Block copolymers (BCPs) are self-assembling materials able to form diverse morphologies (like lamellae, cylinders, spheres etc.) depending on the relative volume fraction of the two blocks. Thermal annealing is one of the methods used to enhance kinetics of self-assembling BCP. The orientation of the phase in thin films can be influenced by many factors e.g. substrate surface energy or film thickness.
We examine the effect of vacuum oven annealing on two lamellae-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer with molecular mass 74 kg/mol (L74) and 104 kg/mol (L104). To prepare the surface Si wafer was activated with oxygen plasma. Then to orient BCP phase vertically film of rand-PS-b-PMMA solution was spin coated and baked in 220°C for 5 minutes and the rest was rinsed with toluene. Films were prepared via flow coating onto the surface. Thermal annealing of the sample was performed by baking the wafer in 200°C for 16 hours.
Visualization with atomic force microscopy AFM was used to characterize a morphology of BCP. To generate film that can be imaged with AFM the PMMA phase in diblock copolymer was removed with exposure to UV light for 5 minutes and immersing in glacial acetic acid for another 5 minutes. Right now we are working on a relationship between the thickness of PS-b-PMMA film and the periodicity in obtained morphology.