Layout Optimization of Dual-Directional SCR for Holding Voltage Equilibrium in ESD Applications

The reverse holding voltage of high-voltage (HV) dual-directional silicon-controlled rectifier (DDSCR) is usually degraded to a very low level due to the ubiquitous substrate guard ring. In this article, two symmetrical dual-finger layout configurations of DDSCR (DDSCR-DF1 and DDSCR-DF2) are proposed to restrain the degradation of negative holding voltage. By suppressing the parasitic current paths associated with the p-type guard ring (PGR) in all directions, experimental results indicate that the DDSCR-DF2 can effectively shield the substrate parasitic effects, thereby restoring the high holding voltage characteristic inherent in DDSCR kernel. Moreover, the dual-finger layout configuration presented here can be extended to various existing HV DDSCRs, thus providing a very useful layout optimization method for HV Electrostatic discharge (ESD) engineering.