SPICE Macro-Modeling Of High-Voltage LDMOS Based On Chebyshev Theory

With the rapid development and application of PICs (Power Integrated Circuits),power devices also make great progress. They are used more and more rapidly in themarket. The high voltage bulk silicon LDMOS(Lateral Double-diffused MOSFET)can be well applied in the power circuits for its good performances about thebreakdown voltage and on-resistance and its easy integration in the standard CMOSprocess flow. So many people begin to pay more attention to LDMOS in recent years.Device models are essential for circuit simulations. Whether the results ofsimulations could predict the PIC's performance exactly, the precise HV device modelwas important and wanted. Because of the variety and complexity, at present, theamount of HV models is limited for PIC Computer Aided Design (CAD). Therefore, itis necessary and urgent to establish the SPICE modeling for PIC CAD.Conventional SPICE modeling of HV device relies on the standard of element ofequivalent circuit, the precision of simulations relies on the topological structure ofequivalent circuit. Meanwhile, because the standard element of equivalent circuit cannot reflect exactly the particularity of HV device, so the result of simulation canhardly satisfy the request of PIC CAD. This dissertation presents a methodology forSPICE macro-modeling of high-voltage LDMOS.First, according to the static characteristics of device and basic semiconductortheoretics, the optimized parameters of LDMOS were obtained with the help ofnumerical simulation software -MEDICI. Simulation results show that the designedLDMOS has a lower on-resistance while maintain high breakdown voltage. Second,considering dynamic characteristic of LDMOS, the physical operation mechanismwas analyzed and then capacitance's physical model was proposed, which can helpfor large signal and transient device analysis. Third, the obtained I-V and C-V modelswere fitted by MATLAB using Chebyshev theory, which was the first time so far aswe know. At the end, a new equivalent circuit macro model was presented which canbe embedded in SPICE simulator. It was testified that the errors between mathematic model, SPICE macro-model and MEDICI simulation are within 5% and 10%seprately.Through these work, a universal method is formed to set up device's SPICEmacro model. This method also can be extended to high voltage DMOS and otherspecial devices for CAD design in high voltage integrated circuits.