Stabilized two-dimensional linewidth enhancement in direct laser lithography

In order to realize a small linewidth two-dimensional direct laser lithographic technique with enhanced resolution, we propose two apparatuses. The first one uses a polarizing beam splitter to separate a source beam into two output beams, and these two beams overlap on the focal point and make a narrow interferogram that sharpens the focused beam spot. The direction of the sharpened beam spot is controlled by a tilting mirror. This scheme is fast and easy to align. However, one serious problem, the interferogram shifting phenomenon, was observed during a long term fabrication. To obtain long term stability, we propose the second scheme that employs a calcite wave plate module attached to a motorized rotary motor. In this setup, the direction of the focused beam spot is controlled by the rotary motor.