On the channel length dependence of negative bias temperature instability in nano-CMOS technology

The channel length dependence of NBTI degradation in a 65 nm CMOS technology is studied. Although it is generally observed that the NBTI degradation increases with the channel length decreasing, the role of the generated interface traps and the oxide positive charges in the NBTI channel length dependence is not clear yet. In this work, it is shown that the NBTI degradation of the B(boron) LDD devices have stronger channel length dependence as compared with the BF2 LDD devices. The channel length dependence of the oxide trapped charges density (ΔNot) and the interface trap density (ΔNit) are quantitatively estimated. Although both of the ΔNot and the ΔNit increase with the decreasing channel length, it is shown that the local ΔNit is significantly enhanced at the gate edge in B LDD devices. On the other hand, the ΔNot shows weaker channel length dependence in both B and BF2 LDD devices, as compared with the ΔNit in B LDD devices. These results imply that the enhanced NBTI degradation must be taking into consideration in the future device scaling.