Factors affecting photosensitivity enhancement of chemically amplified photoresists by an acid amplifier

The acid proliferation reaction of tert-butyl 2-methyl-2-(tosyloxymethyl)acetoacetate to liberate the corresponding sulfonic acid by the action of a tiny amount of photogenerated acid was investigated in positive- and negative-working chemically amplified photoresists. The addition of the acetoacetate as an acid amplifier to the photoresists resulted in a marked improvement in contrast, while the level of photosensitivity enhancement was relatively small for both types of photoresists, showing that the inconspicuous enhancement of photosensitivity is due to the suppression of the diffusion of acidic species in polymer films. The marked improvement of photosensitivity was achieved by the fabrication of novel double-layered photoresists doped with the acid amplifier.