Method to induce strain in finFET channels from an adjacent region
Methods and structures for forming strained-channel finFETs are described. Fin structures for finFETs may be formed using two epitaxial layers of different lattice constants that are grown over a bulk substrate. A first thin, strained, epitaxial layer may be cut to form strain-relieved base structures for fins. The base structures may be constrained in a strained-relieved state. Fin structures may be epitaxially grown in a second layer over the base structures. The constrained base structures can cause higher amounts of strain to form in the epitaxially-grown fins than would occur for non-constrained base structures.
1. A finFET comprising:
a substrate;
a strain-inducing base structure vertically above the substrate, the strain-inducing base structure comprising a first semiconductor material having a first lattice constant;
a constraining material laterally adjacent the strain-inducing base structure, the constraining material having a Young's modulus higher than a Young's modulus of the strain inducing base structure; and
a fin vertically above the strain-inducing base structure and comprising a second semiconductor material having a second lattice constant that is different than the first lattice constant.
2. The finFET structure of claim 1 , wherein the first semiconductor material comprises SiGe or SiC.
3. The finFET structure of claim 2 , wherein a Ge or C content of the SiGe or SiC is between approximately 10% and approximately 25%.
4. The finFET structure of claim 2 , wherein a Ge or C content of the SiGe or SiC is between approximately 25% and approximately 40%.
5. The finFET structure of claim 2 , wherein the first semiconductor material has a gradient in Ge or C concentration in a direction perpendicular to an interfacial surface between the strain-inducing feature and the fin.
6. The finFET structure of claim 1 , wherein the second semiconductor material comprises Si.
7. The finFET structure of claim 1 , wherein a thickness of the first semiconductor material is between approximately 10 nm and approximately 60 nm.
8. The finFET structure of claim 1 , wherein a thickness of the second semiconductor material is between approximately 10 nm and approximately 60 nm.
9. The finFET structure of claim 1 , wherein the fin has a width between approximately 5 nm and approximately 30 nm.
10. The finFET structure of claim 9 , further comprising a gate structure formed at a center region of the fin.
11. The finFET structure of claim 10 disposed in a smart phone, computer, tablet computer, PDA, or video display.
12. The finFET structure of claim 1 , wherein the Young's modulus of the constraining material is at least twice the value of the Young's modulus of the strain-inducing base structure.