Method of chemical doping that uses CMOS-compatible processes
A method of Atomic Precision Advanced Manufacturing (APAM) is provided, in which a substrate is doped from a dopant precursor gas. The method involves covering a surface of the substrate with a hard mask, selectively removing material from the hard mask such that selected areas of the substrate surface are laid bare, exposing the laid-bare areas to the dopant precursor gas, and heating the substrate so as to incorporate dopant from the dopant precursor gas into the substrate surface.
1. A method of doping a substrate from a dopant precursor gas, comprising:
covering a surface of the substrate with a hard mask;
selectively removing material from the hard mask such that selected areas of the substrate surface are laid bare;
exposing the laid-bare areas to the dopant precursor gas;
heating the substrate so as to incorporate dopant from the dopant precursor gas into the substrate surface;
forming a locking layer over the substrate surface by deposition followed by recrystallization; and
epitaxially growing a cap layer of silicon over the substrate.
2. The method of claim 1 , wherein the selective removal of material from the hard mask is performed by sputtering.
3. The method of claim 1 , further comprising, after the selective removal of material from the hard mask, recrystallizing the surface of the substrate.
4. The method of claim 1 , wherein the hard mask that covers the substrate surface has regions of greater thickness, here denominated thick regions, and regions of lesser thickness, here denominated thin regions.
5. The method of claim 4 , wherein, in the step of selectively removing material, the substrate surface is laid bare beneath the thin regions but remains covered by the hard mask in the thick regions.
6. The method of claim 4 , further comprising defining the thick and thin regions by lithographic patterning before material is selectively removed from the hard mask.
7. The method of claim 4 , wherein the covering step comprises forming a first hard mask layer, selectively removing material from the first hard mask layer from regions designated as thin regions, and then forming a second hard mask layer at least in the thin regions.
8. The method of claim 7 , wherein the second hard mask layer is oxidatively grown.
9. The method of claim 1 , wherein the hard mask covering a surface of the substrate comprises silicon dioxide.
10. The method of claim 1 , wherein the hard mask covering a surface of the substrate comprises silicon nitride or silicon oxynitride.
11. The method of claim 1 , wherein the hard mask comprises at least two regions having different material compositions, and wherein the step of selectively removing material from the hard mask is performed, at least in part, such that one material composition of the hard mask is removed selectively, relative to at least one other material composition of the hard mask.
12. The method of claim 1 , wherein the substrate comprises silicon.
13. The method of claim 1 , wherein the substrate comprises germanium, a germanium-silicon alloy, gallium arsenide, indium arsenide, indium phosphide, or gallium nitride.
14. The method of claim 1 , wherein the substrate comprises diamond.
15. The method of claim 1 , wherein the dopant is phosphorus, and the exposing step comprises exposing the substrate surface to phosphine.
16. The method of claim 1 , wherein the dopant is boron, and the exposing step comprises exposing the substrate surface to boron trichloride or diborane.
17. The method of claim 1 , wherein:
the dopant is arsenic, and the exposing step comprises exposing the substrate surface to arsine, or
the dopant is gallium, and the exposing step comprises exposing the substrate surface to triethylgallium, or
the dopant is antimony, and the exposing step comprises exposing the substrate surface to triphenylstibine.
18. The method of claim 1 , wherein the dopant is aluminum, and the exposing step comprises exposing the substrate surface to alane, aluminum trichloride, trimethylaluminum, or dimethyl aluminum hydride.