Beam pen lithography based on focused laser diode beam with single microlens fabricated by excimer laser

A method is proposed to minimize the focused spot size of an elliptically-diverging laser diode beam by means of a circular aperture and a single plano-convex aspherical microlens. The proposed microlens is fabricated using an excimer laser dragging method and has two different profiles in the x- and y-axis directions. The focused spot size of the beam is examined both numerically and experimentally. The feasibility of the proposed approach for beam pen lithography applications is demonstrated by patterning dotted, straight-line and spiral features on a photo resist layer followed by thin gold layer deposition and metal lift-off. The minimum feature size for dotted pattern is around 2.57 μm, while the minimum line-widths for straight-line and spiral pattern are 3.05 μm and 4.35 μm, respectively. Thus, the technique can be applied to write any arbitrary pattern for high-resolution lithography.