Research On A SCR Compact Model For ESD Protection

With the continuous progress of integrated circuit technology,the problem of electrostatic discharge is becoming increasingly serious,and the protective ability of ESD devices continues to decline.The standard ESD solutions based on MOSFETs provided by wafer foundries gradually fail to meet the requirements,requiring a more robust structure as a protection scheme.As the ESD protection device with the highest robustness per unit area,SCR is considered a feasible option.However,SCR devices are not widely used for on-chip protection because of the latch-up risk and no mature device model is available.Therefore,a SCR device model needs to be presented for use by foundry.This article provides an equivalent model for SCR devices to evaluate whether they meet the requirements of the ESD device design window.This article mainly includes the following aspects of work:1.Starting from the basic theory of ESD protection,this thesis introduces the basic principles and models of ESD protection.Subsequently,the structure of SCR devices for ESD protection and the electrical characteristics of SCR devices under TLP and VF-TLP tests are introduced;2.A SPICE model equivalent circuit for SCR devices used for ESD protection is proposed.The model circuit is divided into three modules:small current module,PIN module,and switch module.The model is simple and can be constructed only through diodes,resistors,and switches.It can not only fit the breakdown point of the ESD TLP test I-V DC characteristic curve of SCR devices at low current,but also fit the self-heating effect at high current.It was verified by combining TCAD simulation with ADS simulation.By changing the device size and well doping concentration,it is proved that the proposed model has process scalability;3.Based on the equivalent circuit of the SPICE model for SCR devices used for ESD protection,a transient model of SCR devices under VF-TLP testing is proposed.Based on using the small current module of the equivalent circuit of the SPICE model of the SCR device protected by ESD as the current detection module,a new switching control method is proposed.This method achieves a slow change from a high resistance state to a low resistance state by using an inductor,and uses a single pole double throw switch to control the switching conditions from a high resistance state to a low resistance state.Finally,the model circuit is verified by combining TCAD simulation with ADS simulation.The transient characteristic model can detect the time and value of the voltage overshoot point of SCR devices under different VF-TLP voltages,enabling the model to accurately simulate the overshoot characteristics of SCR devices.