Epoxidized novolac resist (EPR) for high-resolution negative- and positive-tone electron beam lithography

An epoxidized novolac resist (EPR) has been evaluated for high resolution negative and positive tone electron beam lithography. EPR is a chemically amplified experimental resist developed in 'Demokritos' for e-beam lithography. It is characterized by high resolution, high sensitivity and very good post-exposure bake (PEB) latitude. Wet development after the post exposure bake (PEB) step gives a negative tone process while silylation and dry development gives a positive tone process. In this work, EPR's high resolution capabilities (below 0.25 micrometer) are demonstrated for both processes. Critical process parameters such as the photo acid generator (PAG) content of the resist, the PEB temperature and the effect of the delay time between exposure and PEB are examined. Delay effects are studied both for directly e-beam written resist profiles as well as for silylated profiles. The experimental work is accompanied by detailed modeling of lithographic processes, including acid diffusion, gel formation, silylation and delay effects.