Laser projection proximity transfer for deterministic assembly of microchip arrays at scale

Abstract

<p>Deterministic assembly techniques that enable programmatic and massively parallel integration of chips are essential for the development of novel electronic systems such as microLED displays. However, large-area integration of ultrathin micro-chips with high yield and transfer accuracy remains a great challenge due to the difficulties in selective transfer, adhesion switchability, and transfer deviation. Here, a "laser projection proximity transfer (LaserPPT)" technique is presented for the deterministic assembly of microchip arrays at scale. One of the remarkable features is that the transfer status between the chip and the receiver substrate evolves from the original non-contact mode to contact mode for high-precision transfer, which overcomes the strict requirements of the flatness of stamp and substrate in contact-style transfer, and flight deviation of microchip array in non-contact-style transfer. Another feature is the rapid modulation of interfacial adhesion for reliable transfer via the use of thermally expandable microspheres to form microstructures and combining with a laser-induced blister. The adhesion regulation range is over 20 times without any damage to chip arrays. The results show that the transfer accuracy has been improved substantially with a minimum relative error of similar to 0.5%. Combined with a laser beam projection system, demonstrations of LaserPPT for selective assembly of fragile objects onto challenging non-adhesive/cured surfaces in batch illustrate its potential in the high-precision integration of microscale chips at scale.</p>