Systems and methods for preparing GaN and related materials for micro assembly
View Patent ↗The disclosed technology relates generally to a method and system for micro assembling GaN materials and devices to form displays and lighting components that use arrays of small LEDs and high-power, high-voltage, and or high frequency transistors and diodes. GaN materials and devices can be formed from epitaxy on sapphire, silicon carbide, gallium nitride, aluminum nitride, or silicon substrates. The disclosed technology provides systems and methods for preparing GaN materials and devices at least partially formed on several of those native substrates for micro assembly.
1. A method of preparing printable materials for micro assembly from a native device substrate using an intermediate substrate having a controlled tackiness, the method comprising:
depositing one or more materials on the native device substrate, thereby forming an epitaxial material;
forming devices with the epitaxial material on the native device substrate;
forming electrically conductive protrusions on each of the devices;
delineating releasable structures comprising the devices in the epitaxial material, thereby partially exposing the device substrate;
forming anchoring structures and tethering structures such that the releasable structures are connected to the substrate by the anchoring structures and tethering structures;
temporarily bonding the devices to the intermediate substrate and performing a laser-lift off process, thereby separating the devices from the native device substrate and thereby inverting the devices for micro assembly, wherein:
the controlled tackiness of the intermediate substrate is configured so that a transfer element can remove the materials from the intermediate substrate for micro assembly, and
the native substrate is transparent to laser illumination that is absorbed strongly by an absorbing layer on the native substrate so that upon exposure to the laser illumination the absorbing layer at least partially decomposes or otherwise forms an interface that can initiate separation between the native substrate and the devices for micro assembly;
at least partially completing the formation or delineation of devices on the intermediate substrate;
releasing the devices from the intermediate substrate by removal of at least a portion of a selectively removable layer positioned between at least a portion of the intermediate substrate and at least a portion of the devices, thereby forming printable micro assemble-able devices from the native substrate via the intermediate substrate; and
transferring the released materials for micro assembly on the intermediate substrate to the transfer element, thereby presenting the devices for micro assembly in an inverted configuration, the transfer element also having controlled tackiness such that the transfer element can remove the devices for micro assembly from the intermediate substrate; and
micro assembling the devices onto a destination substrate using the transfer element.
2. The method of claim 1 , wherein the intermediate substrate comprises a stamp.
3. The method of claim 1 , wherein the intermediate substrate comprises a conformable elastomer having controlled tackiness.
4. The method of claim 1 , wherein the anchoring structures and tethering structures are formed in the epitaxial material.
5. The method of claim 1 , wherein the anchoring and tethering structures are formed from non-epitaxial material.
6. The method of claim 1 , wherein the transfer element comprises an elastomer stamp.
7. The method of claim 1 , comprising performing thermal treatment to temporarily bond the devices to the intermediate substrate to form a bonded pair of substrates.
8. The method of claim 1 , wherein the tackiness of the intermediate substrate is controlled by pressure or temperature.
9. The method of claim 1 , wherein the tackiness of the intermediate substrate is formed by temporary collapse of topographical features or viscoelastic rate-dependent adhesion effects, thereby forming a transient tackiness.