Comparative study of NSB and UTB SOI MOSFETs characteristics by extraction of series resistance

• Electrical characteristics of UTB (46 nm) and NSB (1.6 nm) SOI-MOSFETs are compared.
• Initial SOI channel is thinned down to 1.6 nm using a recessed-gate process.
• Drain current values were found surprisingly different by 3 orders of magnitude.
• Such a huge contrast was not found coherent with the literature.
• We built a useful model approach to interpret NSB anomalous electrical behavior.

The electrical characteristics of two kinds of n-type SOI-MOSFETs are analyzed and compared in order to build a consistent model. The first kind is an Ultra-Thin Body (UTB) device for which the channel thickness is equal to the initial SOI wafer thickness value (here 46 nm). The second kind is what we refer to Nano-Scale Body (NSB) device for which the initial SOI channel is thinned down to 1.6 nm using a recessed-gate process. The drain current values were found surprisingly different by three orders of magnitude. Such a huge contrast was not found coherent with the literature, reporting the decrease of the electron mobility with the channel thickness. We interpret our result by the probable influence of an extreme drain-to-source series resistance rather than by vanishing carrier mobility. The interpretation is sustained experimentally by the Rm–L and C–V methods. By integrating a gate-voltage dependence to the series resistance, the linear and saturation regions of the output characteristics of the NSB can be analytically derived from the UTB ones. This simple modeling approach may be useful to interpret anomalous electrical behavior of other nano-devices in which series resistance is of a great concern.