Reusable nitride wafer, method of making, and use thereof
Techniques for processing materials for manufacture of gallium-containing nitride substrates are disclosed. More specifically, techniques for fabricating and reusing large area substrates using a combination of processing techniques are disclosed. The methods can be applied to fabricating substrates of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, and others. Such substrates can be used for a variety of applications including optoelectronic devices, lasers, light emitting diodes, solar cells, photo electrochemical water splitting and hydrogen generation, photo detectors, integrated circuits, transistors, and others.
1. A method for re-using a used crystalline nitride wafer from which a layer has been removed, said used crystalline nitride wafer having a diameter greater than about 25 millimeters and a thickness between about 100 micrometers and about 10 millimeters, a substantially wurtzite structure, a first surface from which said layer was removed, said first surface having a root-mean-square surface roughness greater than about 10 nanometers measured over an area of 20 micrometers by 20 micrometers; and a second surface opposite said first surface and having a root-mean-square surface roughness less than about 10 micrometers measured over an area of at least 20 micrometers by 20 micrometers, said method comprising:
preparing at least one of said first surface and said second surface for re-growth to form a planarized substrate;
performing bulk crystal growth on said planarized substrate to form a regrown wafer; and
preparing a regrowth surface on said regrown wafer to an epi-ready state, said regrowth surface having a surface threading dislocation density less than about 10 7 cm −2 , a stacking-fault concentration below about 10 2 cm −1 , and a symmetric x-ray rocking curve full width at half maximum (FWHM) less than about 100 arcsec, and a root-mean-square surface roughness less than about 0.5 nanometers measured over an area of 20 micrometers by 20 micrometers.
2. The method of claim 1 , wherein preparing at least one of said first surface and said second surface for re-growth comprises at least one of grinding, lapping, polishing, dry etching, wet etching, and chemical-mechanical polishing.
3. The method of claim 2 , wherein preparing at least one of said first surface and said second surface for re-growth comprises removal of a residual device layer.
4. The method of claim 1 , wherein said first surface is prepared for regrowth and said bulk crystal growth is performed on that surface.
5. The method of claim 1 , wherein said second surface is prepared for regrowth and said bulk crystal growth is performed on that surface.
6. The method of claim 1 , wherein bulk crystal growth on said planarized substrate is performed by at least one of hydride vapor phase epitaxy, metalorganic chemical vapor deposition, molecular beam epitaxy, ammonothermal growth, or flux growth.
7. The method of claim 1 , wherein said bulk crystal growth is performed with at least a second used wafer having a second planarized substrate, wherein said planarized substrate is positioned back-to-back with said second planarized substrate with a separation of less than 3 millimeters.
8. The method of claim 1 , wherein said regrowth surface is prepared by at least one of grinding, lapping, polishing, dry etching, wet etching, and chemical-mechanical polishing.
9. The method of claim 1 , further comprising performing one or more of edge-grinding, beveling, or flat-grinding to said regrown wafer.
10. The method of claim 1 , further comprising heating said regrown wafer to a temperature between 800 degrees Celsius and 1100 degrees Celsius for a time between 30 minutes and 10 hours in an atmosphere comprising at least one of ammonia, hydrogen, and nitrogen at a pressure between 100 Torr and 1000 Torr.
11. The method of claim 1 , wherein said regrowth surface has a crystallographic orientation within 5 degrees, within 2 degrees, within 1 degree, within 0.5 degree, within 0.2 degree, within 0.1 degree, within 0.05 degree, within 0.02 degree, or within 0.01 degree of (0001)+c-plane, (000-1) −c-plane, {10-10} m-plane, {11-20} a-plane, {11-2.+−.2}, {30-3.+−.1}, {20-2.+−.1}, {30-3.+−.2}, {10-1.+−.1}, or {10-1.+−.2}.
12. The method of claim 11 , wherein said regrowth surface has a crystallographic orientation that is miscut from the (0001)+c-plane by between about 0.2 degrees and about 1 degree toward a <10-10>m-direction and by less than 1 degree toward an orthogonal <11-20>a-direction.
13. The method of claim 1 , wherein said regrown wafer has a total thickness variation (TTV) of less than about 10 micrometers and by a macroscopic bow that is less than about 100 micrometers.
14. The method of claim 1 , wherein said regrown wafer has a variation in a miscut angle across said regrowth surface that is less than about 2 degrees in each of two orthogonal crystallographic directions.
15. The method of claim 1 , wherein said regrowth surface has an edge perimeter that is substantially round, with at least one orientation flat.
16. The method of claim 1 , wherein said layer is removed by spalling.