Impact of strain and channel orientation on the low-frequency noise performance of Si n- and pMOSFETs

Mobility and low-frequency (LF) noise were studied in tensile strained Si n- and pMOSFETs fabricated on relaxed SiGe virtual substrates. Both the impact of the channel orientation (〈1 1 0〉 or 〈1 0 0〉 on (1 0 0) Si) and the tensile strain were carefully investigated. Two types of virtual substrates were used; a thin relaxed SiGe layer (20% Ge) and a thick one (27% Ge). The strained Si nMOSFETs fabricated on the thin substrate showed similar LF noise level as in the reference devices, whereas the thick substrate caused severely increased LF noise in the nMOSFETs. The latter was linked to the higher Ge concentration and explained by possible misfit dislocations and increased defect densities, likely resulting from strain relaxation caused by ion implantation damage. On the other hand, considerably lower LF noise was achieved in the pMOSFETs on the thick SiGe. The channel orientation was not found to have a significant influence on the LF noise performance in any of the studied devices.