The radiation response of the high dielectric-constant hafnium oxide/silicon system

We have explored the radiation response of the HfO₂/Si system with a combination of capacitance versus voltage and electron spin resonance measurements on capacitor and bare oxide structures subjected to ⁶⁰Co gamma irradiation and vacuum ultraviolet irradiation. Our studies have utilized both (100)Si and (111)Si substrate structures. Capacitors have been irradiated under both positive and negative gate bias as well as with the gate floating. We find the "electronic" radiation response of the HfO₂/Si system to be different from that of the Si/SiO₂ system. However, we find that the HfO₂/Si interface defects and their response to hydrogen are quite similar to those of the Si/SiO₂ interface defects. We also find that the HfO₂/Si atomic scale defects and their response to irradiation different from that of the Si/SiO₂ system. We find the radiation response of the HfO₂/Si capacitors to be dominated by a very large buildup of negative oxide charge. We observe comparably little, if any, generation of Si/dielectric interface trap density, though we do observe substantial densities of Si/dielectric interface trap defects. The concentration of these defects is not measurably altered by irradiation. The structure of the most prominently observed HfO₂/Si interface defects is somewhat similar to those observed in Si/SiO₂ systems. We observe comparatively little, if any, generation of slow traps/border traps/switching traps near the Si/HfO₂ interface.