Preparation And Photopatterning Of Malonic Bis-pyrene Ester Copolymer LB Films

The continuing drive toward higher circuit density in microelectronic devices has motivated research efforts in variety of high-resolution techniques. So it is necessary for the development of large-scale integrated circuit to develop highly sensitive resist materials system and appropriate film-forming methods. In order to meet the continuing demand for smaller feature size and greater circuit density, this thesis employs deep ultraviolet (DUV) as light source, Langmuir-Blodgett (LB) film technology as means of photoresist film, we designed and synthesized a series of novel pyrene malonate ester. Its film properties, lithography properties and Photolysis mechanism were studied.1. A series of copolymers [N-alkylmethacrylamide-co-Allyl-malonic acid-dipyrene ester] were synthesized [Fig.1]. The composition and molecular weight of these copolymers were characterized by 1H NMR and gel permeation chromatography (GPC), respectively.2. The monolayer behavior on air/water interface and Langmuir film transfer ability of copolymers were determined byπ-A isotherms and UV spectra. The copolymer containing high mole fraction of hexadecyl group could form condensed monolayer on air/water interface and can be transferred to different solid supports to form homogeneous LB films. For example, the linear relationship between the absorbance and the number of deposited layers of p(HDMA-DPyMAMA) (b2) shown in Fig2, the fluorescence micrograph in Fig3 and AFM 3-D images in Fig4 suggested that a regular deposition of the copolymer monolayer took place, resulting in uniform b2 LB films. Fig2 UV absorption of p(HDMA-DPyMAMA)[b2] LB films deposited on quartz (Inset:plots of the absorbance at 196 nm,278 nm and 346 nm vs. the numberof LB films deposited). Fig3 Fluorescence micrograph of 101 layers ofp(HDMA-DPyMAMA30) [b2] LB films on silicon. Fig4 AFM 3-D images of p(HDMA-DPyMAMA30) [b2] LB films on LB films with one layer on silicon.3. The 41 layers of b2 (copolymer of N-hexadecylmethacrylamide and DPyMAMA, mole fraction of AMDN:14.32%) LB films. LB films patterns with the resolution of 0.75μm could be obtained by deep UV irradiation followed by development with I2/NH4I/C2H5OH/H2O solution, which is used as developping solution as well as etching solvent for the first time. We can both save money as well as reduce the pollution in this way (Fig.5).Fig.5 Optical micrograph of 41 layers p(HDMA-DPyMAMA) [b2] LB films patterns on silicon plate. Figure 6 Optical micrograph of etched pattern of gold films on glass substrateThe pattern with the resolution of 0.75μm could also be transferred to gold film using LB films pattern as resist layer(as shown in Fig 6).4. The photodecomposition mechanisms of b2 LB films irradiated by deep UV were also investigated. The results showed that the copolymer is sensitive to 248nm source(Fig.7) Fig.7 The change of UV spectra of b2 LB films deposited on quartz irradiated by deep UV light:(a) absorption within 190-200nm; (b) absorption within 200-400nmWe speculated that pyrene group in p(HMA-DPyMAMA) polymer changed in photochemical decomposite into phenanthrene or other depending on the wavelength of the 248 nm UV light at the first, and then decomposition of pyrene group or formed other conjugate structure, leading to the formation of carboxylic acid groups. Upon irradiation on the copolymer containing HDMA and DPyMAMA with the light at 248 nm, the p(HDMA-DPyMAMA) LB films exposed to deep UV light could dissolve in water partly and form a position-tone pattern with the resolution of 0.5-0.75μm, and it also showed higher resistance ability in the process of etching gold film. Fig8 is speculated mechanism of b2.Fig.8 Photoreactions of b2 polymer by UV light irradiation...