Photoreactive fluorinated polyimide protected by tetrahydropyranyl (THP) group based on chemical amplification: Acid generation in polyimide film and lithographic properties

Abstract

AbstractThe photochemistry of photoacid generator (PAG), diphenyliodonium 9,10‐dimethoxyanthracene‐2‐sulfonate (DIAS) and diphenyliodonium 8‐anilinonaphthalene‐1‐sulfonate (DIANS) was investigated in both alkalinesoluble polyimide (6FDA‐AHHFP) and novolak films. The quantum yields of photodissociation of DIAS and DIANS in both 6FDA‐AHHFP and novolak films. The quantum yields of photodissociation of DIAS and DIANS in both 6FDA‐AHHFP and novolak films were determined as 0.11, 0.21, 0.12 and 0.26, respectively. On the other hand, the quantum yields for acid generation from DIAS and DIANS in both of these films were 0.07, 0.18, 0.09 and 0.22, respectively, in the presence of an acid indicator. These results indicate that the values of the quantum yields of photodissociation and photoacid formation for DIAS and DIANS in 6FDA‐AHHFP film are lower than those in novolak film. In order to elucidate the lowering of the quantum yields in 6FDA‐AHHFP film, fluorescence quenchings of sodium 9,10‐dimethoxy‐anthracene‐2‐sulfonate and ammonium 8‐anilinonaphthalene‐1‐sulfonate by a model compound of polyimide was carried out in acetonitrile. The fluorescences of these two salts were efficiently quenched by the model compound with the diffusion‐controlled rate constant in acetonitrile, suggesting that a strong electron‐accepting capability of the imide carbonyl group may hinder the electron transfer process within PAG molecules in 6FDA‐AHHFP film. Although a polyimide (6F‐THP) protected by tetrahydropyranyl group is insoluble in aqueous base, 6F‐THP film containing PAG became soluble in a 2:1 mixture of 2.0 wt% tetramethylammonium hydroxide (TMAH) and methanol by exposure to 365 nm light and successive post‐exposure baking (PEB) at 120°C for 10 min. The sensitivity and contrast of 6F‐THP with DIANS after the PEB conditions mentioned above were 110 mJ/cm2 and 3.7, respectively. A high‐resolution pattern with a good profile was transferred into the 3 μm thickness of the 6F‐THP film.