Lithographic performance of ZEP520A and mr-PosEBR resists exposed by electron beam and extreme ultraviolet lithography

摘要

Pattern transfer by deep anisotropic etch is a well-established technique forfabrication of nanoscale devices and structures. For this technique to beeffective, the resist material plays a key role and must have high resolution,reasonable sensitivity and high etch selectivity against the conventionalsilicon substrate or underlayer film. In this work, the lithographicperformance of two high etch resistance materials was evaluated: ZEP520A(Nippon Zeon Co.) and mr-PosEBR (micro resist technology GmbH). Both materialsare positive tone, polymer-based and non-chemically amplified resists. Twoexposure techniques were used: electron beam lithography (EBL) and extremeultraviolet (EUV) lithography. These resists were originally designed for EBLpatterning, where high quality patterning at sub-100 nm resolution waspreviously demonstrated. In the scope of this work, we also aim to validatetheir extendibility to EUV for high resolution and large area patterning. Tothis purpose, the same EBL process conditions were employed at EUV. The figuresof merit, i.e. dose to clear, dose to size, and resolution, were extracted andthese results are discussed systematically. It was found that both materialsare very fast at EUV (dose to clear lower than 12 mJ/cm2) and are capable ofresolving dense lines/space arrays with a resolution of 25 nm half-pitch. Thequality of patterns was also very good and the sidewall roughness was below 6nm. Interestingly, the general-purpose process used for EBL can be extendedstraightforwardly to EUV lithography with comparable high quality and yield.Our findings open new possibilities for lithographers who wish to devise novelfabrication schemes exploiting EUV for fabrication of nanostructures by deepetch pattern transfer.