Simulation based method to eliminate the effect of electrical transients from thermal transient measurements

Thermal transient testing is the industry de-facto test method for the identification of junction temperatures and structural defects inside semiconductor devices. Unfortunately, at the beginning of the thermal transient curve in each case an electric effect can be observed, which appears immediately as the unit power step takes place. This electric effect covers the initial phase of thermal transient, and without knowing it the exact temperature of the device cannot be determined. The current industrial methods make a simple correction by cutting the first stage of the thermal measurement, but it is inaccurate, and the correction requires a manual step, therefore it is uncertain. This article describes a methodology to accurately reproduce the thermal transient curve eliminating the effect of the initial electric transients. We approached the problem by using the combination of thermal transient simulation and measurements, fitting the simulated results to the measured curve knowing that the second half of the measured curve certainly reflects the reality.