Current chemicals used in electron beam (e-beam) lithography generate safety and waste management issues. To replace them, chitosan, a natural and abundant polymer soluble in water based solutions, was assessed as a positive and water developable resist for a two-layer e-beam lithography and as a mask for transfer by etching in silica. Fifty nanometer line patterns were successfully obtained in a chitosan film by e-beam lithography at doses between 160 and 300 μC cm−2, then, transferred into a silica layer by CHF3 plasma reactive ion etching with respect of the feature dimensions.

We report the use of the Second Harmonic Generation response from a riboflavin doped chitosan film as a characterization method of the film morphology. This film is of particular interest in the development of new and bio-sourced material for eco-friendly UV lithography. The method allows us to determine how riboflavin is distributed as a function of film depth in the sample. This possibility is of importance in order to have a better understanding of the riboflavin influence in chitosan films during the lithography process. On the contrary, linear optical techniques provide no information beyond the mere confirmation of the riboflavin presence.