Improved analysis and modeling of low-frequency noise in nanoscale MOSFETs

Extensive investigation of the low-frequency noise in n-channel and p-channel MOSFETs, with high-k gate stack and channel length varying from 1.8 μm down to 26.4 nm, has been carried out. The results demonstrate that the carrier number fluctuation with correlated mobility fluctuations describes accurately and continuously the 1/f   noise for all operation regions, i.e. from weak to strong inversion and from linear to saturation. It has been found that the product of the Coulomb scattering coefficient and the effective carrier mobility αscμeffαscμeff is constant over a wide range of the drain current due to the interplay of the Coulomb scattering coefficient αsc and the effective carrier mobility μeff variations. In addition, a non-linear increase in the square root of the input gate voltage noise with the gate voltage overdrive was observed explained by the surface roughness scattering. The overall results lead to an analytical expression for the 1/f noise model, enabling to predict the noise level of a transistor with any channel dimensions using its transfer characteristic. This finding makes the noise model suitable for circuit simulation tools.

Graphical abstractThe investigated devices are n- and p-MOS transistors issued from 28 nm bulk CMOS technology. The gate stack consists of TiN as metallization and Hf-based dielectric as gate oxide with an equivalent oxide thickness (EOT) 14 Ǻ and 17 Ǻ for the n- and p-MOS transistors, respectively. The channel length (L) is lying in the range of 0.0264–1.803 μm and the channel width (W) is 0.9 μm. For all operation regions, a generic MOSFET compact correlated mobility fluctuations noise model is constructed based on a single equation: SVg=SVfb1+ΩIdgm,with two physical parameters namely, SVfb related to the oxide trap density and Ω=αscμeffCoxΩ=αscμeffCox related to the effective Coulomb scattering coefficient αscμeffαscμeff and gate oxide capacitance. Both parameters can be extracted experimentally from a plot of SVg versus Id/gm in linear and/or non-linear operation regions.The model enables to predict the noise level from the transfer characteristic of a transistor with any channel dimensions, making it suitable for circuit simulation tools.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Low-frequency noise in nanoscale n-channel and p-channel MOSFETs. ► Constant product of the Coulomb scattering coefficient and the effective carrier mobility. ► Modeling in all regions of operation.