Holographic Lithography with Endpoint Detection of Resist Development

Abstract

Grating patterns with a period of about 0.4 µm are fabricated by means of holographic lithography with a He-Cd laser (λ=441.6 nm). In the fabrication process to develop a resist film sample a He-Ne laser beam irradiates the sample and its reflection intensity is observed. The reflection intensity of the He-Ne laser does not change periodically during the development. We calculate the He-Ne laser reflection intensity from the resist grating during the development assuming either the rectangular or the triangular resist grating profiles. The calculated reflection intensity with the triangular profile shows good agreement with the experimental one. The reflection intensity can be applied to the endpoint detection of the development. We have fabricated resist gratings with vertical profiles whose lines and spaces are approximately 0.1 µm and 0.3 µm in width, respectively. Very fine lines of 0.06 µm in width with vertical walls have also been fabricated by controlling the development time. Au gratings with 10 nm thickness can be made directly using the lift-off technique.