Flip chip light emitting diode devices having thinned or removed substrates
View Patent ↗In a method for fabricating a flip-chip light emitting diode device, epitaxial layers ( 14, 114 ) are deposited on a growth substrate ( 16, 116 ) to produce an epitaxial wafer. A plurality of light emitting diode devices are fabricated on the epitaxial wafer. The epitaxial wafer is diced to generate a device die ( 10, 110 ). The device die ( 10, 110 ) is flip chip bonded to a mount ( 12, 112 ). The flip chip bonding includes securing the device die ( 10, 110 ) to the mount ( 12, 112 ) by bonding at least one electrode ( 20, 22, 120 ) of the device die ( 10, 110 ) to at least one bonding pad ( 26, 28, 126 ) of the mount ( 12, 112 ). Subsequent to the flip chip bonding, a thickness of the growth substrate ( 16, 116 ) of the device die ( 10, 110 ) is reduced.
1. A method for fabricating a flip-chip light emitting diode device, the method including:
depositing epitaxial layers on a growth substrate to produce an epitaxial wafer;
fabricating a plurality of light emitting diode devices on the epitaxial wafer;
dicing the epitaxial wafer to generate a device die;
flip chip bonding the device die to a mount, the flip chip bonding including securing the device die to the mount by bonding at least one electrode of the device die to at least one bonding pad of the mount; and
subsequent to the flip chip bonding, reducing a thickness of the growth substrate of the device die.
2. The method as set forth in claim 1 , wherein the reducing of a thickness of the growth substrate subsequent to the flip chip bonding includes:
thinning the growth substrate subsequent to the flip chip bonding.
3. The method as set forth in claim 1 , wherein the reducing of a thickness of the growth substrate subsequent to the flip chip bonding includes:
removing the growth substrate subsequent to the flip chip bonding.
4. The method as set forth in claim 1 , further including:
disposing an underfill material at least between the mount and the flip chip bonded device die.
5. The method as set forth in claim 4 , wherein the disposing of the underfill material includes: disposing the underfill material on the mount prior to the flip chip bonding.
6. The method as set forth in claim 4 , wherein the disposing of the underfill material includes:
disposing the underfill material after the flip chip bonding, the disposing of the underfill material further securing the device die to the mount.
7. The method as set forth in claim 4 , further including:
disposing a phosphor in the underfill material.
8. The method as set forth in claim 4 , wherein the underfill material is selected to have a thermal expansion coefficient matching one of a thermal expansion coefficient of the device die, a thermal expansion coefficient of the mount, and a thermal expansion coefficient value intermediate between the thermal expansion coefficients of the device die and the mount.
9. The method as set forth in claim 4 , wherein the disposing an underfill material includes:
disposing a fluid underfill material; and
curing the fluid underfill material.
10. The method as set forth in claim 1 , wherein the reducing of a thickness of the growth substrate includes:
mechanically grinding away at least a portion of the growth substrate.
11. The method as set forth in claim 1 , wherein the reducing of a thickness of the growth substrate includes:
chemically etching the growth substrate using a chemical etchant.
12. The method as set forth in claim 11 , wherein the chemical etching includes:
selecting a chemical etchant that etches the growth substrate preferentially over an etch stop epitaxial layer of the deposited epitaxial layers, whereby the chemical etching terminates substantially at the etch stop epitaxial layer.
13. The method as set forth in claim 11 , wherein the chemical etchant produces a substantially isotropic chemical etching that simultaneously removes material from a top and sides of the growth substrate.
14. The method as set forth in claim 13 , the method further including:
subsequent to the flip chip bonding and prior to the chemical etching, arranging an underfill material to encapsulate the epitaxial layers while leaving the top and sides of the growth substrate unencapsulated, the substantially isotropic chemical etching being ineffective for etching the encapsulating underfill material.
15. The method as set forth in claim 1 , wherein the reducing of a thickness of the growth substrate includes:
thinning or removing the growth substrate by laser ablation.
16. The method as set forth in claim 1 , wherein the epitaxial layers define a vertical cavity surface emitting laser diode.
17. The method as set forth in claim 1 , wherein the epitaxial layers include group III-nitride compound semiconductor layers.
18. The method as set forth in claim 17 , wherein the growth substrate is a silicon carbide substrate.
19. The method as set forth in claim 17 , wherein the growth substrate is a sapphire substrate, and the reducing of a thickness of the growth substrate includes removing the sapphire substrate.
20. The method as set forth in claim 19 , the method further including:
subsequent to the removing the growth substrate, forming a back-side electrode to an epitaxial layer exposed by the removing of the growth substrate.
21. A method for fabricating a flip-chip light emitting diode device, the method including:
depositing epitaxial layers on a growth substrate to produce an epitaxial wafer;
fabricating a plurality of light emitting diode devices on the epitaxial wafer;
dicing the epitaxial wafer to generate a device die;
flip chip bonding the device die to a mount, the flip chip bonding including securing the device die to the mount by bonding at least one electrode of the device die to at least one bonding pad of the mount;
subsequent to the flip chip bonding, reducing a thickness of the growth substrate of the device die by one of thinning and removing the growth substrate; and
subsequent to the thinning or removing of the growth substrate, forming a back-side electrode to one of the thinned growth substrate and an epitaxial layer exposed by the removing of the growth substrate.
22. The method as set forth in claim 21 , further including:
electrically connecting the back-side electrode to a wiring bonding pad of the mount.
23. The method as set forth in claim 21 , wherein the epitaxial layers include group III-nitride compound semiconductor layers, the growth substrate is a sapphire substrate, and the reciting of a thickness of the growth substrate by one of thinning and removing the growth substrate includes removing the sapphire substrate by application of a laser beam.
24. A method for improving light emission of a flip-chip bonded light emitting diode device that is flip chip bonded to a mount, the method including:
thinning or removing a growth substrate of the light emitting diode device, the growth substrate of the flip-chip bonded light emitting diode device being arranged distal from the mount, the thinning or removing being performed while epitaxial layers of the light emitting diode device are flip chip bonded to the mount, the flip chip bonding effecting a securing of the light emitting diode device to the mount during the thinning or removing.
25. The method as set forth in claim 24 , the method further including:
prior to the thinning or removing, disposing an adhesive underfill material between the mount and the light emitting diode device, the adhesive underfill material adhesively further securing the light emitting diode device to the mount during the thinning or removing.
26. The method as set forth in claim 25 , wherein the adhesive underfill material additionally protects the epitaxial layers of the light emitting diode device during the thinning or removing.