Hot-carrier lifetime dependence on channel width and silicon recess depth in N-channel metal-oxide-semiconductor field-effect-transistors with the recessed local oxidation of silicon isolation structure
Narrow width n-channel metal-oxide-semiconductor field-effect-transistors (nMOSFETs) fabricated with recessed local oxidation of silicon (R-LOCOS) isolation structures and deeper field oxide recess exhibit less hot-carrier degradation as compared to wide channel devices when stressed under the maximum substrate current condition. Through the investigation of many possible causes, such as channel stop doping effect, lateral channel electric field, mechanical stress effect, and recess depth effect, the cause of the smaller degradation in narrow channel nMOSFETs was found. This was due to a hole-attractive vertical electric field across the width of the narrow channel nMOSFET, which results in less interaction of the channel hot electrons with the silicon-silicon dioxide interface, and thus contributing to less interface-state generation. It was also found that a deeper field oxide recess in narrow channel nMOSFETs leads to lesser hot-carrier degradation, which is possibly related to the reduced impact ionization rate in the channel.