Energy Transfer Characteristics at the Interface between Thin Film and Substrate

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Heat transport characteristic of an interface between thin film and solid has been an attractive problem in both thermal engineering and thermal science. Recent progress of micro-fabrication techniques makes it possible to reduce the size of electric devices or sensors dramatically and this downsizing causes a large heat generation at local areas. Therefore, how to remove the heat generated from hot spots becomes an important problem, in terms of the lifetime and reliability of the devices and also it may be essential for developments of high performance sensors. As heat conduction is the predominant mechanism in microscale heat transfer, thermal boundary resistance between thin film and substrate, R_<bd>, plays an important role in the heat removal process. However, although theoretical models for the resistance in the range of low temperature region, under about 30 K, are developed, the resistance in the room temperature region has not been well examined.For the measurement of the th … More ermal boundary resistance, we usually add a laser heating to a thin film and observe a response of the film temperature. As the response is very quick, usually in the order of micro second, we must adopt a measurement technique with high time resolution. Reflectance thermometry is one of the most suitable technique for it This technique is based on the fact that a reflectivity of films varies with the film temperature. For a calibration of thermo-reflectance coefficients, C_<TR>, we applied the 3 ω method. By comparing the experimental result with time responses of film temperature in heat conduction simulations, we can obtain the value of the thermal boundary resistance.The main results obtained in this research are as follows.(1) The 3 ω method is effective for the measurement of thermo-reflectance coefficients and the coefficients of a gold film and a platinum one on glass substrates are obtained as -4.15x10^<-5> [1/K] and -3.51x10^<-5> [1/K], respectively.(2) The thermal boundary resistances between Pt and Au films and glass substrate are 5.0x10^<-7> [m^2K/W] and 1.0x10^<-6> [m^2K/W], respectively. Less