SPICE Implementation of a Finite Element Method Based Model for Bipolar Power Semiconductors Armando Araújo, Adriano Carvalho Faculdade de Engenharia da Universidade do Porto (FEUP) Rua Dr. Roberto Frias, s/n 4200-465 Porto Porto, PORTUGAL Tel +351 22 508 14 00 / Fax +351 22 508 14 40 asa@fe.up.pt / asc@fe.up.pt Keywords - «IGBT», «model», «circuit simulation», «FEM». Abstract - This paper describes the methodology associated with the practical implementation, in SPICE circuit simulator, of a Finite Element Method (FEM) based model developed for Bipolar Power Semiconductor (BPS) simulation. The methodology is based on a modular approach that associates each zone of the semiconductor to a subcircuit implemented into SPICE simulator. Modeling a semiconductor is based on union of a set of subcircuit modules necessary for the different zones. Calculus of instantaneous distribution of lightly doped zones carriers (ambipolar diffusion equation (ADE) solution in space/time) is made of a group of subcircuit modules, analogue to FEM elements. The paper shows how each module is implemented and how easily elements with different sizes, topologies or physical properties are designed. Remaining semiconductor zones (highly doped emitters narrow base and MOS zones) are modeled with subcircuits using classical approaches. Voltage drops are modeled with subcircuits implementing a Boltzmann approach for junctions and a Poisson approach for depletion zones. Description for obtaining each associated SPICE subcircuit is presented. Global solution is approached by serial interconnection of these modules (each one directly related to one element of the domain). The paper concludes with simulation results showing hole/electron distribution, in time/space, in low-doped zones of PIN Diodes, BJTs and IGBTs, as well as, corresponding dynamic commutation waveforms for current and voltage. 1 Introduction This paper presents practical implementation of a modeling method for BPS. The method is based on unidimensional approach that associates each zone of the semiconductor to a subcircuit capable of being implemented in any general circuit simulator (such as SPICE), in a modular mode[1]. Modeling of a semiconductor begins with identification of the different zones that constitute the device, such as, low doped, high doped and ohmic zones, narrow bases, junction and space charge and MOS zones. For large and lightly doped zones electron/hole time/space distribution is found solving ADE with FEM [2], [3], [4], [5]. Highly doped emitters are modeled as recombination sinks using h parameters as well as narrow bases with charge control principles. Ohmic zones use knowledge of time/space carrier concentration and junction drops Boltzmann approach, space charge uses Poisson equation and MOS part of the devices is represented through standard models [6], [7], [8], [9]. After identification of these zones we just use modules that emulate their behaviour and make connections between them using boundary conditions. The paper is organized as it follows: Next section introduces circuits for ADE solution. Section 1 introduces circuits associated with solutions for narrow bases, high doped, ohmic, junction, space charge and MOS zones. Section 4 shows how to put together the obtained modules for power Diode, BJT and IGBT modeling. Finally Sections 5 and 6 present obtained results and conclusions. SPICE Implementation of a FEM Based Model for Bipolar Power Semiconductors ADRIANO CARVALHO Adriano EPE 2003 - Toulouse ISBN : 90-75815-07-7 P.1