Investigation and analysis of dual-k spacer with different materials and spacer lengths for nanowire-FET performance

- Using lower εlk for outer-spacer of dual-k structure can reduce the total capacitance as the level of single εlk spacer.
- Using higher εhk for inner-spacer of dual-k structure boosts the on-current as the same range of single εhk spacer due to the gate-fringing field effect.
- At the off-state, most of drain potential is dropped to the outer spacer capacitance and has little effect to the channel. Thus, using lower εlk for outer spacer shows the lower off-current, SSavg and DIBL.

In this work, dual-k spacer structures are investigated using a variety of materials along the high-k spacer length in detail. It is known that not only the higher permittivity materials of high-k spacer boost the on-current but also lower permittivity materials of low-k spacer effectively reduce the off-current. By compared the results of other various single spacers and dual-k spacers, it is HfO2/Vacuum dual-k spacer that shows relatively higher ION, ION/IOFF, better immunity of short channel effects and outstanding device performances.

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