Acid proliferation processes of 3-phenyl-3,3-ethylenedioxypropyl sulfonates in photosensitive polymer films leading to "air infection"

The thickness of UV-irradiated Films of poly[p-(tert-butoxycarbonyloxy)styr ene] and poly(tert-butyl methacrylate) containing a photoacid generator as a chemically amplified photoresist was reduced by the deprotection of the s ide chain residues as a result of the acidolysis reaction catalyzed by a ph otogenerated acidic species. It was observed that the reduction of film thi ckness is spread laterally on a millimeter scale to unexposed areas upon he ating in the presence of 3-phenyl-3,3-ethylenedioxy-1-propyl p-toluenesulfo nate as an acid amplifier that displays the autocatalytic acidolysis referr ed to as acid proliferation. The enlargement of areas showing the thickness reduction was suppressed effectively by covering the films with a glass pl ate or a polymer film. This observation suggested that the acidolysis react ion of the films is caused predominantly by the migration of acid molecules originated from the acid amplifier through the air. This was confirmed by the transfer of acid molecules to another acid-sensitive polymer layer plac ed an the acid-generating film through an air gap. The photosensitivity enh ancement of the chemically amplified photoresists owing to the acid prolife ration is discussed on the basis of these results.