Nonswelling Negative Resists Incorporating Chemical Amplification

Photoinduced crosslinking of polymers through electrophilic aromatic substitution has been achieved with a family of styrenic polymers or copolymers containing both latent electrophiles and activated aromatic groups. These polymers can be used in combination with a photoacid generator to design a non-swelling negative multipurpose resist which can be used for deep-UV, X-ray or E-beam imaging and has a very high sensitivity. For example, in the deep-UV, sensitivities of less than 1 mJ/cm2 are obtained with very high contrasts. Irradiation of the two-component resists results in the generation of strong acid which, upon baking, activates the latent electrophile to a carbocationic species that couples to neighboring activated aromatic moieties in a crosslinking process. Vinyl-phenol units are incorporated in the copolymer formulation to provide activated aromatic sites, solubility of the resist in aqueous base, and lack of swelling during image development. Alternate three-component formulations in which the latent electrophile is separate from the activated aromatic moiety are also suitable.