AC hot-carrier effects in scaled MOS devices

AC hot-carrier effects with complete precautions against the wiring inductance noises were investigated to get a universal guideline from the viewpoints of AC conditions and device structures (single drain (SD), LDD, and GOLD). Pulse-induced-noises due to the wiring inductance of measurement systems screens intrinsic AC effects. After precautions against noises, AC hot-carrier degradation can be estimated in LDD on the basis of DC measurements. The noise is negligible for degradation when the wiring inductance is smaller than 250 m Omega . In terms of device structure dependence, for SD and LDD, enhanced AC degradation was observed during channel hot-electron (CHE) stress. No acceleration occurred with drain avalanche hot-carrier (DAHC). In LDD, this enhancement can be attributed to stronger DAHC stress during gate pulse transients, while in SD, trapping of channel hot electrons at neutral traps created at the rising and the falling edges of gate pulses acted as an additional acceleration factor. In the case of GOLD, however, no difference between AC and DC stress was seen for DAHC or CHE conditions, and CHE stress was more severe than DAHC stress, which was possibly due to a large gate current characteristic.<
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