Enhancement of proton beam writing in PMMA through optimization of the development procedure

The development step of the proton beam writing (PBW) process plays an important role in the performance characteristics that can be achieved with a resist-developer system. A common developer for PBW in PMMA resist is the mixture IPA/water, used in combination with conventional dip development.In this paper, we investigate the use of the GG-developer, much used in the LIGA-process, and show that the GG-developer is able to dip develop proton beam written structures of feature sizes down to 133 nm in a PMMA layer of 2.4 μm thickness. Moreover, both contrast and sensitivity are found to be higher for the GG-developer compared to dip development in 7:3 IPA/water.The development method as well as the type of developer influences resist development. The effect of megasonic agitation (frequency of 1 MHz) on the development of structures in PMMA was investigated for the developer 7:3 IPA/water. Compared to conventional dip development, structures developed with megasonic agitation showed larger feature sizes, indicating that the development rate was increased. However, performance characteristics were not enhanced: both contrast and sensitivity were found to be lower than after dip development in 7:3 IPA/water.