On the Multifinger Turn-On Instability in Drain Extended Vertically Stacked Nanosheet FETs Under ESD Stress Conditions

In this work, a multifinger drain extended (DE) nanosheet FET, designed on the lines of conventional drain extended MOS (DeMOS) devices, has been studied for its multifinger turn-on uniformity under electrostatic discharge (ESD) stress conditions using 3-D TCAD simulations. Detailed physical insights are developed into the performance and ESD reliability for the single-finger as well as multifinger device configurations. While the ON-current scaled uniformly with the number of fingers; current and temperature instabilities were seen in the multifinger devices under high current transmission line pulsing (TLP) stress. These instabilities, which may result in premature device failure, were found to be attributed to nonuniform finger turn-on. The physics of nonuniform turn-on in multifinger devices has been probed and on the basis of the observations drawn from the physical insights developed, novel extension fin engineering guidelines have been proposed to mitigate the nonuniform finger turn-on. Also, the impact of the proposed modifications on the ON-state transistor performance has been analyzed comprehensively.