Modulation method for measuring thermal impedance components of semiconductor devices

The paper describes the modulation method of measuring the thermal impedance of semiconductor devices as well as its implementation. In contrast to the standard method (JESD51-1 standard) which requires heating the device under test by the stepped power, the modulation method uses heating power modulated harmonically. A pulse sequence of heating current, with the pulse length varying harmonically, is passed through the device under test. The p-n junction temperature is measured through a temperature-sensitive parameter, namely a forward voltage drop on the p-n junction between heating pulses at low measuring current. First harmonic of the p-n junction temperature oscillation is determined by the discrete Fourier transform, which allows to determine thermal impedance absolute value and phase at modulation frequency of heating power. An analysis of the dependence of thermal impedance on modulation frequency allows to determine thermal impedance components corresponding to the structural elements of the device under test. Numerical simulation shows that the thermal resistance components on the Foster's network may be determined at the modulation frequencies corresponding to the first derivative minima of the thermal impedance of the real part of frequency dependence. The main characteristics of the device that implements the method are described.