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

Epitaxially grown Si and Si0.6Ge0.4 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 (gm). The experimentally observed gm bimodal distribution for epi Si is corroborated and explained through a resistive network model: lower gm conduction occurs when current needs to cross a high resistance boundary, whereas higher gm is obtained when this boundary is not present.