Metastability in multicomponent oxide transistors

Results of an investigation of bias stress metastability of multicomponent, zinc-indium and zinc-tin oxides, transistors are investigated. The bias stress as a function of various dielectrics, passivation layers, and illumination conditions indicate that for negative gate bias stressing defects often are created in the semiconductor, probably near or at the surface, particularly if the devices are unpassivated. Oxygen vacancy formation is a likely candidate. For many dielectrics, the positive gate bias metastability appears to be dominated by charge trapping within the insulator. For zinc-tin oxide devices, the kinetics of the metastability follows a stretched exponential behavior with a power law dependence on gate voltage. Correcting for the observed Meyer-Neldel behavior, the activation energy of τ is about 1.2 eV for defect generation and the disorder energy from β is about 0.06 eV. By using passivation, the best gate dielectrics and annealing protocols, we have reduced the bias stress metastability to about 0.1 V for a 25,000 s stress at 22 °C.