Integration and Electrical Evaluation of Epitaxially Grown Si and SiGe Channels for Vertical NAND Memory Applications

Epitaxially grown Si and Si
_0.6
Ge
_0.4
are integrated as replacement of poly-Si channel in vertical cylindrical transistors for vertical NAND memory application, in order to investigate the impact of the grain boundaries on current conduction. Epi-Si outperforms both poly-Si and Epi-SiGe channels, resulting in the best conduction, with large improvement on both sub threshold swing and transconductance (g
_m
). The experimentally observed g
_m
bimodal distribution for epi Si is corroborated and explained through a resistive network model: lower g
_m
conduction occurs when current needs to cross a high resistance boundary, whereas higher g
_m
is obtained when this boundary is not present.