Authors: S-P. Sim, P. Guo, A. Kordesch, W.F. Chen, C-M. Liu, C.Y. Yang and K. Lee
Affilation: Santa Clara University, United States
Pages: 526 - 529
Keywords: latch-up, floating node, TCAD, SCR, ESD
A new phenomenon of floating node assisted CMOS latch-up is experimentally observed and investigated using TCAD simulation. Using test structures having parasitic bipolar transistors and an electrically floating N+ diffusion node located at various distances from a power supply node, we observed clear snapback to a low impedance state when the floating node approaches within a few microns of the power supply node. Through TCAD simulation, we found that this floating node behaves like a virtual cathode of a PNPN structure when high enough field is sustained by the underlying high resistance well. Under this high field, the diffusion node is no longer electrically floating but virtually connected to the neighboring power node by avalanche breakdown. We conclude that floating diffusion nodes can enable latch-up, if located within a few microns of a power supply node.