On-Chip Sensor Substrate Requirements for Accurate Junction Temperature Measurements

Abstract:
On-chip sensors are a promising way to monitor the junction temperature of power semiconductors. However, the sensor material, dimensions, and location, can impact the measured temperature. This paper assesses the accuracy and time response of an on-chip sensor according to its substrate thermal conductivity. Results are presented from Finite Element Simulations. It is found that for steady-state temperature measurements, the thermal conductivity of the substrate does not significantly impact the measured temperature. For example, from 10 W/mK to 200 W/mK substrate thermal conductivity, the temperature on the sensor surface remains within 0.01deg C. On the other hand, for transient measurements at frequencies as low as 1 Hz, the impact of the sensor thermal conductivity is apparent.