The statistical analysis of substrate current to soft breakdown in ultra-thin gate oxide n-MOSFETs

In this work, the characteristics of the substrate current (I_sub) to soft breakdowns (SBDs) in n-MOSFETs were studied under constant voltage stress (CVS). The jump of the substrate current can be regarded a soft breakdown (SBD) event. Both the time-to-breakdown (t_BD) obtained from I_sub jumps and the SBD substrate current increment (ΔIsub_(SBD)) followed Weibull distribution. The Weibull slopes of t_BD and ΔIsub_(SBD) increased with increasing test temperature, but the temperature dependence of the characteristic ΔIsub_(SBD) (63% ΔIsub_(SBD)) is different. On the other hand, the relation between the I_sub and I_g (gate current) alter SBDs was studied. Both the forming process and jumps of I_sub under CVS were described and explained by the variable frequency light pumping effect (VFLP).