SiC LBJT SPICE Modeling And Its Application In Power Integrated Circuits

Power integrated circuits(PICs)are gradually developing in the direction of greater power handling capabilities,higher operating temperatures,higher operating frequencies and lower power losses.Silicon carbide devices become better choices for the development integrated circuits and the frontier of subject research,since they have the advantages of better material and electrothermal performances.Silicon carbide lateral bipolar junction transistors(SiC LBJT)have become one of the important candidates for designing power integrated circuits,because of its advantages such as high temperature resistance,ability to safe from problems related to gate oxide reliability,relatively simple circuit design,and mature fabrication processes.To design the power integrated circuits,the biggest challenge is to establish accurate device model.However,due to the significant differences in band gap,thermal conductivity,and saturation drift velocity between SiC and Si materials,the mature Si BJT Gummel-Poon model is not suitable for SiC BJT.At the same time,the integrated SiC LBJT substrate will produce parasitic capacitance,which will affect the charge storage effect inside the device and change the switching time.The capacitance parameters considered in SPICE model based on traditional Gummel-Poon model are not adequate to describe the switching characteristics of the SiC LBJT.Therefore,it is urgent to improve the standard Gummal-Poon model,and add other components or functional modules to characterize the capacitance effect of SiC LBJT substrate,and to establish a more accurate SiC LBJT SPICE model.Firstly,the vertical and the lateral SiC BJT are compared,and the basic structure,working principle and electrical characteristics of the SiC LBJT are analyzed.Considering that the epitaxial layer and semi-insulator of SiC LBJT will have impact on the charge storage effect of the device,the equivalent method for internal parasitic capacitance is adopted.Meanwhile,the diffusion capacitance and substrate capacitance are used to characterize the transit time and delay time of the device.Based on analysis above,the typical static characteristics,switching process,charge-control equation and switching time parameters of SiC LBJT are summarized,which lays a theoretical foundation to model accurately.Secondly,considering the substrate effect of SiC LBJT,an improved SiC LBJT SPICE model is proposed to overcome the disadvatages of applicability and accuracy of the Gummel-Poon model.The improved SPICE model takes into account the relevant parameters of transit time,and abstracts the influence of the epitaxial layer and the semi-insulator as the capacitance between the LBJT electrode and the substrate,which improves the accuracy of the model.Based on the measured data and simulation results,the optimized fitting method is used to extract the model parameters,and the static and dynamic characteristics of the model are verified in the LTspice simulation software,which achieves a good agreement between the simulated waveform and the measured results.Finally,the established SPICE model of the 0.04mm2 SiC LBJT is applied to design integrated circuits in LTspice,including an integrated NOR gate,an integrated NAND gate and a Schmitt trigger.The static and dynamic performances of the integrated circuits are analizied.The results show that the three kinds of circuits can run well,and the results are consistent with the expectation,which is valuable for subsequent layout design and fabrication processes.