GRATING-GRATING INTERFEROMETRIC ALIGNMENT SYSTEM

摘要

The present invention provides a grating-grating interferometric alignment system for microlithography. It includes an electromagnetic radiation source (116) of a coherent single or multiple discrete wavelengths or in some cases broadband electromagnetic radiation (132), a detector (116) of the intensity of the return electromagnetic radiation (134), x- and y- oriented independent linear mask grating (109), a checkerboard pattern wafer grating (110), and frequency component extraction (118), phase detection (120), and signal processing (121) for determining alignment from the return electromagnetic radiation (134) intensity measured as a function of the relative position of the wafer and mask grating (109, 110).