Laser Processing of Micro-LEDs

This white paper reviews the critical laser-based fabrication steps needed for high volume production of next generation displays based on micro-LEDs (µLEDs) and explains why UVblade technology using the excimer laser is the optimum solution.

Nov 8th, 2018
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The speed of innovation and technology development for advanced display products is breathtaking. While large-scale investment in OLED display production is ongoing in Korea and China, there is already a next generation technology on the horizon – micro-LEDs ((μLEDs) – that may soon challenge LCD and OLED displays in some segments. This whitepaper reviews the important laser-based fabrication steps needed for high volume production of next generation displays based on micro-LEDs (µLEDs) and explains why UVblade technology using the 248 nm excimer laser is the optimum solution for several key fabrication steps.

  • Laser Lift-Off (LLO) to separate the finished μLED from the sapphire growth wafer
  • Laser Induced Forward Transfer (LIFT) to move the μLED from a donor to the substrate
  • Excimer Laser Annealing (ELA) to fabricate a LTPS-TFT backplane
  • Laser cutting at different levels of aggregation
  • Laser repair of μLEDs to address yield issues and defect rates

LLO and LIFT are techniques pioneered by Coherent and this white paper explains these two processes in significant detail. They are also discussed in the context of the multistep process required to transfer larger numbers of µLEDs from a temporary sapphire substrate to a final substrate with active matrix technology in order to assemble a display.

Figure1. Overview of µLED display assembly based on LLO and LIFT processes

In addition, the white paper explains how the unique beam uniformity and optimized dimensions of UVBlade are an ideal match for these processes, why the 248 nm excimer wavelength is perfect for processing GaN µLEDs, and how the shorter 193 nm excimer wavelength can be used for higher bandgap alternative materials such as AlN.

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