Claims
- 1. A method of producing single-crystal structures with cantilevered web features on a single-crystal substrate, said method comprising the steps of:
(a) choosing a single crystal substrate material which exhibits the property that the material contains at least one growth plane orientation whereby under selected growth conditions the growth rate due to step-flow growth is greater than at least one hundred (100) times a growth rate due to growth involving two-dimensional nucleation; (b) preparing a planar first growth surface on said substrate that is parallel to within a predetermined angle relative to a selected crystal plane of said substrate; (c) removing material in said first growth surface so as to define at least one selected separated second growth surface defined by a boundary wherein said boundary has at least one concave border; (d) treating said substrate so as to remove any removable sources of unwanted crystal nucleation and any removable sources of steps; (e) depositing a homoepitaxial film on said second separated growth surface under selected conditions so as to provide a step-flow growth while suppressing two-dimensional nucleation; (f) continuing said deposition of said homoepitaxial film so that said step-flow growth results and produces a cantilevered web structure growing from said at least one of the concave border; and (g) continuing said deposition of said homoepitaxial film until a third selected separated growth surface of a desired size and shape is achieved.
- 2. The method according to claim 1, wherein said selected crystal plane is the basal plane.
- 3. The method according to claim 1, wherein said predetermined angle is less than 1 degree.
- 4. The method according to claim 3, wherein said at least one selected separated second growth surface comprises an array of separated second growth surfaces.
- 5. The method according to claim 4, wherein said single-crystal substrate is selected from the group consisting of 6H—SiC; 4H—SiC; 15R—SiC; 2H—GaN; and 2H—AlN.
- 6. The method of claim 5, wherein said selected boundary shape is formed by the joining of selected simple branch shapes to form said concave border that promotes web growth.
- 7. The method of claim 6, wherein said selected branch shapes each have a length dimension greater than the width dimension of said selected branch shapes.
- 8. The method according to claim 1, wherein a planar area of said second growth surface boundary is selected to be less than ten times the mathematical inverse of a density of non-removable step sources contained in said substrate.
- 9. The method of claim 7, wherein said selected branch shapes are selected to be joined in one or more of the following configurations that provide for one or more concave border portions that promote web growth; a V-shape; a U-shape; a multiple joined V-shape; a multiple joined U-shape; and a tree; and combinations thereof.
- 10. The method according to claim 9, wherein a planar area of said second growth surface boundary is selected to be less than ten times the mathematical inverse of a density of non-removable step sources contained in said substrate.
- 11. The method according to claim 10, wherein a size area of completed resulting web growth structure is selected to be a size of a desired area and shape.
- 12. The method according to claim 9, wherein said selected branch shapes of said configurations are oriented so that their lengths lie parallel in a direction selected from the group consisting of crystal vertex and crystal facet directions.
- 13. The method according to claim 12, wherein an orientation of said selected shape configurations is selected so that the root of the said selected shape configuration contains the highest initial crystal seed plane of the said second selected separated surface.
- 14. The method according to claim 13, wherein all branches flow toward a general down-step direction.
- 15. The method according to claim 14, wherein an atomically flat epitaxial film surface is obtained where said atomically flat surface is parallel to said selected crystal plane.
- 16. The method according to claim 15 further comprising the steps of:
(h) depositing a desired heteroepitaxial film on said atomically flat epitaxial film surface under predetermined conditions that preferably cause two-dimensional nucleation accompanied by step-flow growth of said desired heteroepitaxial film; and (i) continuing said depositing of said step (h) until a desired thickness is obtained.
- 17. The method according to claim 16 further comprising the steps of growing multiple heteroepitaxial films.
- 18. The method according to claim 10, wherein an atomically flat epitaxial film surface is obtained where said atomically flat surface is parallel to said selected crystal plane.
- 19. The method according to claim 18 further comprising the steps of:
(h) depositing a desired heteroepitaxial film on said atomically flat epitaxial film surface under predetermined conditions that preferably cause two-dimensional nucleation accompanied by step-flow growth of said desired heteroepitaxial film; and (i) continuing said depositing of said step (h) until a desired thickness is obtained.
- 20. The method according to claim 19 further comprising the steps of growing multiple heteroepitaxial films.
- 21. The method according to claim 12, wherein an atomically flat epitaxial film surface is obtained where atomically flat surface is parallel to said selected crystal plane.
- 22. The method according to claim 21 further comprising the steps of:
(h) depositing a desired heteroepitaxial film on said atomically flat epitaxial film surface under predetermined conditions that preferably cause two-dimensional nucleation accompanied by step-flow growth of said desired heteroepitaxial film; and (i) continuing said depositing of said step (h) until a desired thickness is obtained.
- 23. The method according to claim 22 further comprising the steps of growing multiple heteroepitaxial films.
- 24. The method according to claim 1, wherein said steps (a)-(g) of claim 1 provide said cantilevered web structure that is used to produce a product which has a semiconductor device structure.
