HYDROGEN CONCENTRATION AND INTERFACE STATE GENERATION DUE TO IONIZING-RADIATION IN ALUMINUM AND POLYSILICON GATE MOS DEVICES

Interface state generation due to vacuum ultraviolet (VUV) irradiation and the influence of photoinjection during annealing are studied on M OS transistors with semitransparent aluminum gates. The results are co mpared to the degradation behavior of Al and polysilicon gate MOS capa citors after x-ray irradiation. Hydrogen depth profiling reveals signi ficant differences in hydrogen content at the gate/SiO2 interface for the two gate materials. Additional interface states are created during a post irradiation annealing step introducing molecular hydrogen. We observe a different degradation behavior in vacuum irradiation experim ents that depends on the availability of molecular hydrogen. The hydro gen contamination layer at the Al/SiO2 interface is thought to be a so urce of H-2 in Al gate devices.