Control of parameters influencing the thermal imprint of parylene/silicon

The study aims to investigate the possible defects that may occur during imprinting of poly(chloro-p-xylylene) (parylene-C) film (thermal oxidation, delamination, thermal cracking and insufficient filling at the periphery) and to overcome them by modifying the process conditions and mold design. X-ray diffraction (XRD) analyses results for the parylene-C films indicated that higher deposition pressure leads to a lower crystallinity of parylene-C film. By tuning the process conditions and mold design, patterned fields (composed of arrays of 25-μm-high, 10-μm-wide and 1-mm-long lines with 10 urn spacing) in 0.4-mm-thick and 20-mm-sized nickel molds could be successfully replicated on 60-μm-thick parylene-C films deposited at both 25 and 45 mTorr. Complete filling over the whole imprint area could be achieved at <270°C with the press force at 2kN and the press hold time of 900 s with the aid of an implemented dummy pattern. Both thermal cracking and delamination could be avoided, even at 270°C, under the established process conditions and mold design with the help of an adhesion promotion treatment of silicon substrates (SF₆ plasma etching for 2 min and spin-coating of KBM-503-based solution). Furthermore, the molds used for paryelne imprinting could be cleaned by dipping in chloronaphthalene solution at > 175°C, followed by an oxygen plasma etching.