| Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 95 === Hollow cathode arc (HCA) ion plating system has been developed to deposit hydrogen-free diamond-like carbon (DLC) films and nanocrystalline diamond films free of micro-particles. Then, DLC and diamond films were studied as mold materials or as anti-adhesive layer on silicon molds in imprint lithography technology.
Although hydrogen-free DLC film was usually deposited by filtered cold cathodic arc method, the deposition rate was low and the film contained micro-particles. HCA ion plating was therefore proposed and developed in order to enhance the deposition rate and to eliminate micro- particles. HCA used a graphite tube as the hollow cathode, a graphite-ring as the anode and a graphite shield, which was mounted between the cathode and the anode to avoid arc trigger outside cathode tube. High temperature hollow-cathode was maintained at a temperature higher than 2000 oC by using Ar gas flow and high DC current over 120A to generate high densities of ions. No particle was emitted from the cathodic tube during steady-state operation owing to the shield constricting the arc discharge from the inside of the cathodic tube.
HCA was employed to deposit hydrogen-free DLC film free of micro-particles. The hardness of hydrogen-free DLC film reached to 19 GPa at a deposition temperature of 400oC. DLC film deposited at such a high temperature can rarely exhibits such high hardness.
Nanocrystalline diamond films were also grown by the HCA system with various compositions ratio of Ar /H2 and CH4/Ar /H2. Large-area continuous nanodiamond film can not be obtained using Ar /H2, but continuous nanodiamond film in larger area can be obtained using CH4/Ar /H2. Carbon supply from the graphite cathode tube is not enough, and a carbon source like methane (CH4), is need to deposit continuous nanodiamond film with an average grain size of 10 nm.
DLC and diamond films were also applied to high temperature imprint lithography process anti-adhesive layers of silicon mold. DLC films were deposited by plasma-enhanced chemical vapor deposition (PECVD) onto 4” Si-molds with micro-scale feature less than 5 μm. After hot-embossing process, the pattern of Si-mold was completely transferred to PMMA layer on the flexible PET substrates and the Si substrates. When nanodiamond films were deposited by PECVD, the pattern with micro-feature was also successfully transferred to the substrates at an imprint temperature near Tg of PMMA. Furthermore, the nano-scale patterns were fabricated directly on the DLC films and nanodiamond films as imprint molds by imprint lithography process. The nano-patterns could be successfully transferred into PMMA layer precisely on Si substrates without removing the mold at high temperature.
Finally, the modified reversal imprinting lithography by rolling process was carried out to transfer the patterned polymer layer from the mold with self-assembly monolayer of OTS/DMDS onto the flexible PET substrate. The process has been shown to be capable of transferring any nano-scale pattern features, such as dots, stripes, and tetrahedral pattern, onto the substrate. The thickness of residual layer could be controlled by varying the PMMA concentration and the spin coating speed. The reversal imprint lithography by rolling process is very effective to transfer the large-area patterns onto the substrate with high producibility and reliability.
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