| The manufacturing of integrated circuits(ICs)involves many procedures such as circuit design,material synthesis,device manufacturing,packaging and testing.The entire industry chain has created and strengthened an unbreakable interlinked feature among ICs.The reliability testing of the ICs is an important step to ensure their normal operation.Electrostatic discharge(ESD)is one of many factors affecting product reliability,which is ubiquitous.A customized ESD protection chip needs to be designed to ensure its normal operation.Process size scaling poses new challenges to the design of ESD protection devices.ESD protection design mainly adopts device simulation,which lacks direct evidence of the relationship between microstructure and device performance and ignores the material problems involved in the production process.Once the production process is not match,the ESD protection device will fail eventually,which is high cost and time-consuming.Since the damaged area can be observed by the failure analysis technology based on microscopic technology,the analysis results can effectively feedback the failure mechanism of the device,which is commonly used in the design optimization of the device.Based on this technology,this thesis studies the failure mechanism and structure optimization of novel ESD protection devices.The contents and results are as follows:(1)The reliability of diode-triggered silicon controlled rectifiers(DTSCR)based on 0.3-micron technology node is studied.One of the reasons induced the failure is that the thermal expansion coefficient of the substrate and the isolation material does not match,causing the formation of a new leakage path.Taking DTSCR as an example,the ESD process is simulated by transmission line pulsing(TLP)method.First,the abnormal behavior of leakage current is found.Then X-ray microscope is used to locate the terminal part and the middle part of the SCR area of DTSCR as the failure area,and the size is at micron scale.In addition,the optical beam induced resistance change(OBIRCH)technology is used to locate the micron-level leakage point in the failure area.According to the positioning results,we prepare the transmission electron microscope(TEM)samples by using dual-beam focused ion beam(DB-FIB).Further analysis finds that the cracks in silicon substrate forms a new leakage path,the transverse width of the crack reached 14.5 microns,which is the key factor to cause the leakage left deviation.(2)The reliability of the novel enhanced modified lateral SCR(EMLSCR)based on 65 nm technology node is studied.One of the reasons induced the failure of is that the silicide layer is melted to form conductive filaments leading to leakage phenomenon.Taking EMLSCR as an example,the ESD process is simulated by TLP testing.The critical failure morphology is captured.The leakage position is preliminarily located by OBIRCH technology,and the TEM samples are accurately cut by DB-FIB technology.Through the above defect location methods,the defect morphology and chemical composition analysis of the sample after breakdown are captured.The distribution of uneven metal filaments found in the SCR region.It is speculated that the double stack of parasitic NPN path and SCR path on cathode N+ is the reason for more serious damage than anode P+.Metal silicon melting induced by electrical stress breakdown is the essential factor of device failure.Refer to the above failure causes,the technology computer-aided design simulation software is used to verify the operation processes of the device.The robustness of the device is improved by increasing the width of the cathode N+.The comparison results of lattice temperature and current density before and after optimization confirm the effectiveness of this method.In summary,this thesis focuses on the reliability of DTSCR and EMLSCR based on microscopic technology and reveals the failure mechanism of DTSCR and EMLSCR.This thesis is helpful to promote reliability research on ESD protection devices. |
PDF Full Text Request