Micron-Scale Annealing for Ohmic Contact Formation Applied in GaN HEMT Gate-First Technology

Abstract

High-temperature thermal annealing process for ohmic contact hinders the development of monolithic integration of heterogeneous functional devices as well as gate-first approach for the GaN transistor. Other than reducing processing temperature, we developed a selective annealing method so that temperature-sensitive parts were not thermally affected. Here, we report a micron-scale annealing method by focused laser for ohmic contact in a GaN heterogeneous system/device. The micron-scale annealing method enabled the formation of a relatively thick TiN layer (35 nm) at the metal–semiconductor interface. As a result, a low contact resistance of 0.3 $\Omega \cdot \text {mm}$ was achieved. The miniaturized annealing method was applied to the gate-first approach for GaN high electron mobility transistor (HEMT). A better performance of larger current output, smaller gate leakage ( $1\times 10^{{6}}$ times smaller), and larger dynamic range of HEMT was hence obtained.