Design of high robustness DDSCR with embedded gate-controlled diodes and Schottky diodes

Abstract

Due to the harsh working environments of Input/Output (I/O) pins, the electro-static discharge (ESD) protection devices of these ports often require high robustness. To design highly robust ESD protection devices with dual polarities, the Gate-controlled dual direction silicon controlled rectifier (GCDDSCR) and a DDSCR embedded with Schottky barrier diode (SBD-GCDDSCR) structures are designed and studied in this article as standalone devices for primary protection. The gate-controlled diodes and Schottky diodes are integrated into the simple DDSCR structure to enhance its robustness while reducing the on-resistance. The inclusion of gate diodes introduced an additional current path near the surface, improving space utilization in the longitudinal direction of the device, and the addition of Schottky junctions placed adjacent to the Anode and Cathode can provide additional electron extraction paths. Both methods contribute in a more uniform current distribution, improving the robustness of the device. Two-dimensional device simulation based on a classical set of equations was employed to investigate its electrical behavior during an ESD event. Based on the 0.18 μm CMOS process, all structures were fabricated into 6-finger devices with a finger length of 50 μm. The Transmission Line Pulse (TLP) testing method was used to evaluate their ESD characteristics, revealing that the addition of the gate-controlled diodes and Schottky shunt paths improved robustness. The proposed SBD-GCDDSCR structure demonstrated superior robustness under ESD stress, with a failure current exceeding 19 A in both forward and reverse directions, and its V_t2 in strong saturation regime is around 48 V.