Fabrication of Dual Nanopatterns by Spatial Control of Nanodomain Orientation of Block Copolymer Thin Films

Block copolymers (BCPs) with various types of nanodomains have potential application to next-generation nanolithography and storage media because of relatively low cost and time-saving process. To obtain complicated and sophisticated devices with nanolithography by using a BCP template, the control of the nanopattern of BCP at a desired area must be achieved. Here, we introduce a simple method to fabricate a dual nanopattern by spatial control of nanodomain orientation in polystyrene-block-poly­(methyl methacrylate) copolymer (PS-b-PMMA) thin films. Because most silicon substrates used in semiconductor manufacturing have a natural oxide layer (SiO_x) on the surface, the hydrophilic PMMA block is preferred over the hydrophobic PS block. This results in parallel orientation of lamellar (and cylindrical) nanodomains of PS-b-PMMA thin films. We found that when the SiO_x layer was removed by hydrofluoric acid (HF), which is termed “passivated silicon substrate”, its surface tension became the middle of PS and PMMA blocks, resulting in vertical orientation of lamellar (and cylindrical) nanodomains in thin films. When we used photoresist (PR) prepatterns on the substrate, followed by HF treatment at a selective area, dual nanopatterns consisting of parallel and vertical oriented cylinders were successfully prepared at a desired area. Finally, we fabricated a silicon substrate containing both nanoholes and nanostripes at a desired region by a simple reactive ion etching.