The effects of interface chemistry and alternating mechanical loads on subcritical debonding of thin polymer layers from inorganic dielectrics are of significant interest for the integrity of devices used in a range of modern technologies. However, the mechanisms of subcritical debond growth at polymer interfaces, particularly under cyclic loads, are not well understood. Such subcritical debonding of a representative polymer dielectric (benzocyclobutene) to a silica-passivated silicon substrate was studied under cyclic and monotonic loading in moist environments. The effect of interface chemistry on subcritical debonding was evaluated using selected amino- and vinyl-functional silane adhesion promoters. Debond growth rates over the range of 10~(-3)-10~(-9) m/s were characterized under Mode I and mixed Mode I/Mode II loading. AFM and XPS results suggest that the failure mode of the BCB was cohesive in a region very close to the interface. Fatigue loading was found to significantly accelerate subcritical debond growth rates, producing fatigue striations with a striation height of approx 1-2 nm and a spacing that was correlated with the debond growth rate. A model is presented for the mechanism of striation formation.
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