Research Of ESD Protection Device Based On SCR Structure

Silicon Controlled Rectifier(SCR)structure is an important semiconductor device for electrostatic discharge and power electronics.Silicon Controlled Rectifier has many applications in power electronics as heavy current switches.At the same time,it can also be used to form ESD(Electro-static Discharge)protection network on the input interface and low impedance shunt devices on the power rail.SCR device can discharge more current than general devices in a small area,which has the advantages of high robustness,small area,and low dynamic resistance.However,the low holding voltage of traditional SCR device will cause the latch-up effect,which seriously restricts the application of SCR device in ESD protection.Aiming at the problem of latch-up in traditional SCR device,based on the ESD design window of high holding voltage and high holding current,two ESD devices based on SCR structure are proposed in this thesis.Firstly,based on the ESD design window of high holding voltage,a high holding voltage ESD device based on SCR structure embedded with additional NPN is proposed.The conduction process and physical mechanism of the structure are analyzed in detail.Then,the proposed device is simulated,the characteristics of current and electric field in each stage are obtained,and the reason why the device obtains high holding voltage is further discussed.Finally,the parameters of the device are optimized through simulation,so that the trigger voltage of this device is 20 V,which can provide ESD protection for 12 V power supply.The holding voltage is greatly increased from about 2V to 13.5 V.The latch-up problem of SCR structure is effectively solved.The on-resistance of the device is very small,so the device can obtain better ESD robustness.Then,based on the ESD design window of high holding current,this thesis proposes a high holding current ESD device with ZP implant based on the SCR.And,this thesis analyzes the physical mechanism of the structure through modeling,gives the expression of the trigger current,and analyzes the equivalent circuit under different currents.Then,the characteristics of the structure are simulated by simulation software to verify the consistency with the theoretical analysis.And the parameters of the device are optimized by simulation.Finally,the trigger voltage of the device is about 8.5 V,which can be used for ESD protection of the 5 V data transmission port.The device obtains a high holding current which is about 15 times higher than that of traditional devices.If the device finger is 200 ?m,the holding current can reach about 300 m A.And the on-resistance of the device is very small,which solves the latch-up problem while also having excellent clamping performance.