IMAGING OF PHOTOGENERATED ACID IN A CHEMICALLY AMPLIFIED PHOTORESIST

Chemically amplified photoresists are widely used throughout the semic onductor industry clue to the need for high throughput in the lithogra phy process, Knowledge of the location of acid molecules in chemically amplified resists is of paramount importance for the process control of the image formation of almost all the lithographic techniques used in the semiconductor industry today. We have demonstrated a technique based on pH-dependent fluorescence which can measure directly the spat ial distribution of the photoacid in photoresist films without the nee d of any other subsequent process after exposure. By adding a small am ount of fluorescent material to the resist, a latent image can be form ed when photogenerated acid molecules quench the fluorescence in expos ed areas. We demonstrate images formed after exposure of SAL605 resist films to x-ray radiation, with no post-exposure bake, and show that t he optical contrast is a function of dose. We also show that the same technique can be utilized for rapid evaluation of photoacid generator efficiency. (C) 1998 American Institute of Physics.