The Silicon Nitride Film Formed by ECR-CVD for GaN-Based LED Passivation

Abstract

Most GaN-LED epilayers are grown on sapphire, which is a kind of insulating substrate. From the top view, a GaN-based LED has two bonding pads, one for p-type conduction and the other for n-type conduction. These pads would affect the packaging yield because it is probable to touch the p-type material when a conducting wire is bonded to the n-pad. Besides, the reactive ion-etched sidewall is easily contaminated or adsorbed by moisture when exposed to the air. Consequently, a passivation layer is necessary to isolate these conduction paths. In this paper, we used electron cyclotron resonance chemical vapor deposition (ECR-CVD) to form the silicon nitride (SiN x ) passivation film at room temperature. The film was patterned by lift-off process and the surface of the whole wafer was covered except the bonding pads. After passivation, no distinguishable variation was found in the statistical data of forward voltage and leakage current, but the illumination intensity was raised by at least 6%. The bonding yield and reliability would be increased much. The change of electrostatic discharge (ESD) characteristics was also investigated.