A new positive-type photoresist based on mono-substituted hydroquinone calix[8]arene and diazonaphthoquinone

Abstract

Mono-substituted hydroquinone calix[8]arenes 1a and 1b were synthesized by the debenzylation of O-substituted p-benzyloxyphenol calix[8]arenes which were prepared by the cyclization of p-benzyloxyphenol and paraformaldehyde in the presence of a base, followed by acylation with acetic anhydride or toluene-p-sulfonyl chloride. The calixarenes provide highly transparent films from their solutions in ethyl lactate (EL). A new positive-type photoresist based on the calix[8]arene 1b having toluene-p-sulfonate groups as a base-developable matrix and diazonaphthoquinone-4-sulfonate [DNQ(4)] or -5-sulfonate [DNQ(5)] as a photoreactive dissolution inhibitor has been successfully developed. The difference of dissolution rates for this resist system toward 1.5 wt% aqueous tetramethylammonium hydroxide (TMAH) solution reached 1300-5000 times before and after UV radiation (200 mJ cm ^–2 ). Thus, the photoresists containing 25 wt% of DNQs showed high sensitivities of 30-37 mJ cm ^–2 (D) and contrasts of 2.5-2.8 (γ) when they were exposed to 365 nm light and post-exposure baked (PEB) at 100 °C for 90 s, followed by developing with 1.5 wt% aqueous tetramethylammonium hydroxide (TMAH) solution at room temperature. A fine positive image featuring 1 µm of minimum line and space patterns was also printed on the film which was exposed to 40 mJ cm ^–2 by the contact mode.