High percentage silicon germanium alloy fin formation
A layer of a silicon germanium alloy containing 30 atomic percent or greater germanium and containing substitutional carbon is grown on a surface of a semiconductor layer. The presence of the substitutional carbon in the layer of silicon germanium alloy compensates the strain of the silicon germanium alloy, and suppresses defect formation. Placeholder semiconductor fins are then formed to a desired dimension within the layer of silicon germanium alloy and the semiconductor layer. The placeholder semiconductor fins will relax for the most part, while maintaining strain in a lengthwise direction. An anneal is then performed which may either remove the substitutional carbon from each placeholder semiconductor fin or move the substitutional carbon into interstitial sites within the lattice of the silicon germanium alloy. Free-standing permanent semiconductor fins containing 30 atomic percent or greater germanium, and strain in the lengthwise direction are provided.
1. A method of forming a semiconductor structure comprising:
forming at least one placeholder semiconductor fin on a surface of a substrate, wherein said at least one placeholder semiconductor fin comprises, from bottom to top, a semiconductor material portion and a silicon germanium alloy portion, said silicon germanium alloy portion contains 30 atomic percent or greater germanium, a first content of substitutional carbon and a strain in a lengthwise direction of said at least one placeholder semiconductor fin; and
annealing said at least one placeholder semiconductor fin, wherein said annealing converts said at least one placeholder semiconductor fin into at least one permanent semiconductor fin comprises, for bottom to top, said semiconductor material portion and a silicon germanium alloy portion, said silicon germanium alloy portion of said at least one permanent semiconductor fin contains 30 atomic percent or greater germanium, a second content of substitutional carbon and a strain in a lengthwise direction of said at least one permanent semiconductor fin, wherein said second content of substitutional carbon is less than said first content of substitutional carbon.
2. The method of claim 1 , wherein said forming the at least one placeholder semiconductor fin comprises:
epitaxially growing a layer of silicon germanium alloy containing 30 atomic percent or greater germanium and said first content of substitutional carbon on a semiconductor material of said substrate;
forming a patterned photoresist on a surface of said layer of silicon germanium alloy; and
etching exposed portions of said layer of silicon germanium alloy and underlying portions of said semiconductor material of said substrate utilizing said patterned photoresist as an etch mask.
3. The method of claim 2 , wherein said layer of silicon germanium alloy is strained, and after forming said at least one placeholder semiconductor fin, said silicon germanium alloy portion contains a strain only in a lengthwise direction.
4. The method of claim 1 , wherein said annealing at least partially removes some of said substitutional carbon as carbon dioxide.
5. The method of claim 1 , wherein said annealing at least partially moves some of said substitutional carbon into an interstitial lattice sites.
6. The method of claim 1 , wherein said annealing is performed at a temperature from 900° C. to 1250° C. in the absence of oxygen.
7. The method of claim 6 , wherein said annealing is performed at a temperature from 900° C. to 1250° C. in presence of an inert gas admixed with from 0.1% to 10% oxygen.
8. The method of claim 1 , wherein said annealing is performed during a process of forming an isolation structure on exposed surfaces of said substrate.
9. The method of claim 1 , wherein said at least one permanent semiconductor fin further includes a hard mask cap portion located on an upper surface of said silicon germanium alloy portion.
10. The method of claim 1 , further comprising forming a gate structure straddling said at least one permanent semiconductor fin, wherein said forming said gate structure comprises:
depositing a gate dielectric portion on at least vertical sidewalls of said at least one permanent semiconductor fin; and
forming a gate conductor portion on said gate dielectric portion and atop an upper surface of said at least one permanent semiconductor fin.