Electron Beam Lithography Tool

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Electron beam lithography is the most flexible, most versatile, high performance lithography technique for the realization of nanostructures down to the sub-10 nanometer regime. Due to a relatively small foot print of state-of-the-art instruments and moderate cost of ownership it is ideally suited for academic nanotechnology labs such as the Central Laboratory for Micro- and Nanotechnology, the central clean-room facility at RWTH Aachen University providing micro- and nanofabrication technologies for internal as well as external users. While there are two systems for electron beam lithography currently available at the Central Laboratory for Micro- and Nanotechnology, the existing tools cannot fulfil the demands of current and future research projects. In particular, the (wafer-scale) fabrication of complex mask patterns as well as the patterning of structures that straddle several write fields have been proven to be inappropriate or even impossible to achieve. The reasons for this include an inadequate pattern generator that cannot handle the large amount of data required for complex patterns and a too large stitching error. Moreover, the restricted acceleration voltage of the existing tools (a maximum of 30 kilovolts) limits the resolution and yields a substantial proximity effect. In many cases the latter cannot be corrected since the necessary, elaborate proximity correction results in such complex mask patterns that cannot be handled by the pattern generator. Finally, the limited acceleration voltage also leads to a charge-up of insulating substrates resulting in significant shifts and distortion of the intended patterns. While a reduced proximity effect and an obviation of the charge-up of insulating substrates can be achieved with rather low acceleration voltages, the lithographic resolution in this case is strongly degraded and requires very thin resist layers that are often unsuitable for etch- and lift-off processes. In addition to the scientific/technical issues of the existing two electron beam lithography tools, both are based on a scanning electron microscopy column which is not manufactured anymore. Thus, access to spare parts is only guaranteed as long as they are available and on stock of the tool manufacturer. Therefore, the Central Laboratory for Micro- and Nanotechnology will sooner or later be incapable of providing electron beam lithography, i.e. the central nanopatterning technique. As a result, funding for a new, state-of-the-art electron beam lithography tool with 100 kilovolts acceleration voltage, minimal stitching errors and capable of handling complex mask patterns is requested, that provides CMNT with the necessary nanoscale lithography capabilities to carry out research projects for the coming years.