The improvement of bonding metal layers for high resolution micro-LED display application

Abstract

In this article, a resolution of 15 × 30 blue flip-chip micro-LED array with a pixel size of 20 × 35 μm2 was fabricated. The micro-LED array was hybridized with the silicon backplane via flip-chip bonding technology and liftoff process. The Au/In/Au multilayers could provide lower electrical resistivity and reduce cracks and voids at the film interface, leading to a micro-LED display that had uniform brightness and high reliability. The blue micro-LED display exhibits excellent optical and electrical characteristics, including a low turn-on voltage of 2.8 V and a brightness reach of 1.78 × 107 cd/m2 (nits) at 5 V. Additionally, there appears in the emission spectrum at a voltage of 3 V a blue shift of a peak wavelength from 455.51 to 453.96 nm. Further, the average shear strength of the micro-LED bonded by Au/In/Au multilayers increased to 2.24 g. The presented method has tremendous potential in high resolution micro-LED displays for augmented and virtual reality devices.