FAILURE MECHANISMS OF GAAS-MESFETS WITH CU REFRACTORY METALLIZED GATES/

The DC performance of Cu-based GaAs MESFETs with Au/Cu/Ti and Cu/TiW m etallized gates has been characterized after accelerated stress testin g up to 250 degrees C and anneals of 1000 hours. A failure mode has be en shown to result in a decrease in I-DSS, g(m) and V-p and an increas e in channel resistance as a function of annealing temperatures. Back- etch results show that the gate Cu/TiW/GaAs has less interfacial degra dation than Cu/Ti/GaAs gate, which is in agreement with DC measurement . However, the obvious oxidation of Cu overlayer after 250 degrees C a nneal was found, which leads to a large increase in gate resistance, f urther causes the apparent degradation of device performance for the d evices with the exposed Cu/TiW gate. (C) 1997 Elsevier Science Ltd.