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 multifunctional bisphenolAbased epoxies which are polymerized using cationic aryl sulfonium hexafluoroantimonate. Surface characterization via X-ray photoelectron spectroscopy and contact-angle titration reveals that baking the dielectric yields nucleophilic sulfur substitution of hydroxylated surface species to produce a diphenyl sulfoxide reaction product. Such reactivity provides a convenient means of altering the dielectric surface acidity. Surface acidity is shown to be well correlated to the adsorption of a high molecular weight cationic polyacrylamide deposited from solution during microelectronics fabrication.