Patterning block copolymer thin films by deep X-ray lithography

Abstract

Developing fast, cheap and reliable micro and nanofabrication technologies for block copolymer thin films is a key issue for exploiting the wide potential applications of this class of materials. We have used a synchrotron source of high energy photons (hard X-rays) for developing a lithographic tool that allows direct writing of block-copolymer thin films. We have exposed films prepared by a tri-block copolymer, Pluronic F127, to increasing doses of radiation to evaluate the effect of high energy X-rays on the samples. The as-deposited films show a crystalline structure due to the crystallization of polyethylene oxide chains in Pluronic F127; the exposure to low doses causes a phase change from crystalline to amorphous, as is shown by infrared spectroscopy. Another effect of the exposure to X-rays of the block copolymer films is the surface roughness reduction which has been observed by atomic force microscopy, At higher doses the X-rays erase the film from the substrate allowing the formation of patterned polymeric structures. Deep X-ray lithography has proved to be a very effective tool to pattern block copolymer films by a direct, top-down method.