Through silicon via-hole-based thin-film light emitting diodes

Abstract

A thin film GaN-based LEDs has been fabricated on a silicon substrate with periodic via holes formed by a laser drilling process. GaN-based LEDs grown on sapphire substrate are successfully bonded and transferred onto Si substrate with periodic via holes using Au-Sn wafer bonding followed by grinding, chemical mechanical polishing (CMP) and dry etching. The bonding medium comprises Au-Sn multilayer composite deposited directly on the object to be bonded. Sapphire substrate is detached from GaN-based LEDs epi-layer by using mechanical grinding, CMP and dry etching process. The indium-tin-oxide (ITO)/Al are deposited to improve contact resistance with p-GaN and optical reflectivity. Using the reflective metal Al layer, the light emanating from the active region towards through-silicon vias (TSVs) substrate could be reflected and escaped from the semiconductor through the top surface. The periodic via holes are formed by a laser drilling technique; p-contact metals are deposited onto the backside of silicon substrate to form vertical electrical interconnections between silicon substrate and p-GaN layer. The through silicon via-holes-based thin film LED can achieve better electrical performance, and sustain a higher input current level than the conventional GaN/Sapphire LED due to the formed vertical electrical interconnections and the higher thermal conductivity of TSVs substrate.