Gate induced floating body effects in TiN/SiON and TiN/HfO 2 gate stack triple gate SOI nFinFETs

Abstract

In this paper, the appearance of gate induced floating body effects in triple gate SOI nFinFETs with TiN/SiON and TiN/HfO 2 gate stacks is investigated. Different floating body effects (FBEs) are found to appear under moderate accumulation back gate bias ( V BG) conditions in devices with wide and long enough geometries. In particular, a second peak in the linear transconductance ( g mf), associated with electron valence band (EVB) direct tunneling, is observed in TiN/SiON devices for front gate voltages ( V FG) around 0.8 V. Interestingly, in spite of showing about two orders of magnitude lower total gate current, a second peak in g mf is also found in TiN/HfO 2 devices for V FG around 1.1 V. Under the accumulation V BG conditions in which FBEs are observed, front gate switch drain current ( I D) transients are also appreciated. Interestingly, a change in the shape of I D transients is observed for V FG conditions in which EVB majority carriers are injected into the floating fin. The I D transients, as well as the second peak of g mf and other FBEs, are found to gradually diminish for strong accumulation V BG conditions or reduced geometry dimensions.