Reliability and failure analysis of AlGaN/GaN HEMT with NiPtAu and PtAu gate

By comparing the reliability of 150 nm AlGaN/GaN HEMTs with PtAu gates to devices with NiPtAu SiN assisted gates, it was found that PtAu gates are more stable in terms of gate leakage current increase under HTRB step stress test and show smaller spread of the extrapolated lifetime values during long-term DC stress tests. An activation energy of 1.39 eV (1.97 eV) and a lifetime of around 107 h at Tch = 175 °C and Vd = 30 V has been extrapolated for devices with PtAu (NiPtAu) SiN assisted gate. By TEM cross sectioning and EDX mapping analysis of aged devices, the degradation of NiPtAu gate devices was attributed to a stress-induced local oxidation of the SiN passivation on the drain side of the gate foot. An activation energy of 1.15 eV and a lifetime of 5 · 104 h at Tch = 175 °C and Vd = 15 V has been extrapolated for devices with 100 nm T-gate reference technology. The faster degradation of the T-gate is possibly caused by a higher lateral electric field at the gate foot. T-gate reference technology lifetime is increased by more than an order of magnitude by reducing the drain voltage to 10 V.