Temperature dependence of soft breakdown and wear-out in sub-3 nm SiO/sub 2/ films

A comprehensive time-dependent dielectric breakdown study was conducted on sub-3 nm SiO/sub 2/ films over a temperature range from 22/spl deg/C to 350/spl deg/C. Two breakdown modes were observed in current versus time characteristics and low voltage I-V curves depending on device area and stress voltage. Larger device areas and lower stress voltage produced higher occurrences of soft/noisy breakdown events while smaller device areas and larger stress voltages produced harder/thermal breakdown events. Stress temperature did not affect the breakdown mode. The results indicate that both breakdown modes exhibit the same thermal acceleration if the first occurrence of current noise is used as a breakdown criteria for those devices exhibiting noisy breakdown. The observed strong dependence of the thermal activation energy on gate voltage may explain previous reports of increased temperature acceleration for ultra-thin films.