Three Dimensional Maskless Ultraviolet Exposure System Based on Digital Light Processing

This paper reports the development of a three dimension maskless photolithography system with an oblique scanning method based on digital light processing technology. The system consists of a UV light source, a digital micromirror device (DMD), a microlens/pinhole array, two optical projection lenses, and a three-axis (xyz) servo-controlled stage. The optical system can form a rectangular array of UV spots with a diameter of few μm directly on the surface of a sample sitting on the stage. A photoresist (PR) layer is coated on the sample surface. Using an oblique scanning approach, the whole area of PR layer can be exposed by this UV exposure system in a maskless manner. Since the energy intensity of each UV spot can be independently modulated by a corresponding group of micromirrors in the DMD, and a three-dimensional (3D) UV dosage distribution can be achieved through computer programming on the DMD and the xyz stage. After developing processes, 3D PR microstructures with arbitrary patterns and/or surface profiles can be readily formed by this maskless lithography system. Experimental results will be addressed as well as potential applications for 2D and 3D microfabrication.