Research on a New Lithography Method Utilizing Laser Speckles for Printing Random Patterns

A new simple and low-cost optical lithography method utilizing speckles was developed for printing random patterns on surfaces of three-dimensinal objects with various shapes, and patterning characteristics were investigated by assembling a handmade exposure system. In the system, a laser beam was irradiated on a transparent diffuser plate, and generated speckles were projected onto a wafer coated with a resist. As a result, resist patterns with random shapes were successfully formed after the development. The size and number of patterns were controllable by adjusting the exposure time. Pattern sizes were between several tens microns and a few hundred microns. It was demonstrated also that the pattern sizes were controlled by changing the wafer position from the diffuser plate. However, the sizes and numbers of patterns were varied together when the exposure time or the distance between the diffuser and the wafer was changed.