| In recent years, VLSI process technology is developed to nanometer scale continuous. The parameters of MOSFET, such as channel length and width, junction depth and gate oxide thickness are scaling down. But in some electric circuits such as I/O, the supply voltage can't be scaling down, and then more seriously HCI effect may occur. Hot carriers injection induce lots of traps in Si-SiO2 interface and oxide, which make the MOSFETs'drive capability decrease with increasing operating time. What's more, it will cause the parameters such as threshold voltage and mobility shift unceasingly(threshold voltage will increase, and mobility will decline), even lead to the MOSFET failure at last.Several reliability models of HCI, such as Isub/Id model (Hu's model), Vd model, substrate current model, have been proposed. These models are established under the failure criteria established by the reliability engineers. According to measured degradation of device parameters and the stress time, the device lifetime under the corresponding stress conditions is determined, the linear relationship between the device lifetime and stress variable is achieved, and further get the necessary constant. The lifetime under normal working conditions can be achieved after extrapolating. These models calculate device lifetime without describing the change of device performance with stress time caused by hot carrier effect.Since the IC design and fabrication rely increasingly on the EDA software, but it can be applicable to the EDA software reliability model is not yet presented. U.C Berkeley's BSIM3v3 model is an industry standard model, but it is found that BSIM3v3 model can't describing the change of device performance with stress time.According to the distortion of the BSIM3 above, a new reliability model based on SPICE BSIM model is presented in this paper(abbreviation HCI model). It can be describing the change of device performance with stress time. The traditional process MOSFET have been taped out with 0.5um 5V nMOSFET technology, and the data of different stress and stresstime have been collected by Agilent HP4156 system, Cascade S300 probe station, and ICCAP software.The target device is choosed and four stress accelerated testing is applied. in this paper.In this work, hundreds of BSIM3v3 model parameters are analyzed, eleven parameters primarily affected by HCI are extracted and optimized in original BSIM3v3 source code (four relationship to stress is Ua,Ub,Vsat,Pclm, and seven relationship to stresstime is Vth0,K1,Ags,A0,μ0,μc,Keta).Eleven equations are updated to BSIM3v3 free source code after that,use Visual C++SPICE to compile source code from modified BSIM3v3 library so as to build a simulator,set this simulator as the system default simulator, then parameter extractions can be made by modified new SPICE BSIM3v3 model through ICCAP2008. The model of this research is different from lifetime evaluation model described above in calculating the device lifetime according to the failure criteria as well as evaluating device performance variation with time, just like a common SPICE model evaluating the performance of fresh devices... |
