A positive-working alkaline developable photoresist based on partially tert-Boc-protected calix[4]resorcinarene and a photoacid generator

A positive working low-molecular-weight photoresist based on partially t-Boc protected tetra-C-methylcalix[4]resorcinarene (t-Boc C-4-R) and a photoacid generator (PAG), diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS) has been developed. t-Boc C-4-Rs were prepared by the reaction of C-4-R with di-tert-butyl dicarbonate in the presence of 4-dimethylaminopyridine (DMAP). A clear film cast from a 20 wt% t-Boc C-4-R solution in cyclohexanone showed high transparency to UV above 300 nm. The appropriate t-Boc protecting ratio was about 60 mol% in view of adhesion, deprotection temperature and dissolution rate. The photoresist consisting of 60 mol% t-Boc C-4-R (95 wt%) and DIAS (5 wt%) showed a sensitivity of 13 mJ cm−2 and a contrast of 12.6 when it was exposed to 365 nm light and postbaked at 105 °C for 90 s, followed by developing with a 2.38 wt% aqueous tetramethylammonium hydroxide (TMAH) solution at room temperature. A fine positive image featuring 1.5 µm of minimum line and space patterns was observed on the film of the photoresist exposed to 40 mJ cm−2 of UV-light at 365 nm by the contact mode.