Thin-Film Assisted Laser Transfer and Bonding (TFA-LTAB) for the Fabrication of Micro-LED Displays

Abstract

Micro-Light Emitting Diodes (Micro-LEDs) are key components in the field of next-generation display technologies. In the process of making Micro-LED displays, millions of chips need to be transferred to the driver substrate using mass transfer technology. Conventional transfer techniques, such as stamp transfer, present challenges in terms of processing efficiency and applicability due to the need for pre-prepared tethered structures and fixed chip pitch. To overcome these limitations, the t hin-film-assisted laser transfer and bonding (TFA-LTAB) technology is proposed. This technique is able to efficiently and accurately transfer Micro-LEDs from the source substrate to the driver substrate with arbitrary pitch through thin-film assistance, and electrically connects the chips through flip-chip bonding technology, which significantly improves the efficiency and reliability of the transfer and joining. The TFA-LTAB method proposed in this study integrates laser transfer and flip-chip bonding techniques. Through the TFA-LTAB process, these Micro-LEDs cultured on sapphire substrates are precisely assembled onto transparent low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs). The method successfully achieved mass transfer and bonding of Micro-LEDs with a size of 30 × 15 µm² at low temperature (180 °C) and low pressure (0.08 MPa).