Optimization of pattern quality in DMD scanning maskless lithography: A parametric study of the OS3L exposure algorithm

Abstract

In digital micromirror device (DMD) scanning maskless lithography systems, the pattern accuracy has a critical effect on the final component quality. However, the patterning performance is highly sensitive to the parameters used in the scanning process. Accordingly, this study examines the effects of three key parameters (the rotation angle of the DMD array, the step size, and the optical distortion of the image projection lens) on the patterning quality of a DMD-based scanning maskless lithography system utilizing an oblique scanning and step-strobe lighting (OS³L) exposure algorithm. The MATLAB simulation results show that the optical distortion of the image projection lens causes an uneven distribution of the exposure points along the x-axis direction, with sparser focal spots on the sides of the exposure field and denser spots in the center. In addition, the results suggest that the DMD rotation angle should be close to (but not less than) the critical angle, i.e., the angle at which the maximum horizontal resolution is obtained. Finally, the light spot distribution is extremely sensitive to the step size, but the relationship between them is unpredictable and nonlinear. Consequently, the effects of the step size on the light spot distribution should be checked on a case-by-case basis. Overall, the results presented in this study provide useful guidelines for the selection of the parameter settings that optimize the patterning quality in DMD-based scanning maskless lithography systems using the OS³L exposure algorithm.