Image reversal techniques with a water-based chemical amplified photoresist

A water-based chemical amplified photoresist, which is composed of Novolak resin, hexamethoxylmethyl melamine (HMMM), diphenyliodonium salt and photos ensitizer was investigated. It was found that the diphenyliodonium salt can act not only as the photosensitive acid generator, but also as the dissolu tion inhibitor. As a photosensitive acid generator, the diphenyliodonium sa lt can generate acid after exposure, which catalyzes the condensation of No volac-HMMM system in post-exposure bake step. Using the alkali-ethanol aque ous solution as the developer the photoresist can be of negative tone. As a dissolution inhibitor, the diphenyliodonium salt can prevent the unexposur e film from being dissolved in the developer. Therefore, using the dilute a lkali aqueous solution as developer this photoresist can be of positive ton e. Image reversal can be achieved by selecting different developer and diff erent photographic process. The negative tone image and the positive tone i mage were obtained by the optimized photolithographic parameters.