Developing Micro And Nano Pattern By Using The Combination Of Photolithography And Reaction-induced Phase Separation

In the past decades, patterning has attracted much attention because of both fundamental research interests and wide industrial applications. To satisfy the growing demands for complicated micropatterns and nanopatterns as well as low cost and simple processing techniques, continuous advances in methods of fabrication of the various patterns have been developed. Among these methods, photolithography is one of the best-established technologies for micropatterning and has found wide applications in the microelectronic industry because of advantages such as large-scale production and simple processing. However, because of the wavelength limit and the diffraction of exposed light, it is difficult to obtain nanoscale structure, which is the main drawback of photolithography. Therefore, it is desired to develop a facile, effective approach to the production of nanoscale structure. Recently, reaction-induced phase separation (RIPS) has been identified in many polymer blends that can form different morphologies inside the matrix. Unlike self-assembly, which requires the use of block copolymers, RIPS technology can yield microscopic phase separation using various low-cost commercial monomers, homopolymers, or random copolymers. Unfortunately, however, it is rather difficult to obtain nanoscale structures using this technique.In this article, we first developed a facile method to fabricate micropatterns possessing nanoscale substructure based on the combined technologies of photolithography and reaction-induced phase separation. Considering that commercial materials are of special interest in industrial applications, here we chose commercial cross-linker and random copolymer as raw material.Our approach involves three parts. In the first part, TMPTA and PS-r-PMMA are spin coated onto a glass or silicon substrate to form a thin film. In the second part, photolithography was performed with the thin film to yield the micropattern. Finally, the resulting micropattern was annealed at 200℃for a certain period of time, and a PS-r-PMMA protrusion formed because of reaction-induced phase separation, which generated nanoscale substructure after the protrusion was removed by soaking in chloroform. The whole process was traced by FT-IR, XPS, AFM, which all confirmed out hypothesize. In order to establish the relationship between pattern and all factors, we investigated the effect of the kind of crosslinker and random copolymer, the ratio between the copolymer and the cross-linker, the initiator type.