Direct and sequential formation of monolayers of boron nitride and graphene on substrates
View Patent ↗The invention generally related to a method for preparing a layer of graphene directly on the surface of a substrate, such as a semiconductor substrate. The layer of graphene may be formed in direct contact with the surface of the substrate, or an intervening layer of a material may be formed between the substrate surface and the graphene layer.
1. A method of preparing a semiconductor substrate, the semiconductor substrate comprising two major, generally parallel surfaces, one of which is a front surface of the semiconductor substrate and the other of which is a back surface of the semiconductor substrate, and a circumferential edge joining the front and back semiconductor substrate surfaces, the method comprising:
forming a first metal film on the front surface of the semiconductor substrate, the first metal film comprising a front metal film surface, a back metal film surface, and a bulk metal region between the front and back metal film surfaces, wherein the back metal film surface of the first metal film is in contact with the front semiconductor substrate surface;
forming a layer of boron nitride between the front surface of the semiconductor substrate and the back metal film surface of the first metal film;
removing the first metal film;
depositing a layer comprising a carbon-rich polymer on the layer of boron-nitride;
forming a second metal film on the carbon-rich polymer layer, the second metal film comprising a front metal film surface, a back metal film surface, and a bulk metal region between the front and back metal film surfaces, wherein the back metal film surface of the second metal film is in contact with the layer comprising the carbon-rich polymer; and
heating the semiconductor substrate comprising the layer of boron-nitride, the layer comprising the carbon-rich polymer, and the second metal film thereon in the presence of hydrogen to a temperature sufficient to degrade the carbon-rich polymer layer; and
precipitating carbon atoms to thereby form a layer of graphene between the layer of boron nitride and the back metal film surface of the second metal film.
2. The method of claim 1 wherein the carbon-rich polymer is selected from the group consisting of polymethylmethacrylate (PMMA), polybutadiene, polystyrene, poly(acrylonitrile-co-butadiene-co-styrene) (ABS), polyethylene, polypropylene, poly(4′-vinylhexaphenylbenzene)s, and combinations thereof.
3. The method of claim 1 wherein the carbon-rich polymer layer has a thickness between about 1 nanometer and about 100 nanometers thick.
4. The method of claim 1 wherein the layer of boron nitride is formed by contacting the first metal film surface with a boron-containing gas and a nitrogen-containing gas at a temperature sufficient to in-diffuse boron atoms and nitrogen atoms into the bulk metal region of the first metal film; and cooling the semiconductor substrate comprising the first metal film such that boron and nitrogen precipitate out of the bulk metal region of the first metal film and form a layer of boron nitride between the back metal film surface of the first metal film and the front surface of the semiconductor substrate.
5. The method of claim 4 wherein the boron-containing gas is selected from the group consisting of diborane, trichloroborane, and trifluoroborane.
6. The method of claim 4 wherein the nitrogen-containing gas is selected from the group consisting of nitrogen and ammonia.
7. The method of claim 4 wherein the boron-containing gas and the nitrogen-containing gas is the same and the gas is selected from the group consisting of borazine, trichloroborazine, and ammonia-borane.
8. The method of claim 1 wherein the semiconductor substrate comprises a semiconductor wafer.
9. The method of claim 8 wherein the semiconductor wafer comprises a material selected from the group consisting of silicon, gallium arsenide, silicon carbide, silicon germanium, silicon nitride, silicon dioxide, and germanium, and combinations thereof.
10. The method of claim 1 wherein the front surface of the semiconductor substrate comprises a dielectric layer on the front surface thereof.
11. The method of claim 1 wherein the front surface of the semiconductor substrate comprises a silicon oxide layer on the front surface thereof.
12. The method of claim 1 wherein the front surface of the semiconductor substrates comprises a silicon oxide layer and a silicon nitride layer, wherein the silicon oxide layer is between the semiconductor substrate and the silicon nitride layer.
13. The method of claim 1 wherein the second metal film comprises a metal having a carbon solubility of at least about 0.05 atomic % at 1000° C.
14. The method of claim 1 wherein the second metal film comprises a metal having a carbon solubility of less than about 3 atomic % at 1000° C.
15. The method of claim 1 wherein the second metal film comprises a metal selected from the group consisting of nickel, copper, iron, platinum, palladium, ruthenium, cobalt and alloys thereof.
16. The method of claim 1 wherein the second metal film comprises nickel.
17. The method of claim 1 wherein the second metal film comprises copper.
18. A multilayer article comprising:
a semiconductor substrate comprising two major, generally parallel surfaces, one of which is a front surface of the semiconductor substrate and the other of which is a back surface of the semiconductor substrate, a circumferential edge joining the front and back surfaces, and a central plane between the front and back surfaces;
a layer of graphene in contact with the front surface of the semiconductor substrate; and
a layer of boron nitride in contact with the layer of graphene.
19. The multilayer article of claim 18 further comprising a second layer of graphene in contact with the layer of boron nitride.
20. The multilayer article of claim 18 wherein the semiconductor substrate comprises a semiconductor wafer.
21. The multilayer article of claim 20 wherein the semiconductor wafer comprises a material selected from the group consisting of silicon, gallium arsenide, silicon carbide, silicon germanium, silicon nitride, silicon dioxide, germanium, and combinations thereof.
22. The multilayer article of claim 21 wherein the front surface of the semiconductor substrate comprises a dielectric layer.
23. The multilayer article of claim 18 wherein the layer of boron nitride comprises between 2 and about 100 mono-atomically thick layers of boron nitride.