Effect of substrate voltage and oxide thickness on NMOSFET matching characteristics for a 0.18 μm CMOS technology

Matching characterization has been performed on 0.18 μm NMOS devices for different substrate voltage values V_b and for various oxide thicknesses T_ox, in order to determine the origin of the difference between experimental results and matching theory. Both experimental results and simulations outline an obvious tendency of mismatch to increase with T_ox and V_b. Moreover, the greater contribution of threshold voltage mismatch seems to originate from the statistical fluctuations of channel dopant number. Nevertheless, Poisson distribution of channel dopant number fluctuations does not explain the absolute amplitude of threshold voltage mismatch that could be either related to channel dopant clustering or to deviation from Poisson statistical law