Laser Thermoreflectance Measurement for Evaluating Heat Capacity and Interface Heat Resistance of Low-k Films

Abstract

A novel technique that combines laser thermoreflectance measurement with the 3-omega method is proposed for evaluating the heat capacity of low-k films and the heat resistance at the interface between the low-k film and Si substrate. It was demonstrated that the heat capacity of thin films and the heat resistance at the interface can be determined by obtaining the heat effusivity of the film from laser thermoreflectance measurements, the total heat resistance obtained with the 3-omerga method, and the film density and thickness found from x-ray reflectivity measurements. The heat capacity of SiOC films was determined to be C_p(SiOC) =1.1 kJ/kgK with interface heat resistance of R_int(SiOC) = -2.37×10⁻⁸ m²k/W, while the heat capacity of Th-ox films was determined to be C_p(Th−ox) =0.61 kJ/kgK with R_int(Th−ox) = +1.74×10⁻⁸ m²k/W. A DSC heat capacity measurement confirmed the reliability of the evaluated C_p data. XRR and TEM examinations revealed that the negative interface heat resistance exhibited by the SiOC films originated from a high density layer at the interface between the film and Si substrate; and the positive interface heat resistance displayed by the Th-ox films stemmed from atomic defects at the interface between the film and Si substrate. These results confirmed that this method is a reliable and effective method for evaluating the heat capacity of low-k films and the heat resistance at the interface.