Controlled faceting of source/drain regions
View Patent ↗Numerous embodiments of a method for highly selective faceting of the S/D regions in a CMOS device are described. In one embodiment, source/drain regions are formed on a substrate. The source/drain regions are wet etched to form faceted regions. A silicon germanium layer is formed on the faceted regions of the source/drain regions to yield a strained device.
1. A method, comprising:
forming source/drain regions on a substrate;
etching the source/drain regions to form faceted regions;
forming a silicon germanium layer on the faceted regions of the source/drain regions; and
depositing a silicon layer above the silicon germanium layer to form a strained device, wherein anisotropic wet etching allows for controlled faceting of the source/drain regions based on a crystal density and a crystal orientation of the source/drain regions.
2. A method, comprising:
forming source/drain regions on a substrate;
anisotropic wet-etching the source/drain regions to form faceted regions;
forming a silicon germanium layer on the faceted regions of the source/drain regions,
wherein the faceted regions have an etch-out angle of about 120 degrees to about 130 degrees.
3. A method, comprising:
wet etching a source/drain region of a substrate with an etch solution having about 2 percent to about 30 percent ammonium hydroxide by volume;
forming a facet region in the source/drain region;
layering the facet region with silicon germanium; and
depositing silicon above silicon germanium.
4. The method of claim 3 , wherein the etch solution has a pH of about 9 to about 11.
5. The method of claim 4 , wherein the etch solution has a temperature of about 15° C. to about 60° C.
6. A method, comprising:
wet etching a source/drain region of a substrate with an etch solution having about 10 percent to about 30 percent tetra methyl ammonium by volume;
forming a facet region in the source/drain region;
layering the facet region with silicon germanium; and
depositing silicon above silicon germanium.
7. The method of claim 6 , wherein the etch solution has a temperature of about 20° C. to about 45° C.
8. A method, comprising:
wet etching a source/drain region of a substrate to an etch depth of about 100 Angstroms to about 500 Angstroms;
forming a facet region in the source/drain region;
layering the facet region with silicon germanium; and
depositing silicon above silicon germanium.
9. The method of claim 3 , wherein the etch solution is based on a crystal density and a crystal orientation of the substrate.
10. The method of claim 6 , wherein the etch solution is based on a crystal density and a crystal orientation of the substrate.
11. The method of claim 6 , wherein wet etching further comprises sonicating the wet etch solution.
12. A method, comprising:
providing a substrate having a source/drain region, a gate electrode disposed above the substrate, and a channel region formed below the gate electrode;
etching the source/drain region to form a faceted region near the channel region with an etch solution of about 10 percent to about 30 percent tetra methyl ammonium hydroxide by volume;
layering the faceted region with silicon germanium; and
depositing silicon above the silicon germanium.