Method of fabricating vertical structure compound semiconductor devices

• US 7,384,807 B2
• Filed: 06/03/2004
• Issued: 06/10/2008
• Est. Priority Date: 06/04/2003
• Status: Expired due to Fees

• Current Assignee: Verticle, Inc.
• Original Assignee: Verticle, Inc.
• Inventors: Yoo, Myung Cheol
• Primary Examiner(s): Coleman; W. David
• Assistant Examiner(s): Kim; Su C.
• Application Number:
  US10/861,743
• Publication Number:
  US 20040245543A1
• Time in Patent Office: 1,468 Days
• Field of Search: 438/22, 438/28, 438/29, 438/69, 438/956, 257/13, 257/79, 257/88, 257/E33.054, 257/E25.028, 257/E25.032
• US Class Current: 438/29
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: Y10S 438/956 Making multiple wavelength emissive device

Abstract

A method of fabricating a vertical structure opto-electronic device includes fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate, and then removing the substrate using a laser lift-off process. The method then fabricates a metal support structure in place of the substrate. In one aspect, the step of fabricating a metal support structure in place of the substrate includes the step of plating the metal support structure using at least one of electroplating and electro-less plating. In one aspect, the vertical structure is a GaN-based vertical structure, the crystal substrate includes sapphire and the metal support structure includes copper. Advantages of the invention include fabricating vertical structure LEDs suitable for mass production with high reliability and high yield.

Claims

1. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate, wherein the fabricating the metal support structure in place of the crystal substrate including

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over the ITO layer,

plating a Cu layer over the Au buffer layer using at least one of electroplating and electro-less plating, wherein the vertical structure opto-electronic device is a GaN-based vertical structure, the crystal substrate includes sapphire and wherein the GaN-based vertical structure includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer, and

wherein trenches are formed from the-GaN buffer layer through the crystal substrate according to the following rules

a) trench dimension is substantially similar to a laser beam spot size to relieve shock wave during the laser lift-off process,

b) the trenches are narrower than about 100 microns wide and extend no deeper than about 3 microns into the crystal substrate, and

c) the trenches are formed using reactive ion etching.

2. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate, wherein the fabricating the metal support structure in place of the crystal substrate including

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over the ITO layer,

plating a Cu layer over the Au buffer layer using at least one of electroplating and electro-less plating, wherein the vertical structure opto-electronic device is a GaN-based vertical structure, the crystal substrate includes sapphire and wherein the GaN-based vertical structure includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer, and

wherein in order to relieve shock wave and easy de-lamination during a de-bonding process after the laser lift-off process, double coating for an adhesion bonding layer using polymer-base adhesives, the polymer-base adhesives including super glue and photo-exposable polymer between a GaN epi layer and a support wafer according to the following steps

a) a super glue layer is applied using spin coating,

b) the thickness of the super glue layer thickness is approximately 30 micron-thick,

c) the photo-exposable polymer is also applied using spin coating with thickness thicker than 20 microns,

d) the photo-exposable polymer is cured with an UV lamp, and

e) an UV lamp transparent sapphire support is used for curing the photo-exposable polymer.

3. A method of fabricating a vertical structure opto-electronic device, comprising

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate, wherein the fabricating the metal support structure in place of the crystal substrate including

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over ITO layer,

plating a Cu layer over the Au buffer layer using at least one of electroplating and electro-less plating, wherein the vertical structure opto-electronic device is a GaN-based vertical structure, the crystal substrate includes sapphire, and

using a diffuser plate made of materials transparent to a laser beam between the laser beam and the crystal substrate to obtain a uniform laser beam power distribution.

4. A method of fabricating a vertical structure opto-electronic device, comprising

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate, wherein the fabricating the metal support structure in place of the crystal substrate including

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over ITO layer,

plating a Cu layer over the Au buffer layer using at least one of electroplating and electro-less plating, wherein the vertical structure opto-electronic device is a GaN-based vertical structure, the crystal substrate includes sapphire, and

depositing a Cu alloy layer in order to gradually soften stress build up due to a thick metal layer, wherein the initial Cu alloy layer thickness is set up to ˜

10 μ

m, and wherein a plating rate is set up to 3˜

5 μ

m/hour.

5. The method of claim 4, further comprising the step of depositing a Cu layer in order to provide structural stiffness, wherein the plating rate of a Cu plating is up to 20 μ

m/hour, wherein for a Cu alloy plating, metal alloy plating solutions containing tin (Sn) and iron (Fe) are mixed with a Cu sulfate solution to improve mechanical strength and electrical conductivity of a Cu alloy support layer, wherein total thickness of the Cu alloy support layer is 70˜

90 μ

m, and wherein at the end of the Cu alloy plating, 0.5˜

1 μ

m-thick Au buffer layer is electroplated to protect Cu alloy layers from oxidation.

6. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu and w % herein the GaN-based vertical structure opto-electronic device includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer, and

wherein trenches are formed from the GaN buffer layer through the crystal substrate according to the following rules

a) trench dimension is substantially similar to a laser beam spot size, to relieve shock wave during the laser lift-off process,

b) the trenches are narrower than about 100 microns wide and extend no deeper than about 3 microns into the crystal substrate, and

c) the trenches are formed using reactive ion etching.

7. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu and wherein the GaN-based vertical structure opto-electronic device includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer, and

wherein in order to relieve shock wave and easy de-lamination during a de-bonding process after the laser lift-off process, double coating for an adhesion bonding layer using polymer-base adhesives, the polymer-base adhesives including super glue and the photo-exposable polymer between a GaN epi layer and a support wafer according to the following steps

a) a super glue layer is applied using spin coating,

b) a thickness of the super glue layer is approximately 30-micron thick,

c) the photo-exposable polymer is also applied using spin coating with thickness thicker than 20 microns,

d) the photo-exposable polymer is cured with an UV lamp, and

e) an UV lamp transparent sapphire support is used for curing the photo-exposable polymer.

8. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process;

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu and wherein the GaN-based vertical structure opto-electronic device includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer; and

using a diffuser plate made of materials transparent to a laser beam between the laser beam and the crystal substrate to obtain a uniform laser beam power distribution.

9. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu and wherein the GaN-based vertical structure opto-electronic device includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer; and

depositing a Cu alloy layer in order to gradually soften stress build up due to a thick metal layer, wherein the initial Cu alloy layer thickness is set up to ˜

10 μ

m, and wherein a plating rate is set up to 3˜

5 μ

m/hour.

10. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu and wherein the GaN-based vertical structure opto-electronic device includes a buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer; and

depositing a Cu layer in order to provide structural stiffness, wherein a plating rate of Cu plating is up to 20 μ

n/hour, wherein for a Cu alloy plating, metal alloy plating solutions containing tin (Sn) and iron (Fe) are mixed with a Cu sulfate solution to improve mechanical strength and electrical conductivity of a Cu alloy support layer, wherein the total thickness of the Cu alloy support layer is 70˜

90 μ

m, and wherein at the end of the Cu alloy plating, 0.5˜

1 μ

m-thick Au buffer layer is electroplated to protect the Cu alloy support layers from oxidation.

11. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate;

wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure includes Cu;

wherein the removing the crystal substrate comprises disposing a diffuser plate made of materials transparent to a laser beam between the laser beam and the crystal substrate to obtain uniform laser beam power distribution.

12. The method of claim 11, wherein the fabricating the metal support structure in place of the crystal substrate includes a step of plating the metal support structure using at least one of electroplating and electro-less plating.

13. The method of claim 11, further comprising:

fabricating a buffer layer between the plurality of vertical structure opto-electronic devices and the metal support structure.

14. The method of claim 11, wherein the fabricating the metal support structure in place of the crystal substrate includes

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over the ITO layer, and

plating a Cu layer over the Au buffer layer using at least one of electroplating and electro-less plating.

15. The method of claim 11, wherein the GaN-based vertical structure opto-electronic device includes the buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer.

16. The method of claim 15, wherein trenches are formed from the GaN buffer layer through the crystal substrate according to the following rules

a) trench dimension is substantially similar to the laser beam spot size to relieve shock wave during the laser lift-off process,

b) the trenches are narrower than about 100 microns wide and extend no deeper than about 3 microns into the crystal substrate, and

c) the trenches are formed using reactive ion etching, preferably inductively coupled plasma reactive ion etching (ICP RIE).

17. The method of claim 15, wherein in order to relieve shock wave and easy de-lamination during a de-bonding process after the laser lift-off process, double coating for an adhesion bonding layer using polymer-base adhesives, the polymer-base adhesives including super glue and photo-exposable polymer between a GaN epi layer and a support wafer according to the following steps

a) a super glue layer is applied using spin coating,

b) a thickness of the super glue layer is approximately 30-micron thick,

c) the photo-exposable polymer is also applied using spin coating with thickness thicker than 20 microns,

d) the photo-exposable polymer is cured with an UV lamp, and

e) an UV lamp transparent sapphire support is used for curing the photo-exposable polymer.

18. The method of claim 11, further comprising the step of performing ICP RIE etching and polishing on a lifted GaN wafer, wherein the ICP RIE etching and polishing exposes and produces an atomically flat surface of pure n-GaN, and wherein the atomically flat surface of pure n-GaN is particularly beneficial in producing high reflectivity from a reflective structure to be subsequently deposited.

19. The method of claim 11, further comprising the step of depositing a transparent conductive reflective layer using electron beam evaporation on the bottom of the metal support structure, wherein ITO (Indium Tin Oxide) is preferably used for the n-contact is reflector.

20. The method of claim 11, further comprising the step of depositing a Cu alloy layer in order to gradually soften stress build up due to a thick metal

layer, wherein the initial Cu alloy layer thickness is set up to ˜

10 μ

m, and wherein a plating rate is set up to 3˜

5 μ

m/hour.

