Method for quantification of extended defects in gallium-containing nitride crystals

• US 9,275,912 B1
• Filed: 08/29/2013
• Issued: 03/01/2016
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: SL Technology Incorporated (Reliv' International, Inc.)
• Original Assignee: Soraa, Inc.
• Inventors: Jiang, Wenkan, Ehrentraut, Dirk, Downey, Bradley C., D'Evelyn, Mark P.
• Primary Examiner(s): Perkins, Pamela E
• Application Number:
  US14/013,753
• Time in Patent Office: 915 Days
• Field of Search: 438/488, 438/705, 428/220
• US Class Current: 1/1
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/24 Optical enhancement of defects or not directly visible states, e.g. selective electrolytic deposition, bubbles in liquids, light emission, colour change voltage contrast G01R31/311

Abstract

Methods for quantifying extended defects in a gallium-containing nitride crystal, wafer, or device, are disclosed. The methods include providing a gallium-containing nitride crystal, wafer, or device, processing the gallium-containing nitride crystal, wafer, or device in an etchant solution comprising one or more of H₃PO₄, H₃PO₄ that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H₂SO₄; removing the gallium-containing nitride crystal, wafer, or device from the etchant solution; and quantifying the concentration of at least one of etch pits or etch grooves.

Claims

1. A method for quantifying extended defects in a gallium-containing nitride crystal, wafer, or device, comprising:

providing a gallium-containing nitride crystal, wafer, or device, wherein the crystal, wafer, or device comprises gallium and nitrogen, has a wurtzite crystal structure, and comprises a first surface having a crystallographic orientation that is miscut from a {10-10} m-plane by between about 0.01 degrees and about 60 degrees toward a [000-1] −

c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction;

preparing an etchant composition;

processing the gallium-containing nitride crystal, wafer, or device in the etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers;

removing the gallium-containing nitride crystal, wafer, or device from the etchant composition; and

quantifying a concentration of at least one of etch pits and etch grooves,

wherein quantifying the concentration of etch pits is performed by counting a number of the etch pits within a field of view; and

quantifying the concentration of etch grooves is performed by calculating a total length of the etch grooves within a field of view.

2. The method of claim 1, wherein the etchant composition comprises one or more of NaOH and KOH.

3. The method of claim 1, wherein the etchant composition comprises a solution of one or more of H₃PO₄, H₃PO₄ that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H₂SO₄.

4. The method of claim 3, wherein the etchant composition is prepared by conditioning of reagent-grade phosphoric acid to form polyphosphoric acid.

5. The method of claim 1, wherein the first surface has been prepared by chemical-mechanical polishing prior to performing the etch treatment.

6. The method of claim 1, further comprising protecting one or more surfaces of the gallium-containing nitride crystal using one or more of an etch-resistant tape, clamping an end or face of a crystal against an etch-resistant material, and coating with a paint comprising an etch-resistant material.

7. The method of claim 1, further comprising preparing a second surface that is substantially parallel to the first surface, wherein both the first surface and the second surface are chemical-mechanically polished, and processing both the first surface and the second surface in the etchant composition simultaneously.

8. The method of claim 1, wherein the gallium-containing nitride crystal, wafer, or device has been grown in an m-direction, the first surface is miscut from a {10-10} m-plane by between about 1 degree and about 5 degrees toward a [000-1] −

c-direction and by up to about 5 degrees toward an orthogonal <

1-210>

a-direction, and the concentration of at least one of threading dislocations and stacking faults is determined as a function of distance from the m-plane growth surface.

9. The method of claim 1, wherein the first surface has a crystallographic orientation that is miscut from a {10-10} m-plane by between about 0.05 degree and about 60 degrees toward a [000-1] −

c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction.

10. A method for quantifying extended defects in a gallium-containing nitride crystal, wafer, or device, comprising:

providing a gallium-containing nitride crystal, wafer, or device, wherein the crystal, wafer, or device comprises gallium and nitrogen, has a wurtzite crystal structure, and comprises a surface having a crystallographic orientation within 5 degrees of a (0001) +c-plane;

preparing a first etchant composition;

processing the gallium-containing nitride crystal, wafer, or device in the first etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 30 seconds and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers;

removing the gallium-containing nitride crystal, wafer, or device from the first etchant composition;

quantifying a concentration of at least one of etch pits and etch grooves on a (0001) +c-plane surface;

preparing a vicinal m-plane surface on the gallium-containing nitride crystal, wafer, or device, the vicinal m-plane surface having a crystallographic orientation that is miscut from a {10-10} m-plane by between about 0.01 degree and about 5 degrees toward a [000-1] −

c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction;

preparing a second etchant composition;

processing the gallium-containing nitride crystal gallium-containing nitride crystal, wafer, or device in the second etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers on the vicinal m-plane surface;

removing the gallium-containing nitride crystal gallium-containing nitride crystal, wafer, or device from the second etchant composition; and

quantifying a concentration of at least one of etch pits and etch grooves on the vicinal m-plane surface,

wherein quantifying the concentration of etch pits is performed by counting a number of the etch pits within a field of view; and

quantifying the concentration of etch grooves is performed by calculating a total length of the etch grooves within the field of view.

