A novel robust SCR with high holding voltage for on-chip ESD protection of industry-level bus

Abstract

In an industry-level bus, strong electrostatic interference seriously threatens the reliability of chips. However, the holding voltage (Vh) and robustness of traditional silicon-controlled rectifier (SCR) cannot meet the electrostatic discharge (ESD) window of industry-level applications. To better cope with extreme environments, this paper proposes a novel SCR with high robustness and latch-up immunity for on-chip ESD protection of the industry-level RS485 bus. By incorporating a surface current diverting path into the traditional SCR, the ESD characteristics of the proposed device are significantly improved. Through two-dimensional device simulation, the ESD characteristics of traditional SCR, proposed P-Well Floating SCR (PFSCR) and proposed P-Well Grounded SCR (PGSCR) are compared, with a focus on exploring the role of surface discharge path. Three types of SCR are realized based on the 0.18 μm BCD process. The transmission line pulse (TLP) test results show that PGSCR (13.64 V) has a higher Vh and higher robustness than traditional SCR (2.13 V) and PFSCR (4.39 V). In addition, the trigger voltage (Vt1:22.9 V) and failure current (It2:18.49A) of the PGSCR fully meet the ESD window of the target chip.