Comprehensive study on vth variability in silicon on Thin BOX (SOTB) CMOS with small random-dopant fluctuation: Finding a way to further reduce variation

The Silicon on Thin BOX (SOTB) has the smallest V_th variation among planar CMOS due to low-dose channel. This study focused on identifying the remaining components after reducing random-dopant fluctuation (RDF) by decreasing impurities in the channel. Improving short-channel-effect immunity and body-thickness uniformity is the key to further reducing the variation. An often mentioned phenomenon, larger variability in NMOS than PMOS, cannot be explained by conventional RDF but is surely related to channel doping.