The use of surface modifiers to mitigate pattern collapse in thin film lithography

It has become clear that although line edge roughness and resolution are important for future lithographic technology nodes, other issues such as pattern collapse must be addressed as well. One of the primary modes of pattern collapse is pattern collapse caused by loss of adhesion of the resist from the substrate. The main forces which govern pattern collapse by adhesion failure are related to substrate/resist interactions. Though several methodologies to improve pattern collapse have been investigated, such as the use of surfactants during the final rinse, the use of such methods virtually all suffer from some serious drawback. To this end, we have developed a reactive surface modifier capable of covalently attaching to a positive tone resists containing hydroxystyrene groups. A vinyl-ether-modified silane was prepared and effectively applied using a solution silanization reaction. A hydroxystyrene-based positive tone copolymer resist was applied and subjected to a post apply bake to allow sufficient time for reaction with the surface modifier to occur prior to patterning using e-beam lithography. Ultimately, it was determined that covalent attachment of the surface modifier to the photoresist during the post apply bake resulted in enhanced resist/substrate adhesion of photoresist lines as evidenced by improved pattern collapse performance in high resolution imaging experiments.