and
wherein the hard mask is removed before the mandrel is removed.
6. The method of claim 5 , wherein the second buffer is formed at least in part on exterior sidewalls of the hard mask.
7. The method of claim 6 wherein the first buffer is not formed on the exterior sidewalls of the hard mask.
8. The method of claim 5 , wherein forming the dielectric material comprises:
covering the exterior sidewalls of the mandrel by filling the recessed portions of the substrate with the dielectric material;
polishing the dielectric material to the hard mask; and
exposing the portion of the exterior sidewalls of the mandrel by recessing the first dielectric.
9. The method of claim 8 , wherein the hard mask comprises a nitride, and wherein the dielectric material comprises an oxide.
10. The method of claim 8 , further comprising:
forming an etch stop on exterior sidewalls of the channel and on at least part of the dielectric material;
forming additional dielectric material on the etch stop;
polishing the additional dielectric material to the hard mask; and
removing the additional dielectric material;
wherein the etch stop protects the channel at least when the additional dielectric material is removed; and
wherein the etch stop is removed after the additional dielectric material is removed.
11. The method of claim 10 , wherein the additional dielectric material is removed when the mandrel is removed.
12. The method of claim 10 , wherein the additional dielectric material is removed after the first and second buffers are removed.
13. The method of claim 10 , wherein the etch stop protects the channel when removing at least the second buffer, and wherein the etch stop is removed after removing at least the second buffer.
14. The method of claim 1 , wherein the exterior sidewalls of the mandrel cover interior sidewalls of the dielectric material.
15. The method of claim 14 , wherein after the mandrel is removed, at least a first portion of the interior sidewalls of the dielectric material is covered by the substrate, and at least a second portion of the interior sidewalls of the dielectric material is exposed.
16. The method of claim 1 , wherein the channel is formed at least in part on exterior sidewalls of the second buffer.
17. The method of claim 1 , wherein:
a third buffer is formed at least in part on exterior sidewalls of the second buffer;
the channel is formed at least in part on exterior sidewalls of the third buffer;
the third buffer protects the channel at least when removing the second buffer; and
the third buffer is removed after removing the second buffer.
18. The method of claim 17 , wherein:
an etch stop is formed at least in part on exterior sidewalls of the channel;
the etch stop protects the channel at least when removing the third buffer; and
the etch stop is removed after removing the third buffer.
19. The method of claim 17 , wherein the third buffer comprises a semiconductor, and wherein the etch stop comprises a dielectric.
20. The method of claim 1 , wherein exterior sidewalls of the second buffer are at a substantially uniform distance from the mandrel.