LED DEVICE WITH BRAGG REFLECTOR AND METHOD OF SINGULATING LED WAFER SUBSTRATES INTO DICE WITH SAME

• US 20150214439A1
• Filed: 01/26/2015
• Published: 07/30/2015
• Est. Priority Date: 01/27/2014
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Glo AB (Shoei Electronic Materials, Inc.)
• Inventors: Herner, Scott Brad
• Granted Patent: US 9,419,185 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/18 within the light emitting region
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A method of dicing semiconductor devices from a substrate includes forming a Bragg reflector over a bottom side of the substrate, where the bottom side is opposite of a top side, generating a pattern of defects in the substrate with a laser beam from the bottom side of the substrate, and applying pressure to the substrate to dice the substrate along the pattern of defects. The Bragg reflector includes a first layer of dielectric material having a first index of refraction and a second dielectric material having a second index of refraction different from the first index of refraction.

Claims

1. A method of dicing semiconductor devices from a substrate, comprising:

forming a Bragg reflector over a bottom side of the substrate, wherein the bottom side is opposite of a top side and the Bragg reflector comprises a first layer of dielectric material having a first index of refraction and a second dielectric material having a second index of refraction different from the first index of refraction;

generating a pattern of defects in the substrate with a laser beam from the bottom side of the substrate; and

applying pressure to the substrate to dice the substrate along the pattern of defects.

2. The method of claim 1, wherein generating the pattern of defects comprises generating the pattern of defects in the substrate with a laser beam through the Bragg reflector.

3. The method of claim 2, wherein the laser beam peak wavelength is transmitted through the first and second dielectric layers which are transparent to the laser beam peak wavelength.

4. The method of claim 1, further comprising selectively removing portions of the Bragg reflector to expose portions of the bottom side of the substrate.

5. The method of claim 4, wherein:

the step of selectively removing comprises etching grooves through the Bragg reflector to expose the bottom side of the substrate and to define a pattern of individual LED dies on the bottom side of the substrate; and

generating the pattern of defects comprises generating the pattern of defects in the substrate with a laser beam through the grooves.

6. The method claim 5, wherein the step of selectively removing portions of the Bragg reflector comprises selectively removing portions of the Bragg reflector using laser ablation.

7. The method of claim 5, wherein the step of selectively removing portions of the Bragg reflector comprises patterning a temporary mask over the Bragg reflector and wet or dry etching exposed portions of the Bragg reflector in the temporary mask.

8. The method of claim 7, wherein the Bragg reflector comprises a stack of TiO₂ and SiO₂ layers which are dry etched by chlorine gas.

9. The method of claim 5, wherein selectively removing portions of the Bragg reflector comprising selectively depositing the Bragg reflector through a shadow mask and removing the shadow mask to selectively remove portions of the Bragg reflector deposited on the mask.

10. The method of claim 1, further comprising forming a plurality of LED layers over the top side of the substrate, wherein the semiconductor devices comprise LED dice.

11. The method of claim 10, wherein the substrate comprises sapphire, the LED layers comprise III-nitride semiconductor layers, and the Bragg reflector comprises a stack of layers comprising at least two TiO₂, SiO₂, Si₃N₄, Ta₂O₅, HfO₂, Al₂O₃, ZrO₂ or ZnO.

12. The method of claim 11, wherein the LED layers comprise III-nitride nanowire based LED layers formed over GaN buffer layer located on the top side of the sapphire substrate, and the Bragg reflector comprises a stack of alternating layers of TiO₂ and SiO₂ deposited by evaporation, and the Bragg reflector has a thicknesses of t=λ

/4n, where λ

is the wavelength that is desired to be reflected and n is the index of refraction of material comprising the Bragg reflector.

13. A light emitting diode (LED) die comprising a substrate, a plurality of LED layers located over a top side of the substrate, and a Bragg reflector located over a bottom side of the substrate, wherein the Bragg reflector comprises a first layer of dielectric material having a first index of refraction and a second dielectric material having a second index of refraction different from the first index of refraction.

14. The die of claim 13, wherein the Bragg reflector reflects light from the LED layers back through the top side of the substrate.

15. The die of claim 13, wherein the Bragg reflector comprises a distributed Bragg reflector having 2 to 6 Bragg pairs of the first and the second layers of dielectric material.

16. The die of claim 13, wherein the substrate comprises sapphire, the LED layers comprise III-nitride semiconductor layers, and the Bragg reflector comprises a stack of layers comprising at least two TiO₂, SiO₂, Si₃N₄, Ta₂O₅, HfO₂, Al₂O₃, ZrO₂ or ZnO.

17. The die of claim 13, wherein the LED layers comprise III-nitride nanowire based LED layers.

18. The die of claim 17, wherein the LED layers are located over GaN buffer layer located on the top side of the sapphire substrate, and the Bragg reflector comprises a stack of alternating layers of TiO₂ and SiO₂ deposited by evaporation.

19. The die of claim 18, wherein the Bragg reflector has a thicknesses of t=λ

/4n, where λ

is the wavelength that is desired to be reflected and n is the index of refraction of material comprising the Bragg reflector.

20. The die of claim 13, wherein a band of laser created defects is located on a side surface of the LED die.