Investigation of hot-carrier-injection assisted TDDB and multi-stage hot-hole induced leakage current in BCD HV NMOS

With continuous improvement of the figure-of-merit (RdS
_on
vs. BVd
_ss
) in high-voltage device, HCI induced device burnout emerged. In this work, we showed that the mechanism of burnout is due to HCI assisted TDDB (HA-TDDB) as evident from various Vg and temperature dependence characterization. We demonstrated that hot-hole assisted TDDB can be initiated by a 3-stage hot-hole induced leakage current (HHLC), i.e. interface traps generation at initial stage, oxide traps at 2
^nd
stage and oxide breakdown after percolation path formation in last stage, which is different compared to hot-electron assisted TDDB. Furthermore, oblique percolation path accounted for the large Weibull slope. Negligible area-dependence at high Vd bias is ascribed to self-heating effect which mitigates impact-ionization. TCAD simulation and junction temperature at different Vd bias were performed to support the hypotheses. After thoroughly understanding the mechanism, HA-TDDB lifetime was significantly improved via process and design rule optimization.