Projection lens testing with Moiré effect
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Abstract
The application of Moiré effect for testing of a lithographic projection lens is reported. The arrangement presented allows measuring magnification, distortion, field curvature and telecentricity of the lens and can be used for its fine tuning. The method is based on two matched two-dimensional gratings, positioned in mutually conjugated planes; one of them can be translated. Visual interpretation of Moiré fringe pattern allows quick diagnostics of position errors exceeding critical dimension, whereas lateral scanning is applied for measuring of smaller magnitude errors. Field curvature and telecentricity are measured by 3D scanning. Presented results are in a good agreement with those obtained elsewhere.