LAUSR

To improve the quality of grating masks made by scanning beam interference lithography, this article established a mathematical model of step-scanning exposure and analyzed the effects of the beam drift error on the interference image. Beam angle drift can be decomposed into the drift error δx in the exposure plane (XOZ plane) and the drift error δy perpendicular to the plane. Analysis shows that the δx has a major impact on the interference fringes during exposure, which may affect the precision of phase lock. δy leads to the appearance of deflected interference strips and affects the exposure dose. When a low-frequency drift error appears in the light path, the exposure contrast on the photoresist will decrease with the exposure process, which makes the fabrication of large-size diffraction gratings difficult. Furthermore, taking advantage of the characteristics of a scanning beam interference lithography system, an exposed beam stable system was designed that can effectively suppress the low-frequency drift of the beam. The total beam angle control accuracy is better than the 2.7 μrad, and position control accuracy is better than 3.9 μm (both for 1σ), which achieves the expected goal of the design.