Laser lift-off on isolated III-nitride light islands for inter-substrate LED transfer
A laser liftoff process is provided. A device layer can be provided on a transfer substrate. Channels can be formed through the device layer such that devices comprising remaining portions of the device layer are laterally isolated from one another by the channels. The transfer substrate can be bonded to a target substrate through an adhesion layer. Surface portions of the devices can be removed from an interface region between the transfer substrate and the devices by irradiating a laser beam through the transfer substrate onto the devices. The laser irradiation decomposes the III-V compound semiconductor material. The channels provide escape paths for the gaseous products (such as nitrogen gas) that are generated by the laser irradiation. The transfer substrate is separated from a bonded assembly including the target substrate and remaining portions of the devices. The devices can include a III-V compound semiconductor material.
1. A method of transferring devices comprising, comprising:
providing a combination of a transfer substrate and a device layer thereupon;
forming a first adhesion layer on the device layer;
forming channels through the device layer, wherein devices comprising remaining portions of the device layer are laterally isolated from one another by the channels;
forming a second adhesion layer on a target substrate;
bonding the devices on the transfer substrate to the target substrate through an adhesion layer by forming the adhesion layer by bonding the first adhesion layer and the second adhesion layer;
removing surface portions of the devices from an interface region between the transfer substrate and the devices by irradiating a laser beam through the transfer substrate onto the devices; and
separating the transfer substrate from a bonded assembly including the target substrate and remaining portions of the devices.
2. The method of claim 1 , wherein the device layer comprises a III-V compound semiconductor material.
3. The method of claim 2 , wherein the III-V compound semiconductor material is a III-N compound semiconductor material.
4. The method of claim 3 , wherein:
portions of the III-N compound semiconductor material at the surface portions of the devices are decomposed into nitrogen gas and Group III metal portions by irradiation of the laser beam; and
the nitrogen gas escapes to ambient through the channels.
5. The method of claim 4 , further comprising removing the Group III metal portions selective to remaining portions of the III-N compound semiconductor material.
6. The method of claim 1 , further comprising:
forming a photoresist layer over the device layer;
lithographically patterning the photoresist layer to form discrete remaining portions of the photoresist layer over the device layer; and
transferring a pattern in the photoresist layer through the device layer by performing an etch process that employs the patterned photoresist layer as an etch mask.
7. The method of claim 1 , wherein the devices comprise at least one light emitting device.
8. The method of claim 1 , wherein the bonded assembly comprises a direct view display panel containing red, green, and blue wavelength light emitting diodes and sensors bonded to the target substrate.
9. The method of claim 2 , wherein:
the transfer substrate comprises aluminum oxide;
the III-V compound semiconductor material comprises a material selected from GaN, AlGaN and GaInN; and
the devices comprise light emitting diodes.
10. The method of claim 1 , wherein:
the devices comprise a rectangular array of light emitting devices; and
the channels form a rectangular grid by which the light emitting devices in the rectangular array are laterally spaced from one another.
11. The method of claim 10 , wherein the channels have a width in a range from 13 nm to 1 micron.
12. The method of claim 10 , wherein the laser beam radiation has a peak wavelength at which the transfer substrate is transparent to the radiation, and at which a III-V compound semiconductor material in the device layer absorbs the laser beam radiation.
13. The method of claim 1 , wherein the transfer substrate is an initial growth substrate on which the device layer is formed by deposition of at least one layer including a III-V compound semiconductor material.
14. The method of claim 1 , wherein:
the device layer comprises a plurality of types of light emitting devices; and
each of the devices is laterally surrounded by channels and comprises a combination of light emitting devices that emit light at different wavelengths.