High surface quality GaN wafer and method of fabricating same

• US 20060029832A1
• Filed: 08/26/2005
• Published: 02/09/2006
• Est. Priority Date: 06/08/2001
• Status: Abandoned Application

• Current Assignee: Robert P. Vaudo, Xueping Xu
• Original Assignee: Robert P. Vaudo, Xueping Xu
• Inventors: Xu, Xueping, Vaudo, Robert P.
• Application Number:
  US11/213,535
• Publication Number:
  US 20060029832A1
• Time in Patent Office: Days
• US Class Current: 428/698
• CPC Class Codes: C09G 1/02 containing abrasives or grinding agents abrasives as such C09K3/14; polishing of semi-conductors H01L
• CPC Class Codes: C09K 3/1409 Abrasive particles per se preparation of diamond C01B32/25
• CPC Class Codes: C09K 3/1463 Aqueous liquid suspensions
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: H01L 21/02005 Preparing bulk and homogeneous wafers
• CPC Class Codes: H01L 21/02019 Chemical etching
• CPC Class Codes: H01L 21/02024 Mirror polishing
• CPC Class Codes: H01L 21/30617 Anisotropic liquid etching
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: Y10T 428/21 Circular sheet or circular blank

Abstract

Al_xGa_yIn_zN, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1, and x+y+z=1, characterized by a root mean square surface roughness of less than 1 nm in a 10×10 μm² area. The Al_xGa_yIn_zN may be in the form of a wafer, which is chemically mechanically polished (CMP) using a CMP slurry comprising abrasive particles, such as silica or alumina, and an acid or a base. High quality Al_xGa_yIn_zN wafers can be fabricated by steps including lapping, mechanical polishing, and reducing internal stress of said wafer by thermal annealing or chemical etching for further enhancement of its surface quality. CMP processing may be usefully employed to highlight crystal defects of an Al_xGa_yIn_zN wafer.

Claims

1. A wafer comprising Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

2. The wafer according to claim 1, wherein pits constituting said pit density are less than 0.4 μ

m in diameter.

3. The wafer of claim 1, wherein the RMS surface roughness of said wafer is less than 0.7 nm in a 10×

10 μ

m² area.

4. The wafer of claim 1, wherein the RMS surface roughness of said wafer is less than 0.5 nm in a 10×

10 m² area.

5. The wafer of claim 1, wherein the RMS surface roughness of said wafer is at least less than 0.4 nm in a 2×

2 μ

m² area.

6. The wafer of claim 1, wherein the RMS surface roughness of said wafer is less than 0.2 nm in a 2×

2 μ

m² area.

7. The wafer of claim 1, wherein the RMS surface roughness of said wafer is less than 0.15 nm in a 2×

2 m² area.

8. The wafer of claim 1, characterized by a step structure when observed with an atomic force microscope.

9. The wafer of claim 1, wherein the crystal defects are visible as small pits with diameters of less than 1 μ

m.

10. The wafer of claim 1, formed by chemically mechanically polishing (CMP) an Al_xGa_yIn_zN wafer blank, using a silica- or alumina-containing CMP slurry.

11. An epitaxial Al_xGa_yIn_zN crystal structure, comprising an epitaxial Al_xGa_yIn_zN thin film grown on a wafer comprising Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

12. The epitaxial Al_xGa_yIn_zN crystal structure of claim 11, comprising a wurtzite crystalline thin film.

13. The epitaxial Al_xGa_yIn_zN crystal structure of claim 11, where the epitaxial Al_x′

Ga_y′

In_z′

N thin film has the same composition as the wafer comprising Al_xGa_yIn_zN.

14. The epitaxial Al_xGa_yIn_zN crystal structure of claim 11, where the epitaxial Al_x′

Ga_y′

In_z′

N thin film has a different composition from the wafer comprising Al_xGa_yIn_zN.

15. The epitaxial Al_xGa_yIn_zN crystal structure of claim 11, where the epitaxial Al_x′

Ga_y′

In_z′

N thin film has a graded composition.

16. An optoelectronic device comprising at least one epitaxial Al_x′

Ga_y′

In_z′

N crystal structure grown on a wafer comprising Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

17. The optoelectronic device of claim 16, wherein the optoelectronic device is a light emitting diode.

18. The optoelectronic device of claim 16, wherein the optoelectronic device is a blue light laser diode.

19. The optoelectronic device of claim 16, wherein the optoelectronic device is incorporated into a light emitting diode.

20. The optoelectronic device of claim 16, wherein the optoelectronic device is incorporated into a magneto-optic memory device.

21. The optoelectronic device of claim 16, wherein the optoelectronic device is incorporated into a full color light emitting display.

22. The optoelectronic device of claim 16, wherein the optoelectronic device is incorporated into a DVD device.

23. A microelectronic device comprising at least one epitaxial Al_x′

Ga_y′

In_z′

N crystal structure grown on a wafer comprising Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

24. An epitaxial Al_x′

Ga_y′

In_z′

N crystal boule grown on a wafer comprising Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

25. Al_xGa_yIn_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1, having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².

26. GaN, having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×

10 μ

m² area and having a pit density of about 10⁶ to about 10⁷ pits/cm².