Impact of Mechanical Stress on 3-D NAND Flash Current Conduction

This work experimentally investigates current conduction in 3-D NAND under up to 7 GPa of externally applied compressive mechanical stress. The impact of channel crystallinity and geometry is studied by comparing four types of Si channels: polycrystalline full channel, single-crystal full channel, polycrystalline macaroni channel, and single-crystal macaroni channel. In the studied channel types, the mechanical stress was found to cause reversible degradation of
I
_ON
(up to one order of magnitude) and
I
_OFF
(up to seven orders of magnitude). Using TCAD simulations,
I
_ON
and
I
_OFF
deterioration are attributed to carrier mobility and Si bandgap decreases under mechanical stress, respectively. The simulations also suggest that both effects depend on the channel morphology, which results in a different extent of stress impact on the four studied types of Si channels.