Nanometer scale patterning using di-block copolymer

Di-block copolymer thin films of PS-PI, PS-PB and PS-PMMA are investigated on Si substrates. The morphology evolution with polymer thickness is studied using optical microscopy. As-coated polymer exhibits a very smooth surface. After annealing polymer over glass-transition temperature, the polymer exhibits a smooth surface only at certain thickness L$_{0}$. Transmission electron microscopy is used to study the microphase separation in polymer at different stages. Clear phase separation is observed in the polymer after staining with osmium tetraoxide (OsO$_{4})$. Long time annealing increases the long-range ordering. After treatment with ozone, disappearance of dark dots due to staining of Os and appearance of white hole indicate that the polymer with double-bond is removed from copolymer film. Scanning electron microscopy shows that polymer films after reactive ion etching give a regular hole pattern which can serve as mask for nanometer scale patterning.