Method for forming a strained semiconductor layer including replacing an etchable material formed under the strained semiconductor layer with a dielectric layer
A semiconductor device comprising a substrate having a region protruding from the substrate surface; a relaxed semiconductor disposed on the region; an additional semiconductor disposed on the relaxed semiconductor; and low density dielectric disposed next to and at least partially underneath the relaxed semiconductor and adjacent to the protruding region of the substrate.
1. A method of making a semiconductor device comprising:
forming a strained germanium layer on a horizontal surface of a recessed region of a substrate, wherein the substrate comprises a region protruding from the horizontal substrate surface adjacent to the recessed region;
forming strained silicon germanium on the strained germanium layer having a defect density less than 1×10 6 /cm 3 ;
applying mask material to the strained silicon germanium layer;
forming a trench in the strained silicon germanium layer;
removing the strained germanium layer to form a continuous cavity, wherein at least a portion of the continuous cavity is positioned between the horizontal surface of the recessed region and the strained silicon germanium layer;
filling the continuous cavity with a low density silicon oxide; and
heating the device to a temperature of 500° C. to 1300° C. to form a relaxed silicon germanium layer having a defect density less than 1×10 6 /cm 3 ; and
forming an additional semiconductor on the relaxed silicon germanium layer, wherein the additional semiconductor is a strained semiconductor.
2. The method of claim 1 , wherein the low density silicon dioxide has a density of 1.5 g/cm 3 to 3 g/cm 3 .
3. The method of claim 1 , wherein the annealing heating occurs for 1 second to 3 hours at a temperature of 500 to 1300° C.
4. The method of claim 1 , wherein the relaxed silicon germanium layer has a germanium content of 20 to 25 mole %.
5. The method of claim 1 , wherein the additional semiconductor comprises silicon.
6. The method of claim 5 , wherein the second additional semiconductor is tensilely strained.
7. A method of making a semiconductor device comprising:
applying a mask material to a first region on a substrate;
removing substrate from an unmasked substrate region adjacent to the first region to form a recessed region comprising a horizontal substrate surface and a region protruding from the horizontal substrate surface, wherein the region protruding from the horizontal substrate surface comprises the first region;
forming a selectively etchable material in the recessed region on the horizontal substrate surface;
removing the mask material from the first region;
forming a strained semiconductor layer on the selectively etchable material and first region having a defect density less than 1×10 6 /cm 3 , wherein the strained semiconductor layer does not contact the horizontal substrate surface;
applying mask material to the strained semiconductor layer;
forming a trench in the strained semiconductor layer at a distance from the first region wherein the trench extends through the selectively etchable material to the substrate;
removing the selectively etchable material after forming the trench to form a continuous cavity comprising the trench and the area resulting from the removed selectively etchable material, wherein at least a portion of the continuous cavity is positioned between the horizontal substrate surface and the strained semiconductor;
filling the continuous cavity with a low density dielectric;
heating the device to a temperature of 500° C. to 1300° C. to form a relaxed semiconductor layer; and
forming an additional semiconductor on the relaxed semiconductor, wherein the additional semiconductor is a strained semiconductor.
8. The method of claim 7 , wherein the selectively etchable material has a thickness of 1 to 5 nanometers.
9. The method of claim 7 , wherein the low density dielectric comprises silicon dioxide having a density of 1.5 g/cm 3 to 3 g/cm 3 .
10. The method of claim 7 , wherein the heating occurs for 1 second to 3 hours at a temperature of 500 to 1300° C.
11. The method of claim 7 , wherein the relaxed semiconductor layer is silicon germanium having 20 to 25 mole % germanium and the additional semiconductor is silicon germanium having 40 to 50 mole % germanium.
12. The method of claim 7 , wherein the selectively etchable material comprises germanium.
13. The method of claim 7 , further comprising:
applying the mask material to a second region on the substrate, wherein the mask material is adjacent to a second unmasked substrate region;
removing substrate from the second unmasked substrate region adjacent to the second region to form a second recessed region;
forming the selectively etchable material in the second recessed region;
removing the second mask material from the second region;
forming the strained semiconductor layer on the selectively etchable material and second region;
applying a second mask material to the strained semiconductor layer; and
forming the trench in the strained semiconductor layer at a distance from the first region and the second region wherein the trench extends through the selectively etchable material to the substrate.
14. The method of claim 7 , wherein the additional semiconductor comprises silicon germanium.
15. The method of claim 14 , wherein the additional semiconductor is compressively strained.