Recently, the organic polymer films attract attention as promising dielectric films which reduce environmental burdens and inhibit RC-delays. It is very important to understand its mechanical properties. In the previous studies, we could evaluate its reliability by measuring the interfacial energy release rates during the peeling under various conditions. So in this study, we applied this method to several types of specimens. Then, the phase angle effect on interfacial toughness and its contributions were considered by analyzing the results. In addition, we derived fracture criterion in order to feed back to manufacturing process. SiLK (trademark of the Dow Chemical Company) was selected as dielectric material. We prepared two types of specimens. One consists of spin-coated SiLK layer sandwiched between Si substrates using adhesion bond (adhesion bond specimen). The other is made by the following process; at first, two Si substrates with spin-coated SiLK were swelled in solvent. Then, their SiLK faces were pressured and heat cured in oven (thermal pressure bond specimen). Four points bending and DCB tests were performed. Crack path was identified using SEM observation and ESCA analysis in addition to the mechanical test. From the results under different mode mixty condition, the existence of phase angle effect on facial fracture toughness was studied out. Its primary factors were due to bridging of SiLK layer and plastic deformation of SiLK layer and/or adhesion bond layer. Moreover, we evaluated the fracture criteria under several conditions using an ellipse approximation.