Comprehensive Study for OFF-State Hot Carrier Degrdation of Scaled nMOSFETs in DRAM

In this paper, comprehensive study for OFF-state hot carrier degradation of scaled nMOSFETs in DRAM was examined using devices with different effective channel doping concentration (N
_eff
) and gate oxide thickness (T
_ox
). Higher N
_eff
, less negative source voltage (V
_s
), and more negative body voltage (V
_B
) improved the OFF-state degradation for devices with a thick T
_ox
of 6.0 nm. On the other hand, higher N
_eff
and more negative V
_B
increased the OFF-state degradation for devices with a thin T
_ox
of 2.2 nm. The results for the OFF-state degradation were compared to the ON-state hot carrier degradation to understand the physical mechanism. Our founding indicates that techniques using a lower N
_eff
for nMOSFETs with a thin gate oxide thickness can be a key parameter to improve reliability for scaling of core transistor in DRAM.