Patent ID: 9425293
Filing Date: 2016-08-23
CPC Classification: B82Y,H01L

Claim Text:
1. A method of forming a semiconductor structure, said method comprising: providing a fin structure comprising, from bottom to top, a silicon portion and a multilayered stack of heterostructure portions, each heterostructure portion including, from bottom to top, a silicon germanium alloy portion having a first germanium content and a silicon portion, wherein each silicon germanium alloy portion of each heterostructure portion has a different thickness that increases from the bottommost heterostructure portion to the topmost heterostructure portion; suspending a middle segment of each silicon germanium alloy portion of each heterostructure portion; forming an oxygen impermeable structure atop the silicon germanium alloy portion of the topmost heterostructure portion and within a gap located beneath each silicon germanium alloy portion; recessing the oxygen impermeable structure below the silicon germanium alloy portion of the topmost heterostructure portion, while maintaining said oxygen impermeable structure on remaining silicon germanium alloy portions; oxidizing said silicon germanium alloy portion of the topmost heterostructure portion to provide a topmost silicon germanium alloy nanowire having a reduced thickness and a second germanium content that is greater than the first germanium content; removing surface oxide formed on said topmost silicon germanium alloy nanowire having said second germanium content; and repeating, any number of times, said steps of recessing said oxygen impermeable structure, said oxidizing, and said removing said surface on each remaining silicon germanium alloy portion of each heterostructure portion that is located above a bottommost silicon germanium alloy layer of the bottommost heterostructure portion to provide a nanowire stack containing silicon germanium alloy nanowires, wherein the germanium content of each silicon germanium alloy nanowire of said nanowire stack increases from bottom to top.