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

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Abstract
We have explored the radiation response of the HfO/sub 2//Si system with a combination of capacitance versus voltage and electron spin resonance measurements on capacitor and bare oxide structures subjected to /sup 60/Co 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 HfO/sub 2//Si system to be different from that of the Si/SiO/sub 2/ system. However, we find that the HfO/sub 2//Si interface defects and their response to hydrogen are quite similar to those of the Si/SiO/sub 2/ interface defects. We also find that the HfO/sub 2//Si atomic scale defects and their response to irradiation different from that of the Si/SiO/sub 2/ system. We find the radiation response of the HfO/sub 2//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 HfO/sub 2//Si interface defects is somewhat similar to those observed in Si/SiO/sub 2/ systems. We observe comparatively little, if any, generation of slow traps/border traps/switching traps near the Si/HfO/sub 2/ interface.