- 25. The method according to claim 1, wherein said steps (a)-(g) of claim 1 provide said cantilevered web structure that is used to produce a micromachined device.
- 26. A method for producing cantilevered atomically-flat top surfaces on single-crystal substrates, said method comprising the steps of:
(a) choosing a single crystal substrate material which exhibits the property that the material contains at least one growth plane orientation whereby under selected growth conditions the growth rate due to step-flow growth is greater than at least one hundred (100) times a growth rate due to growth involving two-dimensional nucleation; (b) preparing a planar first growth surface on said substrate that is parallel to within a predetermined angle relative to a selected crystal plane of said substrate; (c) removing material in said first growth surface so as to define at least one selected separated second growth surface defined by a single continuous boundary; (d) depositing a homoepitaxial film on said second separated growth surface under selected conditions so as to provide a step-flow growth while suppressing two-dimensional nucleation; (e) continuing said deposition of said homoepitaxial film so that said step-flow growth results and produces a cantilevered structure growing on said second growth surface; and (f) continuing said deposition of said homoepitaxial film until a cantilevered structure with atomically flat surface of a desired size and shape is achieved.
- 27. The method according to claim 26 further comprising an added step occurring before step (c) and after step (b), said added step comprising, treating said substrate so as to remove any removable sources of unwanted crystal nucleation and remove any removable unwanted sources of steps.
- 28. The method of claim 26, wherein said at least one separated selected growth surface comprises an array of separated areas.
- 29. The method of claim 28, wherein a size of said separated areas is approximately equal to that of one of desired semiconductor devices and integrated circuits.
- 30. The method of claim 26, wherein said any source of unwanted crystal nucleation are contributed to by said single crystal substrate and by said steps (a) and (b).
- 31. The method of claim 26, wherein said any source of unwanted steps are contributed to by said crystal substrate and steps (a) and (b).
- 32. The method according to claim 26, wherein said single crystal substrate is selected from the group comprising polytypes of silicon carbide.
- 33. The method according to claim 26 further comprising the steps:
(g) depositing a desired heteroepitaxial film on said homoepitaxial film under predetermined conditions that preferably cause two-dimensional nucleation accompanied by step-flow growth of said desired heteroepitaxial film; and (h) continuing said depositing of said step (s) of said heteroepitaxial film until a desired thickness is obtained.
- 34. The method according to claim 26, wherein said predetermined angle is less than 1 degree.
- 35. The method according to claim 26, wherein the said single-crystal substrate is alpha-SiC.
- 36. The method according to claim 35, wherein the said single-crystal substrate is 6H—SiC.
- 37. The method according to claim 35, wherein the said single-crystal substrate is 4H—SiC.
- 38. The method according to claim 33, wherein the said heteroepitaxial film is 3C—SiC.
- 39. The method according to claim 33, wherein said heteroepitaxial film is a III-Nitride compound.
- 40. The method according to claim 39, wherein the said heteroepitaxial film is GaN.
- 41. The method according to claim 39, wherein the said heteroepitaxial film is AlN.
- 42. The method according to claim 39, wherein the said heteroepitaxial film is AlGaN.
- 43. The method according to claim 25, wherein said added step is subjected to an etch in a gaseous mixture of hydrogen chloride and hydrogen at a temperature greater than 1000° C. to remove sources of removable unwanted crystal nucleation.
- 42. The method according to claim 24, wherein said step (b) is accomplished by forming trenches.
- 43. The method according to claim 24, wherein said step (b) is accomplished by physical means.
- 44. The method according to claim 43, wherein said physical means is selected from the group comprising photolithography, laser etching, ion etching, photochemical etching, electrochemical etching, and photoelectrochemical etching.
- 45. The method according to claim 24, wherein said step (b) is accomplished by cutting the said substrate apart.
- 46. The method according to claim 31, wherein said heteroepitaxial film comprises SiC and said method further comprising the steps:
(i) continuing the growth of the said heteroepitaxial film under selected conditions so as to provide a step-flow growth while suppressing two-dimensional nucleation; and (j) continuing said deposition of said heteroepitaxial film until said step-flow growth produces atomically-flat epitaxial film surface and cantilevered growth on each of said at least one separated area where said atomically-flat surface is parallel to said selected crystal plane.
- 47. The method according to claim 46, wherein said multiple heteroepitaxial films comprise adjacent layers that are brought together with a buffer layer that reduces the stress between adjacent layers.
- 48. The method according to claim 24, wherein said steps (a)-(d) of claim 1 provide said atomically-flat surface that is used to produce a product which has a semiconductor device structure.
- 49. The method according to claim 24, wherein said selected crystal plane is the basal (0001) plane.
Government Interests
[0001] The invention described herein was made by employees of the United States Government and may be used by or for the Government for governmental purposes without payment of any royalties thereon or therefor.