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

• Published in: IEEE electron device letters 2018-12, Vol.39 (12), p.1896-1899
• Main Authors: Liu, Zhikun, Chen, Dingbo, Wan, Lijun, Li, Guoqiang
• Format: Article
• Language: English
• Subjects: Annealing; Contact resistance; Current leakage; Electrodes; Electron mobility; Gallium nitride; Gallium nitrides; GaN HEMT; gate-first approach; Gates; HEMTs; High temperature; Logic gates; Micron-scale annealing; ohmic contact; Ohmic contacts; Tin; Transistors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2018.2877717

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.