This paper proposes a method for improving the patterning resolution of conventional contact photolithography from the micrometer, down to the sub-micrometer scale. The key element is a soft polydimethylsiloxane (PDMS) photomask, which is first replicated from a silicon mold and then patterned with a black photoresist (PR) layer to selectively block ultraviolet (UV) light. This soft PDMS photomask can easily form an intimate and conformable contact with a PR-coated substrate and hence can perform contact photolithography with high pattern resolution. The fabrication processes of this black-PR/PDMS soft photomask are experimentally carried out. Using the fabricated soft photomask, UV patterning by contact photolithography with the smallest line-width of 170 nm over a 4” wafer area was successfully achieved. The advantages and potentials of this new type of contact photolithography will be addressed.

This paper presents an improved excimer laser micromachining method for fabricating arrayed microstructures with a predesigned surface profile. The proposed method is developed from a conventional biaxial laser dragging method, but numerical analysis and optimal pattern design on the contour mask are introduced so that the machined surface profiles can be well controlled and matched to the designed profiles. To demonstrate the capability of this new approach, an array of aspheric microlenses that have analog surfaces for minimizing the focal spot sizes of the lenses is designed and fabricated. An array of 10×10 microlenses with an aperture size of 100 μm and a designed aspheric profile are obtained experimentally. The machined surface profiles are closely matched to their designed ones, with a profile deviation of less than 1 μm. Furthermore, the machined surfaces are smooth, with an average surface roughness of around 2 nm. Optical measurements on these machined aspheric microlenses show minimized focal spot sizes approaching their optical diffraction limits.