11. The method of claim 10, wherein the first etchant composition comprises one or more of NaOH and KOH and the gallium-containing nitride crystal, wafer, or device is processed in the first etchant composition at a temperature between about 170 degrees Celsius and about 500 degrees Celsius for a time between about five minutes and about five hours.

12. The method of claim 10, wherein the second etchant composition is a solution comprising one or more of H₃PO₄, H₃PO₄ that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H₂SO₄.

13. The method of claim 12, wherein the second etchant composition is prepared by conditioning of reagent-grade phosphoric acid to form polyphosphoric acid, increasing its boiling point.

14. The method of claim 10, wherein the vicinal m-plane surface has been prepared by chemical-mechanical polishing prior to performing the etch treatment.

15. The method of claim 10, further comprising protecting one or more surfaces of the gallium-containing nitride crystal using one or more of an etch-resistant tape, clamping an end or face of a crystal against an etch-resistant material, and coating with a paint comprising an etch-resistant material.

16. A method for quantifying extended defects in a gallium-containing nitride crystal, wafer, or device, comprising:

providing a gallium-containing nitride crystal, wafer, or device, wherein the crystal, wafer, or device comprises gallium and nitrogen, has a wurtzite crystal structure, and comprises a surface having a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

1 degree and about +60 degrees toward a [000-1] −

c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction;

preparing an etchant composition;

the etchant composition comprising a solution prepared by conditioning of reagent-grade phosphoric acid to form polyphosphoric acid, increasing its boiling point;

processing the gallium-containing nitride crystal, wafer, or device in the etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers;

removing the gallium-containing nitride crystal, wafer, or device from the etchant composition; and

quantifying a concentration of at least one of etch pits and etch grooves,

wherein quantifying the concentration of etch pits is performed by counting a number of the etch pits within a field of view; and

quantifying the concentration of etch grooves is performed by calculating a total length of the etch grooves within the field of view.

17. The method of claim 16, further comprising protecting one or more surfaces of the gallium-containing nitride crystal using one or more of an etch-resistant tape, clamping an end or face of a crystal against an etch-resistant material, and coating with a paint comprising an etch-resistant material.

18. The method of claim 16, wherein the surface having a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

1 degree and about +60 degrees toward a [000-1] −

c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction has been prepared by chemical-mechanical polishing prior to performing etch treatment.

19. A method for quantifying extended defects in a gallium-containing nitride crystal, wafer, or device, comprising:

providing a gallium-containing nitride crystal, wafer, or device, wherein the crystal, wafer, or device comprises gallium and nitrogen, has a wurtzite crystal structure, and comprises a surface having a crystallographic orientation within 5 degrees of a (0001) +c-plane;

preparing a first etchant composition;

processing the gallium-containing nitride crystal, wafer, or device in the first etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers;

removing the gallium-containing nitride crystal, wafer, or device from the first etchant composition;

quantifying a concentration of at least one of etch pits and etch grooves on a (0001) +c-plane surface;

preparing a vicinal m-plane surface on the gallium-containing nitride crystal, wafer, or device, the vicinal m-plane surface having a crystallographic orientation that is miscut from a {10-10} m-plane by between about 0.05 degree and about 5 degrees toward a [000-1] −

c-direction and by up to about 5 degrees toward an orthogonal <

1-210>

a-direction;

preparing a second etchant composition;

processing the gallium-containing nitride crystal gallium-containing nitride crystal, wafer, or device in the second etchant composition at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours, wherein the processing temperature and time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers on the vicinal m-plane surface;

removing the gallium-containing nitride crystal gallium-containing nitride crystal, wafer, or device from the second etchant composition; and

quantifying the concentrations of at least one of etch pits and etch grooves on the vicinal m-plane surface,

wherein quantifying the concentration of etch pits is performed by counting a number of the etch pits within a field of view; and

quantifying the concentration of etch grooves is performed by calculating a total length of the etch grooves within the field of view.

20. The method of claim 19, wherein the vicinal m-plane surface has been prepared by chemical-mechanical polishing prior to performing the etch treatment.