Method of growing epitaxial layers on a substrate
View Patent ↗An epitaxial growth method includes plasma treating a surface of a bulk crystalline Aluminum Nitride (AlN) substrate and subsequently heating the substrate in an ammonia-rich ambient to a temperature of above 1000° C. for at least 5 minutes without epitaxial growth. After heating the surface, a III-nitride layer is epitaxially grown on the surface.
1. An epitaxial growth method, comprising:
plasma treating a surface of a bulk crystalline Aluminum Nitride (AlN) substrate;
after the plasma treating, removing organics and metals from the surface using one or more chemical etchants;
after removing the organics and metals, heating the surface in an ammonia-rich ambient environment to a temperature of above 1000° C. for at least 5 minutes without epitaxial growth; and
after heating the surface, epitaxially growing a III-nitride layer on the surface.
2. The method of claim 1 further comprising, before plasma treating the surface, exposing the surface to at least one of acetone, methanol, isopropyl alcohol, sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid.
3. The method of claim 1 , wherein heating the surface comprises introducing H 2 into a reaction chamber that encloses the surface.
4. The method of claim 3 , wherein heating the surface comprises:
introducing the H 2 into the reaction chamber at a flow rate of greater than about 2 L/min; and
introducing NH 3 into the reaction chamber at a flow rate of greater than about 2 L/minute.
5. An epitaxial growth method, comprising:
plasma treating a surface of a bulk crystalline Aluminum Nitride (AlN) substrate, wherein plasma treating the surface comprises:
accelerating Ar plasma toward the surface; and
flowing a halogen-containing gas near the surface during a time that the Ar plasma is accelerated toward the surface;
after the plasma treating, removing organics and metals from the surface using one or more chemical etchants;
after removing the organics and metals, heating the surface in an ammonia-rich ambient environment to a temperature of above 1000° C. for at least 5 minutes without epitaxial growth; and
after heating the surface, epitaxially growing a III-nitride layer on the surface.
6. The method of claim 5 , wherein the halogen-containing gas comprises one or more of chlorine (Cl 2 ) and boron trichloride (BCl 3 ).
7. The method of claim 5 , wherein flowing the halogen-containing gas comprises:
flowing BCl 3 gas at a flow rate of about 2 cc/min;
flowing Cl 2 gas at a flow rate of about 8 cc/min; and
flowing Ar gas at a flow rate of about 5 cc/min.
8. The method of claim 5 , wherein accelerating the plasma toward the surface comprises generating Ar plasma using electron cyclotron resonance with one or more of a microwave power of about 350 W, a magnetic flux density of about 1200 gauss, an accelerator voltage of about 100 Volts, and a beam voltage of about 550 volts.
9. The method of claim 5 , further comprising:
orienting the surface substantially perpendicular to the Ar plasma that is accelerated toward the surface;
maintaining a temperature of the surface at about 25 degrees C. during the plasma treatment; and
rotating the surface around an axis normal to the surface at about 10 degrees per second.
10. The method of claim 1 , wherein plasma treating the surface comprises plasma treating the surface for about 30 minutes.
11. The method of claim 1 , wherein plasma treating the surface comprises plasma etching using an inductively coupled plasma.
12. The method of claim 1 , wherein plasma treating the surface comprises plasma etching using a chemically-assisted ion beam.
13. The method of claim 1 , wherein plasma treating comprises plasma treating until about 360 nm of substrate material is removed from the surface.
14. The method of claim 1 , wherein removing the organics and metals from the surface using one or more chemical etchants comprises chemical processing using one or more of sulfuric, phosphoric, nitric, and hydrochloric acid.
15. The method of claim 14 , wherein chemical processing comprises chemical processing in sulfuric and phosphoric acid in a 3:1 solution heated to about 95 degrees C. for at least about 15 minutes.
16. The method of claim 1 , wherein the epitaxially grown III-nitride layer comprises InyAlxGa1-x-yN, wherein 0≦x≦1, 0≦y≦1.
17. The method of claim 1 , wherein an exposed surface of the epitaxially grown III-nitride layer has a surface roughness less than about 10 nm.
18. An epitaxial growth method, comprising:
plasma treating a surface of a bulk crystalline Aluminum Nitride (AlN) substrate, comprising:
accelerating Ar plasma toward the surface; and
flowing a halogen-containing gas comprising one or more of chlorine and boron trichloride near the surface during a time that the Ar plasma is accelerated toward the surface;
after the plasma treating, removing organics and metals from the surface using one or more chemical etchants;
after removing the organics and metals, heating the surface in an ammonia-rich ambient environment to a temperature of above 1000° C. for at least 5 minutes without epitaxial growth; and
after heating the surface, epitaxially growing an In y AlxGa 1-x-y N layer on the surface, wherein 0≦x≦1 and 0≦y≦1.
19. The method of claim 18 , wherein an exposed surface of the In y Al x Ga 1-x-y N layer has a surface roughness less than about 10 nm.
20. An epitaxial growth method, comprising:
exposing a surface of a bulk crystalline Aluminum Nitride (AlN) substrate to at least one of acetone, methanol, isopropyl alcohol, sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid;
after exposing the surface, plasma treating the surface;
after plasma treating the surface, removing organics and metals from the surface using one or more chemical etchants;
after removing the organics and metals, heating the surface in an ammonia-rich ambient environment to a temperature of above 1000° C. for at least 5 minutes without epitaxial growth; and
after heating the surface, epitaxially growing a III-nitride layer on the surface.
21. The method of claim 20 , wherein plasma treating the surface comprises:
accelerating Ar plasma toward the surface while flowing a halogen-containing gas near the surface.
22. The method of claim 21 , wherein flowing the halogen-containing gas comprises:
flowing BCl 3 gas at a flow rate of about 2 cc/min;
flowing Cl 2 gas at a flow rate of about 8 cc/min; and
flowing Ar gas at a flow rate of about 5 cc/min.