A two-step in situ measurement method for temperature and thermal stress of power device based on a single Raman peak

Abstract

Temperature and thermal stress are primary factors leading to the performance failure of power devices. Thus, simultaneously determining the temperature and stress variation of the working devices has become the premise of revealing the failure mechanism. However, the existing methods are still unsatisfactory for in-situ temperature-stress decoupling measurement. To solve this problem, a two-step decoupling method based on a single Raman peak is proposed. In the calibration step, the effective temperature - Raman shift coefficients at different positions of the power devices were measured in the OFF state, and the contribution ratio of temperature and thermal stress to the single peak shift can be determined by analyzing the difference of effective temperature - Raman shift coefficients with intrinsic temperature - Raman shift coefficient. In the in-situ measurement step, the temperature rise and thermal stress variation can be calculated based on the Raman peak shift of the target semiconductor layer and the calibrated contribution ratio. A measurement of the GaN high electron mobility transistor was used to further illustrate the advantages of the proposed method. Compared with the previous multi-peak decoupling method, the temperature and thermal stress distributions of the working device obtained by the two-step decoupling method make more physical sense, and the measurement uncertainty of temperature and stress can be reduced to 1/4 and 1/3 of the previous method respectively. The consistency with the thermo-stress simulation further verifies the reliability and accuracy of the proposed method.