Study of base additives for use in a single layer 193 nm resist based upon poly(norbornene/maleic anhydride/acrylic acid/tert-butyl acrylate)

Abstract

We report on a study of the chemical and lithographic behavior in a 193 nm single layer resist of two types of base additives, aminosulfonates onium and tetrabutylammonium carboxylate salts. These additives were examined because of their low potential for undesirable reaction with maleic anhydride or acrylic acid repeat units in norbonene/maleic anhydride/acrylate based 193 nm resins. For ammonium carboxylate additives it will be shown that using these gives comparable lithographic performance to a standard formulation containing an amine additive. For aminosulfonate onium salts a study was done of the relationship between chemical structure of these additives and their thermal stability and the lithographic performance imparted by these to a 193 nm single layer resist system. It will be shown that the decomposition temperature is a function of the basicity (nucleophilicity) of the counter anion decreasing with increasing basicity but can be improved by going from an iodonium to a sulfonium chromophore. Cyclamate and cysteate onium salts will be shown to provide good lithographic performance with good post-exposure bake delay latitude.