Investigation of the usage of a chip integrated sensor to determine junction temperature during power cycling tests

摘要

For an exact qualification of power semiconductor devices' power cycling withstand capability it is crucial to determine the junction temperature T_j as quickly and accurately as possible. State of the art is to measure T_j of silicon (Si) IGBTs indirectly by the V_(CE)(T)-method, using the dependence of saturation voltage V_(CE) on temperature at low measurement current. This method however is not applicable to silicon carbide (SiC) transistors. The purpose of this work is to evaluate a direct measurement of T_j in a power cycling test bench using a temperature sensor integrated in the transistor, i.e., a string of small diodes placed centrally in the chip. For validation, measurements taken with the sensors are compared to those gained with the conventional V_(CE)(T)-method and simulation results. For this purpose Si IGBTs equipped with temperature sensors are evaluated. The comparison displays a good and physically plausible correlation between the T_j measurement by a sensor and the well established V_(CE)(T)-method, which qualifies the sensor based measurement for application in power cycling; this is in particular important to expose SiC MOSFETs with anti-parallel SiC Schottky diodes to power cycling tests, where standard methods to measure T_j are not applicable. Consequently first measurements of T_j in such modules in a power cycling test are shown as well.