Measurement of the Temperature Dependence of the Piezoresistive Coefficients of 4H Silicon Carbide

Piezoresistive stress sensors on silicon were developed for measuring in-situ stresses in electronic packages, but due to its relatively low bandgap energy, the upper temperature range of silicon is limited. Stress sensors made with wide bandgap semiconductors such as 4H silicon carbide (4H-SiC) offer the advantage of much higher temperature operation [1] and can be utilized to monitor stresses in high-voltage, high-power SiC devices. The piezoresistive behavior of such sensors is characterized by piezoresistive (pi) coefficients, which must be calibrated before the stress measurement. In the prior study [2], the piezoresistive coefficients of 4H-SiC were calibrated only at room temperature, but 4H-SiC tends to be operated at high temperature. Thus, the piezoresistive coefficients under different temperatures are required.This work focuses on experimental study of the piezoresistive coefficients at different temperatures, from 300k to 450k. Calibration has been performed using four-point bending method with strip on flex circuit [3] specimen. A special four-point bending apparatus integrated into an environmental chamber is utilized.