Miniaturization of Scattered Random Patterns Formed by Lens·less Speckle Lithography

A new method without using a projection lens for easily and inexpensively forming random micro-patterns on large area surfaces and three-dimensional shapes such as steps and curved surfaces was developed in the past research. In the method named “Speckle lithography”, speckle light was used for forming scattered random patterns on surfaces coated with a resist film. In this paper, further miniaturization of patterns was investigated. In a renovated handmade exposure system, the beam diameter of laser beam irradiated to the diffusion plate was expanded from 4 mm to 17 mm using a beam expander. And, the distance between the diffusion plate and the wafer was shortened from 45 mm to 1 mm. As a result, random dot resist patterns with a minimum size of 1 μm or less were successfully formed on entire exposed areas limited to 10×10 mm.