Application Of The 3-omega Method On Measuring The Interfacial Thermal Resistance In Thin Films

With the miniaturization of electrical devices, the problem caused by heating effect has made increasing the thermal conductivity（TC） and decreasing the interfacial thermal resistance the critical factor to improve the reliability of thin film devices. The overheating of electrical devices may lead to serious performance degradation or even a risk failure in electrical materials. Therefore, a characterization of material’s thermal properties is of great importance to the design and manufacture of electrical devices. As the microelectronic devices have been extensively used and gained more importance in national economy, it is very important to study the thermal characterize method for thin film materials used for microelectronic industry. Through this research, we could obtain more precious and comprehensive thermal physical data of thin films.D. G. Cahill has built a brand new thermal physical property characterization method based on a way of harmonics detection, which was named the 3ω method. After many years of development, this 3ω method has become a very popular way to characterize thermal properties because of its simplicity and high efficiency, and has been used to measure the bulk and thin film’s thermal conductivities of different dielectric materials. However, the 3ω method also has its own shortcomings, as it is mainly restricted to characterize the thermal conductivity of thin films. On the other hand, another parameter, the interfacial thermal resistance（ITR） is also critical in thin film’s heat-conducting measurement. Thus, it is vital to expand the harmonics-based 3ω method to characterize the ITR of thin films, and use it to serve for aerospace, detection, material, energy conversion and building field.As a widely used material in electronic ceramic industries, Barium Titanate（BaTiO₃, BTO） belongs to a typical perovskites ferroelectric oxide, and owns great dielectric, ferroelectric and piezoelectric properties. Using the 3ω method to make a systematic research on BTO thin films is rather helpful for an advanced use of BTO films in electronic industries.During our research, we set up a mature and easy-to-use testing system containing a lock-in amplifier and a bridge circuit based on the 3ω method to measure the TC of SiO₂ films with 5 different thicknesses prepared by dry-oxygen oxidation method, and we then used this measuring system to calculate the ITR between SiO₂ films and Si substrate according to the thermal resistance formula. By compared the measuring results with the results reported in literature, we could confirm the reliability of this measuring system. Next, deposited different thickness of barium titanate（BTO） thin films with different layers on SiO₂ films using the polymer-assisted deposition method（PAD method） which annealing under hydrogen atmosphere. Then we measured the BTO/SiO₂ multilayer thin film’s TC by the 3ω system. Using the relationship between TC and ITR, thus we could determine the BTO film’s TC and calculate the ITR between BTO and SiO₂ films. Through our work in this paper, the result showed that the TC of BTO films prepared by PAD method is 5.56 W/m K, and the ITR of BTO/SiO₂ is 2.02×10-8 m2W/K. The estimating uncertainty of measured TC and ITR is about 15% and 12%.