Thermally induced intramolecular surface reactions on a photoimageable dielectric

The effect of bake temperature on the surface chemistry of a photoimageable dielectric is investigated. The dielectric contains mixtures of multifunct ional bisphenol A based epoxies which are polymerized using cationic aryl s ulfonium hexafluoroantimonate. Surface characterization via X-ray photoelec tron spectroscopy and contact-angle titration reveals that baking the diele ctric yields nucleophilic sulfur substitution of hydroxylated surface speci es to produce a diphenyl sulfoxide reaction product. Such reactivity provid es a convenient means of altering the dielectric surface acidity. Surface a cidity is shown to be well correlated to the adsorption of a high molecular weight cationic polyacrylamide deposited from solution during microelectro nics fabrication.