Research And Design Of ESD Protection Devices Based On SCR And DDSCR

With the semiconductor manufacturing process entering the sub-micron level,electrostatic discharge(ESD)has become a major factor in the reliability issues of integrated circuits.In order to avoid damage to the internal circuits of the chip and the occurrence of latch-up,the ESD design window has also continued to shrink with the development of the process,which has caused the difficulty of ESD protection design to increase.Therefore,this paper aims to study and design an ESD protection device with low voltage trigger and small hysteresis.In this paper,Silicon Controlled Rectifier(SCR)and Dual-Direction Silicon Controlled Rectifier(DDSCR)were studied and designed by combining ESD theoretical analysis and device simulation in order to solve the problem that trigger voltage is too high and holding voltage is too low of the traditional protective devices.The main work includes: basic theoretical knowledge research of ESD protection design,research on the working principle and working characteristics of ESD protection devices,comparative analysis of the protection characteristics of low trigger devices and traditional devices,theoretical derivation and design analysis of SCR device holding status,DDSCR Device optimization model establishment and design analysis.Based on 0.18?m CMOS process,the innovation results of this paper are as follows:(1)Based on the strong robust SCR structure,in view of the problem that traditional LVTSCR(Low Voltage Triggering SCR)device is prone to latch-up,a novel LVTSCR device structure with embedded PMOS is proposed in this paper(EPMLVTSCR,Embedded PMOS-LVTSCR).EPM-LVTSCR is turned on by GGNMOS(Gate Grounded NMOS)low trigger voltage feature,and the trigger path of the novel device is relatively short,which can further reduce its trigger voltage.At the same time,the normally open PMOS tube embedded constitutes an additional current path,which can effectively suppress the positive feedback effect of the two parasitic transistors in the SCR path,thereby improving the holding voltage of the device.The simulation results show that compared with traditional LVTSCR devices,the trigger voltage of EPM-LVTSCR reduced by 7.8%,and holding voltage of EPM-LVTSCR increased by 2.52 V.(2)Based on the DDSCR structure of bidirectional protection,in view of the problem that the LT?DDSCR(Low-Triggering DDSCR)device has a low holding voltage,a novel LT?DDSCR device structure with embedded dual NMOS tubes(MHVDDSCR,Multipath High-holding Voltage DDSCR)is proposed.Based on the structural symmetry and bidirectional low trigger voltage characteristics,MHVDDSCR promotes the NMOS tube to open through electrical stress,and forms a shunt path to cause the lack of carriers on the SCR path,so as to increase the device holding voltage.The simulation results show that compared with traditional LT?DDSCR devices,the trigger voltage of MHVDDSCR reduced by 5.2%,and the holding voltage of MHVDDSCR increased by 5.03 V.