Journal of Vacuum Science & Technology B, Vol.28, No.5, 921-925, 2010
Micro- and nanopatterned polymethylmethacrylate layers on plastic poly(ethylene terephthalate) substrates by modified roller-reversal imprint process
In this article, the modified roller-reversal imprint lithography was carried out to transfer patterned polymethylmethacrylate (PMMA) layers from hard molds to plastic poly(ethylene terephthalate) (PET) substrates. The merit of reversal-imprinting is its high flexibility, while the roller's manipulation benefits the throughput. It is evident that this process is capable of transferring any patterns with micro- or nanoscale features such as dots, stripes, and pyramids. The process can be divided into several steps, in sequence, including surface modification of hard molds for PMMA coating, O(2) plasma treatment of PET substrates for robust transfer, and final roller-reversal-imprinting. To increase the mold surface energy, alkyl benzoic acids (surfactants) with different alkyl chain lengths have been exploited to modify the mold surface pretreated with octadecyl trichlorosilane (OTS) solutions, and the influence on the water contact angle of molds was analyzed. The results exhibited that shorter alkyl chain is more effective in decreasing the water contact angle. It can be attributed to the denser arrangement of shorter chains. Overall, complete and continuous PMMA films can only be obtained on surfactant-treated OTS-molds. On the other hand, the water contact angle on PET substrate is more easily decreased at low pressure plasma treatment. However, for the sake of rapid and simple process, atmospheric plasma treatment should be more suitable. Finally, the operating temperature and contact pressure for roller imprinting play important roles in the conformal pattern transfer. Through the standard process, the thickness of residual layer can be reduced to 130 nm by varying the PMMA concentration. Furthermore, the residual layer is entirely removed by selectively modifying the OTS-mold surface. Whole process including PMMA coating, soft baking, atmospheric plasma treatment, and imprinting can be controlled within 20 min without air bubbles found in the PET films. Based on our demonstration, the atmospheric plasma treatment in combination with the residual-layer-free imprinting in our modified process has provided the possibility toward low cost and high throughput, roll-to-roll production. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3474984]
Keywords:contact angle;nanolithography;nanopatterning;plasma materials processing;polymer films;polymers;soft lithography;surface energy;surface treatment