Studies On Preparation And Application Of Polymer Langmuir-Blodgett (LB) Films

Copolymers [N-alkyl(meth)acrylamide-co-4-tert-butylphenol methacrylate, p(NAA-BPhMA)] were synthesized. The composition and molecular weight of these copolymers were characterized by ~1H NMR and gel permeation chromatography (GPC), respectively.The monolayer behavior on air/water interface and Langmuir film transfer ability of copolymers were determined by the length of alkyl in acrylamide and the mole fraction of BPhMA in copolymers. The copolymer containing hexadecyl group and low mole fraction of BPhMA could form condensed monolayer on air/water interface, and be transferred to different solid supports to form homogeneous LB films.The 2c(3) (copolymer of N-hexadecylmethacrylamide and BPhMA, mole fraction of BPhMA: 30%) LB films and 2d(4) (copolymer of N-hexadecylacrylamide and BPhMA, mole fraction of BPhMA: 20%) LB films patterns with the resolution of 0.75μm could be obtained by deep UV irradiation followed by development with acetone. The resolution of 2d(4) LB films pattern could reach to 0.5μm.The photodecomposition mechanisms of 2c(3) and 2d(4) LB films irradiated by deep UV were also investigated. The decomposition of side chain and the cleavage of main chain of 2c(3) occurred almost at the same time. However, the scission of 2d(4) had two steps: carbonyl group of BPhMA decomposed immediately after irradiation; then the cleavage of main chain occurred.The pattern with the resolution of 0.5-0.7μm could be transferred to gold and copper film using LB films pattern as resist layer. The patterns were detected with AFM method, the results show that the diffraction of UV light occurred in the process of photopatteming due to the unsatisfactory contact between LB films surface and photomask. The thickness of LB films was decreased after development because the regions covered by photomask were also irradiated slightly by UV light. Apparently, the diffraction affected the pattern transformation, especially on the patterns with higher resolution. According to the thickness of LB films, the arrangement of molecules in 2d(4) LB films was more condenced than that in 2c(3) LB films. Moreover, the resist ability of 2c(3) LB films was better than that of 2d(4) LB films under the same condition.2d(4) LB films had higher resolution than 2c(3) LB films, but the former was difficult to be applied because of its insensitivity. On the other hand, 2c(3) LB films were sensitive to UV light and had good resistance against enchants in different chemical conditions. These properties of 2c(3) LB films are expected to be applicable to a nano-photoresit for 250 nm UV photolithography.