Research On Dual-directional ESD Protection Device Based On SCR Structure

ESD(Electro-Static Discharge,ESD)is a common natural phenomenon in daily life.In the field of integrated circuits,electrostatic discharge can cause various failure problems of integrated circuits,greatly reducing its reliability.As device scale continue to shrink and critical size continue to decrease,the risk of electro-static-determined damage increases,ESD protection design is becoming increasingly important.Silicon controlled rectifier(SCR),due to its high ESD current per unit area,is very popular in the field of electro-static protection.With the development of electrostatic protection design towards the full chip and system level direction,and area efficiency consideration,the SCR has been developed a dual directional conductive design,that is,a dual directional SCR(DDSCR).The traditional single directional SCR has the disadvantages that the trigger voltage is too high and the holding voltage is low,and it is easy to be latched up so that the device cannot be turned off.The traditional bidirectional SCR based on this structure also has the same defects.In order to improve the ESD design window of the DDSCR,based on the 0.25 um BCD process,this paper have studied the single directional SCR,LVTDDSCR(Low Voltage Triggered DDSCR)and STDDSCR(Segment Technology DDSCR).In this process,the 12 V N-type MOS BV can reach 21 V and the P-type MOS BV is 23 V or more.The design window in this article mainly considers the case where the protected device is a conventional 12 V device,limit the TLP IV curve between the operating voltage and BV.The main content of this article is as follows:1.Modeling analysis and simulation of SCRThis paaper modeled the working principle of the single directional SCR structure and analyzed its turn on characteristics,clamping characteristics and breakdown characteristics.This paper makes several simulation researchs on LVTSCR and NMOS embedded LVTSCR,which are typical modified structures of single directional SCR.Among them,for the NMOS embedded LVTSCR structure,this paper leads out the gate end separately and analyze its working characteristics under different gate voltages.2.Research on LVTDDSCRFor the LTVTDSCR structure,based on its low holding voltage characteristic,our research mainly on layout structure parameters and changes in device structure to improving it.From the test results,several optimization directions can provide ideas for the future design of LVTDDSCR devices.3.Research on STDDSCRFor the STDDSCR structure,this paper focus on the impact of changes in N + and P + islands on TLP test results,including increasing the number of islands under the same proportion,symmetric and asymmetric arrangement of N +,P + and different sizes of N + and P + Changes in proportion.Finally,the structure of inserting floating FN + into the N-well of STDDSCR is also studied.Besides,based on STDDSCR,the N + and P + islands were misaligned in the Y direction,and two different structures were obtained and studied.Compared with the original STDDSCR structure,the current capability of these two dislocated structures has been significantly improved,and it has a better design window.