21. The method of claim 20, further comprising the step of depositing a Cu layer in order to provide structural stiffness, wherein the plating rate of a Cu plating is up to 20 μ

m/hour, wherein for a Cu alloy plating, metal alloy plating solutions containing tin (Sn) and iron (Fe) are mixed with a Cu sulfate solution to improve mechanical strength and electrical conductivity of a Cu alloy support layer, wherein the total thickness of the Cu alloy support layer is 70˜

90 μ

m, and wherein at the end of the Cu alloy plating, 0.5˜

1 μ

m-thick Au buffer layer is electroplated to protect the Cu alloy support layers from oxidation.

22. The method of claim 11, further comprising the step of dicing individual devices by chemical or laser scribing.

23. A method of fabricating a vertical structure opto-electronic device, comprising:

fabricating a plurality of vertical structure opto-electronic devices on a crystal substrate;

removing the crystal substrate using a laser lift-off process; and

fabricating a metal support structure in place of the crystal substrate, wherein the vertical structure opto-electronic device is a GaN-based vertical structure opto-electronic device, the crystal substrate includes sapphire and the metal support structure is formed by depositing a Cu alloy layer in order to gradually soften stress build up due to a thick metal layer, wherein the initial Cu alloy layer thickness is set up to ˜

1˜

10 μ

m, and wherein a plating rate is set up to 3˜

5 μ

m/hour.

24. The method of claim 23, wherein the fabricating the metal support structure in place of the crystal substrate uses at least one of electroplating and electro-less plating.

25. The method of claim 23, further comprising:

fabricating a buffer layer between the plurality of vertical structure opto-electronic devices and the metal support structure.

26. The method of claim 23, wherein the fabricating the metal a support structure in place of the crystal substrate includes

depositing an ITO (Indium Tin Oxide) layer forming an n-contact,

depositing an Au buffer layer over the ITO layer, and

plating the Cu alloy layer over the Au buffer layer using at least one of electroplating and electro-less plating.

27. The method of claim 23, wherein the GaN-based vertical structure opto-electronic device includes the buffer layer comprising an AlGaN buffer layer in addition to a GaN buffer layer or a AlN buffer layer to provide a thermal diffusion barrier to protect a polymer-base adhesive layer.

28. The method of claim 27, wherein trenches are formed from the GaN buffer layer through the crystal substrate according to the following rules

a) trench dimension is substantially similar to a laser beam spot size to relieve shock wave during the laser lift-off process,

b) the trenches are narrower than about 100 microns wide and extend no deeper than about 3 microns into the crystal substrate, and

c) the trenches are formed using reactive ion etching, preferably inductively coupled plasma reactive ion etching (ICP RIE).

29. The method of claim 27, wherein in order to relieve shock wave and easy de-lamination during a de-bonding process after the laser lift-off process, double coating for an adhesion bonding layer using polymer-base adhesives, the polymer-base adhesives including super glue and photo-exposable polymer between a GaN epi layer and a support wafer according to the following steps

a) a super glue layer is applied using spin coating,

b) a thickness of the super glue layer is approximately 30-micron thick,

c) the photo-exposable polymer is also applied using spin coating with thickness thicker than 20 microns,

d) the photo-exposable polymer is cured with an UV lamp, and

e) an UV lamp transparent sapphire support is used for curing the photo-exposable polymer.

30. The method of claim 23, further comprising using a diffuser plate made of materials transparent to a laser beam between the laser beam and the crystal substrate to obtain uniform laser beam power distribution.

31. The method of claim 23, further comprising performing inductively coupled plasma reactive ion etching (ICP RIE) and polishing on a lifted GaN wafer, wherein the ICP RIE etching and polishing exposes and produces an atomically flat surface of pure n-GaN, and wherein the atomically flat surface of pure n-GaN is particularly beneficial in producing high reflectivity from a reflective structure to be subsequently deposited.

32. The method of claim 23, further comprising depositing a transparent conductive reflective layer using an electron beam evaporation on the bottom of the metal support structure, wherein ITO (Indium Tin Oxide) is preferably used for the n-contact is reflector.

33. The method of claim 23, further comprising depositing a Cu layer in order to provide structural stiffness, wherein the plating rate of Cu plating is up to 20 μ

m/hour, wherein for a Cu alloy plating, metal alloy plating solutions containing tin (Sn) and iron (Fe) are mixed with a Cu sulfate solution to improve mechanical strength and electrical conductivity of a Cu alloy support layer, wherein the total thickness of the Cu alloy support layer is 70˜

90 μ

m, and wherein at the end of the Cu alloy plating, 0.5˜

1 μ

m-thick Au buffer layer is electroplated to protect the Cu alloy support layers from oxidation.

34. The method of claim 23, further comprising dicing individual devices by chemical or laser scribing.