Investigation on holding voltage of asymmetric DDSCR with floating heavy doping in 0.18 μm CMOS process

In the ESD protection design work, the most effective way to improve the holding voltage of bidirectional silicon-controlled rectifier or SCR device is to increase the distance between the cathode and anode of it. However, for DDSCR devices with multi-finger layouts, increasing this distance will result in a decrease in failure current and require a larger layout area. In this work, five types of asymmetric dual direction silicon-controlled rectifier devices with different floating heavy doping combinations are designed based on the traditional ADDSCR structure. Meanwhile, the dimensions, number of fingers, metal layout and number of CONT holes of the five ADDSCR structures are strictly kept the same, aiming at studying the influence of different floating heavy doping combinations on the performance of SCR devices and find the optimal floating heavy doping combination. Their ESD performances are predicted and verified through the two-dimensional device simulations and transmission line pulse (TLP) test results. All the five types of ADDSCR structures are designed to improve the holding voltage. From the results, the forward and reverse holding voltage of ADDSCR_PP, which is inserted floating P+ in NW and PW, are increased to 20.4 V and 17.6 V respectively, compared with the traditional devices without floating heavy doping at 14.2 V and 8.7 V. At the same time, the physical mechanism for the effect of floating heavy doping insert into NW and PW separately were investigated. Finally, the one that best meets the ESD window of automotive application is found.