55.4: MicroLED ‐ High Throughput Laser Based Mass Transfer Technology

Laser Lift‐Off Technologies for Ultra‐Thin Emerging Electronics: Mechanisms, Applications, and Progress

“…As shown in Figure a, Haupt et al. [ 99 ] demonstrated a UV excimer laser mask‐based high‐precision imaging system for processing GaN‐based Micro‐LEDs down to a few micrometers using a UVtransfer device. Throughput is linearly related to the number of chips that can be processed with one laser shot.…”

“…a,b) Reproduced with permission. [ 99 ] Copyright 2021, Wiley. c) Schematic diagram of selective LLO controlled by the amount of defocusing of the laser beam.…”

“…The rational selection of laser processing parameters such as wavelength, pulse width, defocus amount, and optical system enables layer-selective LLO processing of functional thin films compared to other exfoliation methods from radiative or non-radiative heat sources. [95][96][97][98][99][100][101] As shown in Figure 2a-c, the working principles of the mainstream layer-selective LLO technologies all require that the photon energy (depending on the wavelength) be higher than the bandgap energy of the response material and lower than that of the carrier material. This enables selective onset of absorption of photon energy in the responsive material to separate ultrathin device layers by selective laser ablation and evaporation of strongly absorbing interfacial regions.…”

“…To shrink Micro-LEDs size and improve the processing accuracy, it is necessary to selectively transfer Micro-LEDs grown on wafers with the smallest channel widths onto substrates and change the pitch accordingly. As shown in Figure 15a, Haupt et al [99] demonstrated a UV excimer laser mask-based high-precision imaging system for processing GaN-based Micro-LEDs down to a few micrometers using a UVtransfer device. Throughput is linearly related to the number of chips that can be processed with one laser shot.…”

“…For example, through methods such as homogenized flat-top laser beams and multibeam parallel processing to increase throughput and improve laser energy utilization efficiency. Tailoring the shaping of the [99] Copyright 2021, Wiley. c) Schematic diagram of selective LLO controlled by the amount of defocusing of the laser beam.…”