Investigation on Excess Carrier Distribution for a Quasi-2D Lumped-Charge Insulated Gate Bipolar Transistor Model

Abstract

The lumped-charge (LC) IGBT model provides an effective and efficient way to simulate its switching behaviors. However, most of existing LC models are based on a 1-D solution and thus, cannot account for the difference of carrier concentrations between under the P-well and gate. Except for that, most of the existing LC IGBT models focus on total quantities of excess carriers rather than the distributions. Both factors would undermine the accuracy of the LC IGBT model. Therefore, a quasi-2D LC IGBT model that retains the simplicity of the 1-D solution in the drift region is proposed. First, validated by TCAD simulation, a charge concentration expression for a planar gate structure as a function of the intercell region geometry is derived to incorporate the 2-D excess carrier distribution at the MOS side. This expression is integrated into the LC IGBT model so as to improve the boundary condition. After that, to further improve the accuracy of excess carrier distribution, the number of nodes for the LC IGBT model is increased. Then, the proposed model is verified by comparison with TCAD simulation and experiment result. However, the carrier dynamics during turnoff process still have some errors. Finally, the reason of the error is investigated and the limitation of the quasi-static assumption used in the charge control equation is analyzed.