Theoretical Study of Latent Image Formation in Chemically Amplified Resists

Theoretical analysis of chemically amplified resists indicates that a higher reaction order of acid-catalyzed reaction and lower diffusion length of acid enhance image quality. We identified the relation between diffusion length and the number of catalytic acids appropriate for inducing a given amount of acid-catalyzed reactions as a function of the difference between the activation energies of diffusion (E ad) and acid-catalyzed reaction (E ar), and the post-exposure baking (PEB) temperature. When E ad=E ar, the diffusion length required for a certain amount of acid-catalyzed reaction is inversely proportional to the square root of the amount of generated acids, regardless of PEB temperature. When E ad≠E ar, the required diffusion length depends on PEB temperature. When E ad<E ar, the diffusion length is smaller at higher PEB temperatures, and this will be preferable for enhancing the resist resolution.