Measurement of Thermal Conductivity and Interface Thermal Resistance of Multilayered Thin-Films Using Variable Pulse-Width Transient Thermoreflectance

This work discusses the use of a non-contact, non-invasive and in-situ measurement approach for determining the thermal conductivity of thin films used in the microelectronics industry, along with the interface thermal resistance between the films. The approach is based on the thermoreflectance method, where the change in the surface temperature is measured by detecting the change in the reflectivity of the sample. The results presented in this paper show that by using different pulse-widths for the heating laser, as well as a variable wavelength for the probing laser, the proposed method enables the measurement of several unknown parameters in a multi layered sample, which is representative of modern devices developed by the microelectronics industry. In addition, it is shown that the method can be further improved to minimize the measurement uncertainties by estimating a-priori the optimum thickness of the metal absorption layer that needs to be used. A property called responsivity is described, and it is shown that maximizing its value is indeed producing the lowest measurement uncertainties. An objective of this work is to provide guidance to investigators building similar systems and help others improve existing systems.