Method of forming a seed area and growing a heteroepitaxial layer on the seed area
A method for making a heteroepitaxial layer. The method comprises providing a semiconductor substrate. A seed area delineated with a selective growth mask is formed on the semiconductor substrate. The seed area comprises a first material and has a linear surface dimension of less than 100 nm. A heteroepitaxial layer is grown on the seed area, the heteroepitaxial layer comprising a second material that is different from the first material. Devices made by the method are also disclosed.
1. A method for making a heteroepitaxial layer, the method comprising:
providing a semiconductor substrate;
forming a nanostructured pedestal comprising silicon on the semiconductor substrate, the pedestal having a top surface and a side surface;
providing a conformal selective growth mask layer on the top surface and side surface of the pedestal, wherein the selective growth mask comprises an oxidized side surface of the pedestal, the width of the pedestal having been reduced compared to the width of the pedestal prior to providing the conformal selective growth mask layer;
removing a portion of the selective growth mask layer to expose the top surface of the pedestal, wherein removing the portion of the selective growth mask layer comprises forming a non-conformal layer over the selective growth mask layer and etching the non-conformal layer and the selective growth mask layer;
selectively etching-back the exposed top surface of the pedestal to form a seed area having a (001) facet, the seed area having a first linear surface dimension that ranges from about 10 nm to about 50 nm and a second linear surface dimension that ranges from about 200 nm to about 5000 nm; and
growing the heteroepitaxial layer on the seed area without nucleating substantially any threading dislocations, at least a portion of the heteroepitaxial layer extending above the growth mask and having a width dimension that is wider than a corresponding width dimension of the seed area,
wherein a portion of the heteroepitaxial layer above the selective growth mask layer has a polygonal cross-sectional shape.
2. The method of claim 1 , wherein the exposed top surface is etched back such that it forms a seed area that is approximately coplanar with a top surface of the selective growth mask layer.
3. The method of claim 1 , wherein the heteroepitaxial layer is substantially defect-free.
4. The method of claim 1 , wherein the heteroepitaxial layer slopes outward proximate the seed area.
5. A method for making a heteroepitaxial layer, the method comprising:
providing a semiconductor substrate;
forming a nanostructured pedestal comprising silicon on the semiconductor substrate, the pedestal having a top surface and a side surface;
providing a conformal selective growth mask layer on the top surface and side surface of the pedestal, wherein the selective growth mask comprises an oxidized side surface of the pedestal, the width of the pedestal having been reduced compared to the width of the pedestal prior to providing the conformal selective growth mask layer;
removing a portion of the selective growth mask layer to expose the top surface of the pedestal, wherein removing the portion of the selective growth mask layer comprises forming a non-conformal layer over the selective growth mask layer and etching the non-conformal layer and the selective growth mask layer;
selectively etching-back the exposed top surface of the pedestal to form a seed area having a (001) facet, the seed area having a first linear surface dimension that ranges from about 10 nm to about 50 nm and a second linear surface dimension that ranges from about 200 nm to about 5000 nm; and
growing the heteroepitaxial layer on the seed area without nucleating substantially any threading dislocations, at least a portion of the heteroepitaxial layer extending above the growth mask and having a width dimension that is wider than a corresponding width dimension of the seed area,
wherein the heteroepitaxial layer slopes outward proximate the seed area and slopes inward distal from the seed area.
6. The method of claim 1 , wherein the entire heteroepitaxial layer is grown above a top surface of the selective growth mask layer.
7. The method of claim 1 , wherein the semiconductor substrate is comprised of silicon.
8. The method of claim 1 , wherein the semiconductor substrate comprises silicon having a [001] direction normal to the substrate surface.
9. The method of claim 1 , wherein the selective growth mask layer is comprised of silicon dioxide.
10. The method of claim 1 , further comprising forming a portion of a transistor from the heteroepitaxial layer.
11. A method for making a heteroepitaxial layer, the method comprising:
providing a semiconductor substrate;
forming a nanostructured pedestal comprising silicon on the semiconductor substrate, the pedestal having a top surface and a side surface;
providing a conformal selective growth mask layer on the top surface and side surface of the pedestal, wherein the selective growth mask comprises an oxidized side surface of the pedestal, the width of the pedestal having been reduced compared to the width of the pedestal prior to providing the conformal selective growth mask layer;
removing a portion of the selective growth mask layer to expose the top surface of the pedestal;
selectively etching-back the exposed top surface of the pedestal to form a seed area having a (001) facet, the seed area having a linear surface dimension that ranges from about 10 nm to about 50 nm; and
growing the heteroepitaxial layer on the seed area without nucleating substantially any threading dislocations, at least a portion of the heteroepitaxial layer extending above the growth mask and having a width dimension that is wider than a corresponding width dimension of the seed area,
wherein a portion of the heteroepitaxial layer above the selective growth mask layer has a polygonal cross-sectional shape.
12. The method of claim 11 , wherein the heteroepitaxial layer is substantially defect-free.
13. The method of claim 11 , wherein the heteroepitaxial layer slopes outward proximate the seed area.
14. A method for making a heteroepitaxial layer, the method comprising:
providing a semiconductor substrate;
forming a nanostructured pedestal comprising silicon on the semiconductor substrate, the pedestal having a top surface and a side surface;
providing a conformal selective growth mask layer on the top surface and side surface of the pedestal, wherein the selective growth mask comprises an oxidized side surface of the pedestal, the width of the pedestal having been reduced compared to the width of the pedestal prior to providing the conformal selective growth mask layer;
removing a portion of the selective growth mask layer to expose the top surface of the pedestal;
selectively etching-back the exposed top surface of the pedestal to form a seed area having a (001) facet, the seed area having a linear surface dimension that ranges from about 10 nm to about 50 nm; and
growing the heteroepitaxial layer on the seed area without nucleating substantially any threading dislocations, at least a portion of the heteroepitaxial layer extending above the growth mask and having a width dimension that is wider than a corresponding width dimension of the seed area,
wherein the heteroepitaxial layer slopes outward proximate the seed area and slopes inward distal from the seed area.
15. The method of claim 11 , wherein the entire heteroepitaxial layer is grown entirely above a top surface of the selective growth mask layer.
16. The method of claim 11 , wherein the semiconductor substrate is comprised of silicon.
17. The method of claim 11 , wherein the semiconductor substrate comprises silicon having a [001] direction normal to the substrate surface.
18. The method of claim 11 , wherein the seed area has a second linear surface dimension that ranges from about 200 nm to about 5000 nm.
19. The method of claim 11 , further comprising forming a portion of a transistor from the heteroepitaxial layer.
20. The method of claim 1 , wherein the growing the heteroepitaxial layer on the seed area occurs without nucleating any threading dislocations.
21. The method of claim 11 , wherein the growing the heteroepitaxial layer on the seed area occurs without nucleating any threading dislocations.
22. The method of claim 1 , wherein the heteroepitaxial layer comprises germanium.
23. The method of claim 1 , wherein the heteroepitaxial layer comprises Ge 0.23 Si 0.77 .
24. The method of claim 1 , wherein the heteroepitaxial layer comprises a III-V material chosen from Group III-N semiconductors, GaAs, InAs and InAsSb.
25. The method of claim 1 , wherein the heteroepitaxial layer comprises a III-V material.