Strained silicon finFET device
Disclosing is a strained silicon finFET device having a strained silicon fin channel in a double gate finFET structure. The disclosed finFET device is a double gate MOSFET consisting of a silicon fin channel controlled by a self-aligned double gate for suppressing short channel effect and enhancing drive current. The silicon fin channel of the disclosed finFET device is a strained silicon fin channel, comprising a strained silicon layer deposited on a seed fin having different lattice constant, for example, a silicon layer deposited on a silicon germanium seed fin, or a carbon doped silicon layer deposited on a silicon seed fin. The lattice mismatch between the silicon layer and the seed fin generates the strained silicon fin channel in the disclosed finFET device to improve hole and electron mobility enhancement, in addition to short channel effect reduction characteristic inherently in a finFET device.
1. A method of fabricating a strained silicon finFET device, comprising the steps of:
a) providing a silicon on insulator substrate having a silicon surface having a silicon-containing multilayer on an insulator layer;
a1) depositing a layer of SiGe onto the silicon on insulator substrate, the deposited SiGe having a parallel lattice constant in the directions parallel to the silicon surface and a perpendicular lattice constant in the direction perpendicular to the silicon surface,
wherein the parallel lattice constant being similar to the lattice constant of silicon and the perpendicular lattice constant being greater than the parallel lattice constant;
b) patterning the silicon and the SiGe multilayer into a source region and a drain region sandwiching a seed channel region, the seed channel being a seed fin structure having a parallel lattice constant and a greater perpendicular lattice constant;
c) depositing an epitaxial channel layer onto the seed fin structure, the channel layer material having a lattice constant smaller than that of the perpendicular lattice constant seed fin material, wherein the epitaxial channel layer becomes a tensile strained channel layer in the direction perpendicular to the silicon surface due to the lattice mismatch between the channel layer and the seed fin structure;
d) forming a gate dielectric layer on the epitaxial strained channel; and
e) forming a gate over the epitaxial strained channel.
2. The method as in claim 1 wherein the germanium content of the silicon germanium layer seed fin is between 10% to 100%.
3. The method as in claim 1 wherein the epitaxial channel layer is a silicon layer, a silicon germanium layer, a carbon doped silicon layer, or a carbon doped silicon germanium layer.
4. The method as in claim 1 wherein the patterning of the source, drain and channel regions from the multilayer comprises the steps of:
b1) providing a patterned mask on the multilayer;
b2) patterning the multilayer according to the patterned mask to define source, drain and channel regions; and
b3) removing the patterned mask.
5. The method as in claim 1 further comprising a step c1 after step c:
c1) doping the channel region.
6. The method as in claim 1 wherein the formation of the gate comprises the steps of:
e1) depositing a gate material layer;
e2) doping the gate material layer;
e3) providing a patterned mask on the gate material layer;
e4) patterning the gate material layer according to the patterned mask to define the gate; and
e5) removing the patterned mask.
7. The method as in claim 1 further comprising a step f after step e:
f) forming lightly doped region (LDD) and halo regions between the channel region and the source and drain regions.
8. The method as in claim 1 further comprising the following steps after step e:
g) forming dielectric spacers between the gate and the source and drain regions,
h) doping the source and drain regions,
i) forming salicide of the gate, source and drain regions.
9. The method as in claim 1 wherein the thickness of the first silicon-containing layer of the silicon on insulator substrate is between 5 nm to 20 nm.
10. The method as in claim 1 wherein the germanium content of the silicon germanium layer is between 10% to 50%.
11. The method as in claim 1 further comprising the following step after step a1)
a2) depositing wherein the top most layer of the multilayer comprises a hard mask layer onto the SiGe layer.
12. The method as in claim 1 wherein the height of the seed fin structure is between 10 nm to 200 nm.
13. The method as in claim 1 wherein the width of the seed fin structure is between 5 nm to 100 nm.
14. The method as in claim 1 wherein the thickness of the strained channel layer is between 5 nm to 15 nm.
15. A method of fabricating a strained silicon finFET device, comprising the steps of:
a) providing a silicon on insulator substrate having a silicon surface;
a1) depositing a layer of SiGe onto the silicon on insulator substrate, the deposited SiGe having a parallel lattice constant in the directions parallel to the silicon surface and a perpendicular lattice constant in the direction perpendicular to the silicon surface,
wherein the parallel lattice constant being similar to the lattice constant of silicon and the perpendicular lattice constant being greater than the parallel lattice constant;
b) patterning the silicon and the SiGe multilayer into a source region and a drain region sandwiching a seed channel region, the seed channel being a seed fin structure having a parallel lattice constant and a greater perpendicular lattice constant;
c) depositing an epitaxial silicon channel layer onto the seed fin structure, wherein the epitaxial silicon channel layer becomes a tensile strained silicon channel layer in the direction perpendicular to the silicon surface due to the lattice mismatch between the silicon channel layer and the seed fin structure;
d) forming a gate dielectric layer on the epitaxial strained channel; and
e) forming a gate over the epitaxial strained channel.