Selective transfer of micro devices
What is disclosed is a method of selectively transferring micro devices from a donor substrate to contact pads on a receiver substrate. Micro devices being attached to a donor substrate with a donor force. The donor substrate and receiver substrate are aligned and brought together so that selected micro devices meet corresponding contact pads. A receiver force is generated to hold selected micro devices to the contact pads on the receiver substrate. The donor force is weakened and the substrates are moved apart leaving selected micro devices on the receiver substrate. Several methods of generating the receiver force are disclosed, including adhesive, mechanical and electrostatic techniques.
1 . A method of transferring micro devices, the method comprising:
positioning a donor substrate proximal to a receiver substrate, the donor substrate including the micro devices and the receiver substrate including a bonding layer for creating an electrostatic transfer force for transferring selected micro devices;
applying a current to the bonding layer to physically morph the bonding layer and create the electrostatic force on the selected micro devices; and
reducing effect of said electrostatic transfer force on unwanted micro devices, the micro devices including the selected micro devices and the unwanted micro devices.
2 . A method of transferring micro devices, comprising:
positioning a donor substrate comprising micro devices proximal to a receiver substrate, wherein the receiver substrate comprises a current curable bonding layer; and
transferring at least one of the micro devices from the donor substrate to the receiver substrate by applying a current to the current curable bonding layer proximal to the at least one of the micro devices.
3 . The method of claim 2 , wherein the current is applied using a circuitry located on the receiver substrate.
4 . The method of claim 2 , wherein the current is supplied by circuitry integrated in the receiver substrate that is partially or fully shared with circuitry that drives the micro devices in an operational mode.
5 . The method of claim 2 , wherein the current curable bonding layer comprises one or more contact pads and applying current to the current curable bonding layer comprises curing a portion of the current curable bonding layer between the one or more contact pads.
6 . The method of claim 2 , wherein the current curable bonding layer comprises an adhesive including conductive nanoparticles that, passing the current through the current curable bonding layer fuses the conductive nanoparticles together to decrease resistance and transform the current curable bonding layer from non-conductive to conductive.
7 . The method of claim 2 , wherein the current for curing the current curable bonding layer flows through a first micro device of the micro devices and the current curable bonding layer to a contact pad on the receiver substrate to effect vertical current curing.
8 . The method of claim 2 , wherein contact pads including two electrically isolated conductive elements are coupled to the current curable bonding layer, and wherein the applied current flows between the two electrically isolated conductive elements through the current curable bonding layer to effect lateral current curing.
9 . The method of claim 2 , wherein the current curable bonding layer is applied selectively to a subset of contact pads on the receiver substrate to enable selective bonding of corresponding micro devices.
10 . The method of claim 2 , wherein the current curable bonding layer functions as a dielectric to enable electrostatic attraction during transfer of the at least one of the micro devices, and after curing by current, provides a conductive interlayer that electrically couples electrodes of the at least one of the micro devices to the receiver substrate.