Through backplane laser irradiation for die transfer
Light emitting devices can be disposed on the front side of a transparent backplane. A laser beam can be irradiated through the transparent backplane and onto a component located on the front side of the transparent backplane. In one embodiment, the component may be a solder material portion that is reflowed to bond the light emitting devices to the transparent backplane. In another embodiment, the component may be a solder material bonded to a defective bonded light emitting device. In this case, the laser irradiation can reflow the solder material to dissociate the defective bonded light emitting device from the transparent backplane. In yet another embodiment, the component may be a device component that is electrically modified by the laser irradiation.
1. A method of manufacturing an assembly of a backplane and light emitting devices, the method comprising:
providing a substrate with dies of light emitting devices thereupon, wherein a device-side bonding pad is provided on each of the light emitting devices;
bonding at least one of the light emitting devices to the backplane without bonding at least another of the light emitting devices to the backplane;
dissociating the at least one bonded light emitting device from the substrate by irradiating a laser beam through the substrate and onto each region of the substrate in contact with the at least one bonded light emitting device while the at least another of the light emitting devices remains attached to the substrate and not bonded to the backplane; and
separating the substrate and the at least another of the light emitting devices from an assembly of the backplane and the at least one bonded light emitting device that is bonded to the backplane;
wherein the backplane comprises a metal interconnect layer including a plurality of metal interconnect structures embedded in at least one insulating material and providing electrical connections between the light emitting devices on the backplane and input/output pins of the backplane.
2. The method of claim 1 , wherein bonding of the at least one light emitting devices to the backplane is performed by irradiating another laser beam through the backplane.
3. The method of claim 1 , wherein the laser beam ablates each region of the substrate in contact with the at least one bonded light emitting device.
4. The method of claim 1 , wherein:
the substrate comprises sapphire; and
each region of the substrate in contact with the at least one bonded light emitting device prior to application the laser beam comprises a compound semiconductor material.
5. The method of claim 1 , wherein each of the light emitting devices comprises a vertical stack of a multi-quantum-well; a p-doped III-V compound semiconductor layer, and a transparent conductive oxide layer.
6. The method of claim 1 , wherein:
the laser beam has an ultraviolet wavelength; and
the backplane comprises a polymeric plastic material that is transparent at the ultraviolet wavelength of the laser beam.
7. A method of manufacturing an assembly of a backplane and light emitting devices, the method comprising:
providing a substrate with dies of light emitting devices thereupon, forming device-side bonding pads on the dies of light emitting devices, such that the device-side bonding pad is provided on each of the light emitting devices;
forming backplane-side bonding pads on the backplane; disposing solder material portions between facing pairs of a device-side bonding pad among the device-side bonding pads and a backplane-side bonding pad among the backplane-side bonding pads;
bonding at least one of the light emitting devices to the backplane by irradiating a heating laser beam through the backplane, wherein a first subset of the solder material portions is irradiated by the heating laser beam and a second subset of the solder material portions is not irradiated by the heating laser beam; and
dissociating each of the at least one bonded light emitting device from the substrate by irradiating an ablation laser beam through the substrate and onto each region of the substrate in contact with the at least one bonded light emitting device.
8. The method of claim 7 , wherein:
the ablation laser beam has a shorter wavelength than the heating laser beam; and
the light emitting devices comprise vertical light emitting diodes in which the p-side and n-side contacts are located on opposite sides of the light emitting diode.
9. The method of claim 8 , wherein the ablation laser beam comprises an ultraviolet laser beam and the heating laser beam comprises an infrared laser beam.
10. The method of claim 7 , further comprising:
forming a device-side solder material portion on each of the device-side bonding pads;
and forming a backplane-side solder material portion on each of the backplane-side bonding pads, wherein a combination of a device-side solder material portion and a backplane-side solder material portion is provided between each facing pair of a device-side bonding pad and a backplane-side bonding pad.
11. The method of claim 10 , wherein the heating laser beam reflows a respective pair of a device-side solder material portion and a backplane-side solder material portion by irradiating the heating laser beam through the backplane.
12. The method of claim 1 , wherein:
the light emitting devices comprise vertical light emitting diodes in which the p-side and n-side contacts are located on opposite sides of the light emitting diode;
the substrate comprises a stack of a transparent material layer and an undoped III-V compound material layer; and
the laser beam passes through the transparent material layer and ablates an irradiated portion of the undoped III-V compound material layer.
13. The method of claim 1 , wherein:
the dies of light emitting devices are provided as a two-dimensional periodic array having a first pitch along a first direction and having a second pitch along a second direction; and
upon separation of the first assembly and the second assembly, every other die of light emitting devices along the first horizontal direction is transferred from the substrate to the second assembly and every other die of light emitting devices along the second horizontal direction is transferred from the substrate to the second assembly.
14. The method of claim 13 , wherein the backplane has a unit conductive bond pad pattern that is repeated in a two-dimensional array, the unit conductive bond pad pattern including a plurality of bond pads having a periodicity along one horizontal direction that is equal to twice the first pitch and having a periodicity along another horizontal direction that is equal to twice the second pitch.