Interfacial-shear strength of the perfluorocyclobutane films on silicon

The debonding behavior of perfluorocyclobutane (PFCB) films on silicon (Si) has been investioated using Vickers indentation as a function of cure temperature and film thickness. PFCB films on Si were processed by spin coating (1-4 mu m) and solution casting (20-60 mu m). The interfacial shear strength of solution-cast PFCB films was independent of film thickness. The interfacial shear strength increased with cure temperature. The PFCB/Si cured at 225 degrees C exhibited interfacial shear strength of 123 MPa, and the strength increased to 163 MPa when the cure temperature was raised to 275 degrees C. The increase in interfacial-shear strength with temperature has been attributed to the increase in the density of bonds between PFCB and Si due to an increase in the density of crosslinks. Spin-coated films exhibited cracking due to the penetration of the indenter into the substrate, and the extent of cracking increased with the load.