Multi-layer strained channel FinFET
Methods and structures for forming a localized, strained region of a substrate are described. Trenches may be formed at boundaries of a localized region of a substrate. An upper portion of sidewalls at the localized region may be covered with a covering layer, and a lower portion of the sidewalls at the localized region may not be covered. A converting material may be formed in contact with the lower portion of the localized region, and the substrate heated. The heating may introduce a chemical species from the converting material into the lower portion, which creates stress in the localized region. The methods may be used to form strained-channel finFETs.
1. A finFET, comprising:
a substrate having a first surface, the substrate including a strain-inducing layer that forms the first surface; and
a fin formed on the first surface, the fin having a substantially consistent width, the fin including:
a channel region formed of a first semiconductor material having a first chemical composition; and
a strain-inducing portion that induces strain in the channel region, the strain-inducing portion including the first semiconductor material and a second semiconductor material having a second chemical composition that is different from the first chemical composition, the strain-inducing portion being between the channel region and the strain-inducing layer.
2. The finFET of claim 1 , wherein the second semiconductor material includes a chemical additive in addition to the first semiconductor material, and wherein a concentration of the chemical additive varies across the fin.
3. The finFET of claim 2 , wherein the concentration of the chemical additive is higher at edge regions of the fin than at a center of the fin.
4. The finFET of claim 2 , wherein the chemical additive includes one or more of germanium or carbon and the first semiconductor material is silicon.
5. The finFET of claim 1 , wherein the width of the fin is in the range of about 1-25 nm.
6. The finFET of claim 1 , further comprising a layer of covering material that covers the channel region of the fin but does not cover the strain-inducing portion of the fin.
7. The finFET of claim 6 wherein the covering material includes one or more of an oxide or a nitride.
8. The finFET of claim 1 , further comprising a gate structure formed adjacent to the channel region of the fin.
9. The finFET of claim 1 , further comprising a continuous layer of insulating material between the fin and the strain-inducing layer on the substrate.
10. The finFET of claim 1 wherein the strain-inducing portion has a defect density greater than 10 5 defects/cm 2 .
11. A device, comprising:
a substrate;
a fin formed on the substrate, the fin having a length extending parallel to a surface of the substrate and a height extending perpendicular to a surface of the substrate, the fin including:
a first portion including a channel;
a second portion between the first portion and the substrate, the second portion configured to strain the first portion;
a gate dielectric adjacent to the first portion;
a gate electrode adjacent to the gate dielectric; and
an insulating layer adjacent to the second portion, the insulating layer separating the gate dielectric and the gate electrode from the substrate, the insulating layer further separating the fin from the substrate.
12. The device of claim 11 , wherein the fin has a width between in the range of about 1-25 nm.
13. The device of claim 11 , wherein the first semiconductor material is silicon.
14. The device of claim 13 wherein the chemical component includes one or more of germanium or carbon.
15. A device, comprising:
a substrate;
a fin on the substrate, the fin including:
an upper portion;
a base region made of a strain-inducing compound, the base region inducing strain in the upper portion;
a source region;
a drain region; and
a channel in the upper portion of the fin, the channel extending between the source region and the drain region;
a gate structure that wraps around three sides of the channel; and
an insulating layer between the substrate and the base region of the fin, the insulating layer separating the fin and the gate structure from the substrate.
16. The device of claim 15 wherein the gate structure further includes a metal gate electrode spaced apart from the upper portion of the fin by a gate dielectric.
17. The device of claim 15 wherein the strain-inducing compound includes one or more of SiGe or SiC.
18. The device of claim 17 wherein a component of the strain-inducing compound has a non-uniform concentration across the base region.
19. The device of claim 18 wherein the component has a lower concentration in a center of the base region than at edges of the base region.
20. The device of claim 15 wherein the substrate is made of silicon, the insulating layer is made of oxide, and the device is a silicon-on-insulator finFET.