Impact of SEG on uniaxially strained MuGFET performance

This work focuses on the impact of the source and drain Selective Epitaxial Growth (SEG) on the performance of uniaxially strained MuGFETs. With the channel length reduction, the normalized transconductance (gm.L/W) of unstressed MuGFETs decreases due to the series resistance and short channel effects (SCE), while the presence of uniaxial strain improves the gm. The competition between the series resistance (Rs) and the uniaxial strain results in a normalized gm maximum point for a specific channel length. Since the SEG structure influences both Rs and the strain in the channel, this work studies from room down to low temperature how these effects influence the performance of the triple-gate FETs. For lower temperatures, the strain-induced mobility enhancement increases and leads to a shift in the maximum point towards shorter channel lengths for devices without SEG. This shift is not observed for devices with SEG where the strain level is much lower. At 150 K the gm behavior of short channel strained devices with SEG is similar to the non SEG ones due to the better gm temperature enhancement for devices without SEG caused by the strain. For lower temperatures SEG structure is not useful anymore.

Research highlights► We study the influence of Selective Epitaxial Growth (SEG) on the strain efficiency. ► For short devices, a better performance was obtained for MuGFETs without SEG. ► For long devices, better results were obtained for MuGFETs with SEG. ► This study was performed at room and at low temperature.