Measurement and Calibration for Point Array Oblique Scanning Ultraviolet Exposure

Abstract

In this study an optical measurement and calibration process is established to resolve the errors and defects caused by optical distortion of image projection lenses in an ultraviolet (UV) maskless lithography system This UV maskless lithography system is based on digital-micromirror-device (DMD) and oblique scanning of an UV point array Using a high-resolution image sensor and a high precision x-y-z motorized stage the coordinates of UV spots are accurately measured The measured point array is then characterized with an optical distortion model and used for correcting the algorithm in preparing DMD images for UV exposure The UV light in this maskless lithography system has a wavelength of 405 nm The UV light is modulated and reflected by the DMD and then projected by the first imaging lens The projected UV light is collected by arrayed microlens and focused into arrayed pinholes which acts as a spatial filter array Finally the UV illuminated pinhole array is projected by the second image lens onto a photoresist layer for UV patterning based on obliquely scanning of the projected UV spots The experimental results show that the distortion of the optical imaging lens used in this study is about 0 3 % in the projection range of 14 08 x10 56 mm^2 and the max periodic defect is about 30 μm The point array detection and calibration process proposed by this study can reduce the periodic defect down to 2 μm and successfully realize arbitrary UV patterning with a minimum linewidth/spacing of 10 μm

Date of Award	2020
Original language	English
Supervisor	Yung-Chun Lee (Supervisor)