Source/drain stressor having enhanced carrier mobility manufacturing same
View Patent ↗Various source/drain stressors that can enhance carrier mobility, and methods for manufacturing the same, are disclosed. An exemplary source/drain stressor includes a seed layer of a first material disposed over a substrate of a second material, the first material being different than the second material; a relaxed epitaxial layer disposed over the seed layer; and an epitaxial layer disposed over the relaxed epitaxial layer.
1. A semiconductor device comprising:
a substrate of a first material;
a gate stack disposed over the substrate, the gate stack interposing a source region and a drain region of the substrate;
and a strained feature formed in the substrate in the source and drain regions, wherein the strained feature includes:
a seed layer of a second material disposed over the substrate, the second material being different than the first material, a relaxed epitaxial layer disposed over the seed layer, and an epitaxial layer disposed over the relaxed epitaxial layer;
wherein the seed layer is a silicon carbon layer;
the substrate is a silicon substrate;
the relaxed epitaxial layer is a relaxed silicon germanium epitaxial layer; and
the epitaxial layer is a silicon-containing epitaxial layer.
2. The semiconductor device of claim 1 wherein a lattice constant of the seed layer varies from a lattice constant of the substrate by about 0.06 Å to about 0.20 Å.
3. The semiconductor device of claim 1 wherein a lattice constant of the relaxed epitaxial layer varies from a lattice constant of the substrate by about 0.04 Å to about 0.12 Å.
4. The semiconductor device of claim 3 wherein a lattice constant of the epitaxial layer is substantially the same as the lattice constant of the relaxed epitaxial layer.
5. The semiconductor device of claim 1 wherein the seed layer is a relaxed silicon germanium layer having a germanium concentration that is greater than a germanium concentration of the relaxed silicon germanium epitaxial layer.
6. The semiconductor device of claim 5 wherein the germanium concentration of the relaxed silicon germanium epitaxial layer is at least 10% less than the germanium concentration of the relaxed silicon germanium layer.
7. The semiconductor device of claim 1 wherein a carbon concentration of the silicon carbon layer is about 2% to about 5%.
8. A semiconductor device comprising:
a substrate of a first material;
a gate stack disposed over the substrate, the gate stack interposing a source region and a drain region of the substrate;
and a strained feature formed in the substrate in the source and drain regions, wherein the strained feature includes:
a seed layer of a second material disposed over the substrate, the second material being different than the first material, a relaxed epitaxial layer disposed over the seed layer, and an epitaxial layer disposed over the relaxed epitaxial layer;
wherein the seed layer is a carbon coherence breaking layer;
the substrate is a silicon substrate;
the relaxed epitaxial layer is a relaxed silicon germanium epitaxial layer; and
the epitaxial layer is a silicon-containing epitaxial layer.
9. The semiconductor device of claim 8 wherein a lattice constant of the seed layer varies from a lattice constant of the substrate by about 0.06 Å to about 0.20 Å.
10. The semiconductor device of claim 8 wherein a lattice constant of the relaxed epitaxial layer varies from a lattice constant of the substrate by about 0.04 Å to about 0.12 Å.
11. The semiconductor device of claim 10 wherein a lattice constant of the epitaxial layer is substantially the same as the lattice constant of the relaxed epitaxial layer.
12. The semiconductor device of claim 8 wherein the seed layer is a relaxed silicon germanium layer having a germanium concentration that is greater than a germanium concentration of the relaxed silicon germanium epitaxial layer.
13. The semiconductor device of claim 12 wherein the germanium concentration of the relaxed silicon germanium epitaxial layer is at least 10% less than the germanium concentration of the relaxed silicon germanium layer.