Evaluation of three exposure schemes for absorbance-modulated interference lithography

Using absorbance-modulated interference lithography (AMIL), subdiffraction-limited gratings can be patterned using a variety of configurations. Three main configurations are compared here using results from a finite-element modeling simulation study, with combinations of standing-wave interference illumination and/or flood illumination for the two wavelengths needed for AMIL. Flood illumination for the short-wavelength exposure combined with standing-wave exposure in the longer wavelength is the simplest configuration, but does not provide the best imaging performance. This is achieved for standing-wave illumination for both sources with matched periods in the standing waves. For 405 nm short-wavelength exposure and azobenzenelike material characteristics in the absorbance-modulation layer 133-nm period grating images are shown with image contrast of 0.58. The sensitivity to misalignment of the two standing wave periods has been studied, and no significant increase in linewidth is found for phase errors between the two interference patterns of up to 20% of the period. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3640757]