Novel Wafer Bevel Treatment for Water Immersion Lithography

In this study, we focus on the controllability of a wafer bevel from adhesion and hydrophobicity viewpoints in order to solve the problems of film peeling and microdroplet formation around wafer bevels, which can result in pattern defects and degrading of the overlay and focus accuracy because of local temperature variation around several sensors due to the vaporization heat of the leaked water. Hexamethyldisilazane (HMDS) treatment is a common solution to these problems. We examine a novel wafer bevel treatment utilizing silane coupling agents (SCa) for obtaining high hydrophobicity and adhesion. These groups react with inorganic substrates and films on the surface that are subjected to a novel chemical treatment (NCT). The coating performance of chemicals on the surface by the NCT and the aging stability of the formulated solution of the SCas are examined for optimizing the composition of the NCT solution. We revealed that the NCT agent, which is comprised of long-chain alkyl type SCa and additive (i.e. acid and salt), has good performance. Furthermore, we verified the superiority of using NCT in the water meniscus stability with high scanning speed (i.e. 500 mm/sec) and water leakage in wafers with a topcoat, ArF resist, and bottom antireflective coating (BARC) using a quasi-immersion exposure stage.