Radiation-Induced Interface-State Generation in MOS Devices

The time dependence of interface-state generation in metal and polysilicon gate MOS devices has been investigated. In contrast to results obtained by previous workers, we find that for metal gate devices there can be a significant "prompt" component of interface-state buildup. This prompt component is accompanied by a slow buildup of interface-states, which is still increasing at 500 sec., and is similar to what has been observed previously. For polysilicon gate capacitors there is a time dependent component of interface-state generation that is considerably more rapid than for metal gate devices. The time dependent component of interface-state generation for polysilicon gate capacitors begins within 10 msec after a pulse of radiation and is more than 50 percent complete by 1 sec. The rapid buildup of interface-states for polysilicon gate devices, and the prompt component for metal gate devices, will affect the electrical response of MOS devices in a weapon environment. The existence of more than one component of interface-state buildup indicates that more than one mechanism may be responsible for interface-state generation.