Investigation of dose and development time for thin e-beam resist poly(methyl methacrylate) for large area dense nanopattern applications

With the advance of nanotechnology, the demand for very dense nanopatterns over large areas continuously increases. Electron beam lithography is one of the main tools to realise this type of nanopattern. In this study we investigate the effect and interrelation of dose and development time for electron beam resist poly(methyl methacrylate) (PMMA) for the realisation of very large area and very dense nanopatterns. For this purpose a pattern consisting of a lattice of holes with radius of 80 nm and lattice constant of 200 nm has been designed, electron beam lithography is realised on a thin resist and a detailed SEM image inspection of the pattern is recorded. Hough transform, a pattern recognition method for the digital images, is applied to SEM images to measure the radii of the holes on the images. Interrelation between dose and development time is investigated. It is found that for a very large area of dense nanopatterns the lithographic process works better for development times shorter than typically used ones.