Precision fringe metrology using a Fresnel zone plate

In scanning beam interference lithography, a resist-coated substrate is scanned under phase-locked interfering beams to pattern large gratings or grids with nanometer level distortions. To achieve design goals, it is required to measure the spatial period, phase, and rotation of the interference fringes in real-time with high precision. In this article, we report the use of a Fresnel zone plate to characterize interference fringes. With properly controlled errors, it should enable us to achieve high precision measurement of fringe characteristics for a wide range of fringe periods. The mathematical model, details of the metrological procedure, and experimental results are presented. © 2002 American Vacuum Society. @DOI: 10.1116/1.1523018#