Deep subwavelength patterning via absorbance modulation

Creating very small structures in the resist exceeding di raction limit is becoming a bottle-neck in lithography especially for nanoscale features. A novel optical lithography technique that has the ability to overcome the di raction barrier is Absorbance Modulation Interferometric-Lithography (AMIL). Feasibility of this technique is experimentally veri ed. In this approach of absorbance modulation, a standing wave at wavelength ?2 (633nm) is overlaid with a uniform beam from a light-emitting diode with a center wavelength at ?1 (310nm). Both beams illuminate a photoresist lm overcoated with a photochromic layer. This photochromic layer localizes the transmitted light at ?1 to subwavelength spatial dimensions. The subwavelength lines are spaced by a di raction-limited grating period. In order to generate dense lines, the sample is mounted on a single-axis high precision scanning stage that will enable multiple exposures.