Progress in unzipping polyaldehyde resist systems

In addition to the high sensitivity, the use of photochemically generated acid as catalytic species has provided a basis for designing an entire family of advanced resist systems. The original chemical amplification scheme utilized 1) crosslinking through cationic ring-opening polymerization of pendant epoxide groups, 2) acid-catalyzed deprotection of polymer pendant groups to change the polarity for dual tone imaging, and 3) acid-catalyzed depolymerization of polyphthalaldehyde (PPA) to provide a self-developing positive resist (4). Each one of these design concepts has made a significant progress. This paper reports a recent progress in the positive PPA resist systems.