Field dependence of interface-trap buildup in polysilicon and metal gate MOS devices

The electric field dependence of radiation-induced oxide- and interface-trap charge ( Delta V/sub ot/ and Delta V/sub it/) generation for polysilicon- and metal-gate MOS transistors is investigated at electric fields (E/sub ox/) from -4.2 MV/cm to +4.7 MV/cm. If electron-hole recombination effects are taken into account, the absolute value of Delta V/sub ot/ and the saturated value of Delta V/sub it/ for both polysilicon- and metal-gate transistors are shown to follow an approximate E/sup -1/2/ field dependence for E/sub ox/>or=0.4 MV/cm. An E/sup -1/2/ dependence for the saturated value of Delta V/sub it/ was also observed for negative-bias irradiation followed by a constant positive-bias anneal. The E/sup -1/2/ field dependence observed suggests that the total number of interface traps created in these devices may be determined by hole trapping near the Si/SiO/sub 2/ interface for positive-bias irradiation or near the gate/SiO/sub 2/ interface for negative bias irradiation, though H/sup +/ drift remains the likely rate-limiting step in the process. Based on these results, a hole-trapping/hydrogen transport model-involving hole trapping and subsequent near-interfacial H/sup +/ release, transport, and reaction at the interface-is proposed as a possible explanation of Delta V/sub it/ buildup in these polysilicon- and metal-gate transistors.<
>