Controlling kinetics of heterogeneous sol–gel solution for high-performance adhesive hybrid films

Abstract

The strength of bonding at epoxy/SiO2 interface and its susceptibility to environmental degradation have profound impact on the lifetime and reliability of microelectronic devices. The incorporation of hybrid film at epoxy/SiO2 interfaces has been shown to alleviate this challenge, but the working time to produce these highly-adherent hybrid films on silicon has been limited to ~10 min. In this work we demonstrate that, by lowering sol–gel aging temperature to 5 °C, the processing window for producing highly-adherent hybrid films on silicon can be extended to more than 6 h. In addition to the extended processing time, an Arrhenius type relationship between sol–gel aging temperature and the optimal sol–gel aging time was observed, with an overall sol–gel reaction activation energy of approximately 2.03 eV/atom that includes both hydrolysis and polycondensation. The enhanced interfacial adhesion was explained in terms of the graded hybrid film structure as determined by X-ray photoelectron spectroscopy depth profiling. The work has significant implications for the successful integration of hybrid film strategy in device packaging technologies. Fracture energy of epoxy/hybrid-film/SiO2 structures with films prepared at different sol–gel aging times and temperatures. Black, red and blue curves show fracture energy as a function of sol-gel aging time for solutions aged at 25, 15 and 5 °C respectively. Grey dashed line indicates Gc = 60 J/m2 while orange dot-dash line represents the adhesion of epoxy/SiO2 interface in the absence of the hybrid film.