Researchers from Huazhong University of Science and Technology have reported a self-aligned laser transfer (SALT) based on directional photothermal regulation strategies that enables high-precision, programmable transfer of microchips or microLEDs without the need of precise laser-to-die alignment.
The researchers demonstrated multiple transfer printings of RGB MicroLED chips from different donor wafers highlight SALT’s self-aligned and batch-selective capabilities, which are crucial for efficient full-color MicroLED display assembly.
The key innovation lies in the introduction of a thermal conductivity gradient carbon (TCGC). The TCGC can be prepared using a UV excimer laser to induce confined, self-limited carbonization of polyimide (PI), which naturally creates a gradient distribution of graphitization degree, with graphene (Gr) layer at the top and amorphous carbon (AC) layer at the bottom.
The researchers say that the unique gradient structure of the TCGC facilitates anisotropic and non-uniform spatial thermal conductivity distribution, thereby controlling the intensity of heat conduction in different directions. Systematically experimental and numerical studies have showed the self-aligned mechanism, wherein the TCGC enables simultaneous laser absorption and directional heat conduction to non-ideal irradiated regions under non-uniform/misaligned infrared laser irradiation. This efficient thermal homogenization ensures the synchronous release of a chip across all adhesive positions on the stamp, thereby mitigating the impact of irradiation deviations on the chip transfer path.
Additionally, the periodically arranged, grayscale-controlled TCGC can selectively release microchips without pre-planned scanning paths, offering distinct advantages in chip throughput for batch selective transfer and high-tolerance to irradiation deviation in the densely arranged chip arrays.
