Dissolution Kinetics near Bottom Interface of a Poly(4-hydroxystyrene-co-(methyl methacrylate)-co-(methacrylic acid)) Film in Tetraalkylammonium Hydroxide Aqueous Developers

Bridging at the bottom of photoresist lines is a major concern in advanced lithography for manufacturing semiconductors. Although the dissolution kinetics near the bottom interfaces of resist films are believed to play a critical role in the generation of bridges, the detailed mechanism remains unknown. In this study, we investigated the dissolution kinetics of a poly(4-hydroxystyrene-co-(methyl methacrylate)-co-(methacrylic acid)) film with underlayers in three tetraalkylammonium hydroxide aqueous developers: tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. The dissolution kinetics near the bottom interface varied with underlayer and the type of developer. This phenomenon was related to the surface free energies of the underlayers and photoresist films and the surface tensions of the developers. In the well-matched case between the underlayers and the photoresists, a thick transient swelling layer containing a significant amount of developer was formed near the underlayer. In the ill-matched case, the transient swelling layer was thin.