SELECTIVE MICRO DEVICE TRANSFER TO RECEIVER SUBSTRATE
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 selected micro devices in an array of micro devices each of which is bonded to a donor substrate with a donor force to contact pads in an array on a receiver substrate, the method comprising:
aligning the donor substrate and the receiver substrate so that each of the selected micro devices is in line with a contact pad on the receiver substrate;
moving the donor substrate and the receiver substrate together until each of the selected micro devices is in contact or proximity with a respective contact pad on the receiver substrate;
generating a receiver force that acts to hold the selected micro devices to their contact pads; and
moving the donor substrate and the receiver substrate apart leaving the selected micro devices on the receiver substrate.
2 . The method of claim 1 further comprising weakening the donor force bonding the micro devices to the donor substrate to assist micro device transfer.
3 . The method of claim 2 wherein the donor force for the selected micro devices is weakened to improve selectivity in micro device transfer.
4 . The method of claim 1 wherein the receiver force is generated selectively to improve selectivity in micro device transfer.
5 . The method of claim 1 further comprising weakening the donor force using laser lift off.
6 . The method of claim 1 further comprising weakening the donor force by heating an area of the donor substrate.
7 . The method of claim 4 further comprising modulating the receiver force by heating the receiver substrate.
8 . The method of claim 7 wherein the heating is performed by passing a current through the contact pads.
9 . The method of claim 4 wherein the receiver force is generated by mechanical grip.
10 . The method of claim 1 further comprising performing an operation on the receiver substrate so that the contact pads permanently bond with the selected micro devices.
11 . The method of claim 4 wherein the receiver force is generated by electrostatic attraction between the selected micro devices and the receiver substrate.
12 . The method of claim 1 wherein the receiver force is generated by an adhesive layer positioned between the selected micro devices and the receiver substrate.
13 . The method of claim 1 further comprising:
removing the donor force; and
applying a push force to selected micro devices to move the devices toward the receiver substrate.
14 . The method of claim 13 wherein the push force is created by a sacrificial layer deposited between the selected micro device and the donor substrate.
15 . A receiver substrate structure comprising:
an array of landing areas for holding micro devices from a donor substrate selectively, each landing area comprising:
at least one contact pad for coupling a micro device to a circuit or a potential in the receiver substrate; and
at least one force modulation element for creating a receiver force for holding a micro devices on the receiver substrate.
16 . The receiver substrate structure of claim 15 wherein the force modulation element is an electrostatic structure.
17 . The receiver substrate structure of claim 15 wherein the force modulation element is a mechanical grip.
18 . The receiver substrate structure of claim 15 wherein for each landing area, a same element acts as the force modulation element and the contact pad.