Improvement of the durability of crosslinked PTFE molds for UV- /EB-nanoimprint lithography

It has been reported that the nano- /micro- fabricated crosslinked polytetrafluoroethylene (RX-PTFE) by focused ion beam (FIB) direct etching technique could be used as the polymeric molds for the ultraviolet nanoimprint lithography (UV-NIL) and electron beam NIL (EB-NIL). In this study, to evaluate the durability of RX-PTFE molds for repeating printing cycles, the RX-PTFE was spin-coated on two kinds of substrates; none-metal treated silicon wafer and 50 nm thick Al-layer deposited one. Then, RX-PTFE molds were obtained by FIB irradiation. 450 × 450 nm and 950 × 950 nm squares and Φ 1000 nm circle were fabricated in 40 × 40 μm areas. Intervals of the squares and circle were 450 nm, 950 nm and 1000 nm, respectively. In the case of none-treated substrate, the 3 ^rd imprinted pattern was distorted. On the other hand, the 10 ^th imprinted patterns with UV-NIL were successfully obtained with the Al-layer deposited substrate. Though it is concerned about the mechanical strength of RX-PTFE degrading due to EB irradiation, EB-NIL was similarly succeeded with Al-layer deposited substrate. It is considered that the mold durability for printing would be improved due to high adhesion between Al-layer and RX-PTFE, because the fluorination of Al was caused by crosslinking treatment at high temperatures. Thus, it is suggested that the durability of RX-PTFE mold with Al-layer deposited substrate would be retained after 10 times UV- /EB-NIL processes.