Analytical Prediction of the Thermal Behavior of Semiconductor Power Devices from Room-Temperature I–V Measurements

Abstract

The thermal characterization of power devices is an inevitable task in the industry. Thermal transient testing is one of the major tools for this characterization, as it is not only capable of giving information about the actual thermal parameters but may also reveal the root cause of potential device failures. The testing may occur on single packages or modules on a dedicated standard test bench, or “in situ”, in an actual assembly. The testing process itself is very fast in both cases, on the order of seconds, but the transient measurement needs to be preceded by a calibration step to determine the temperature dependence of a temperature-sensitive parameter (TSP) of the semiconductor device. This may require a long time, as the device has to be measured at many stabilized temperatures, which in the case of power devices may take hours. It also has to be considered that, especially in “in situ” measurements, reaching the highest device temperatures of power devices may even damage other parts of the surrounding electronics. Moreover, the temperature distribution inside a module will be different at calibration time than during operation with the same junction temperature, as bond wires and copper traces do not reach the chip temperature in the latter case. This paper presents a methodology that can be used to replace the lengthy measurement of one parameter at many temperatures with a fast single I–V characteristics measurement at room temperature. Physics-based calculations assign a unique temperature-sensitive parameter to each item of interest in the system. After the presentation of the theoretical background, the usability of the method is demonstrated by verifying measurements on silicon power devices.

Keywords

• thermal transient measurement
• temperature sensitive parameters
• temperature-to-voltage mapping
• forward voltage
• pn junction