Two-photon nanolithography of positive photoresist thin film with ultrafast laser direct writing

The authors investigate two-photon nanolithography of a positive photoresist thin film and the influence factor of spatial resolution. A spatial resolution of 85 nm, about one-ninth of the laser wavelength at 780 nm, has been realized by using commercial positive AZ P4620 photoresist. Theoretical analysis based on the exposure kinetics of photoactive compound of diazonaphthoquinone is consistent with experimental results. The trench's cross-section shape and spatial resolution are influenced by the standing wave interference caused by the incident and reflected light. This study would provide a protocol for fabricating micro/nanodevices by femtosecond laser direct writing of positive photoresists. (C) 2013 AIP Publishing LLC.