Gerhard Buhr

Image Reversal Resist for g-line Exposure: Chemistry and Lithographic Evaluation

Fundamentals and mechanism of a direct image reversal process, which switches the tone of a resist from positive to negative without added bases are presented. A sulfonic acid generated photochemically from an aryl naphthoquinonediazide-sulfonate catalyzes the crosslinking of exposed resist areas. Based on this principle, a concept for a new naphthoquinonediazide with sufficient absorptivity at g-line and preserved acid generating capability was developed. The desired functionality of the PAC, prepared in a multistep synthesis, is proven. Guidelines for optimization of the most important process parameters are established for the newly formulated g-line image reversal resist. Lithographic results include 0.6 μm equal lines and spaces with nearly vertical side walls using a 0.35 NA g-line stepper.