Method for detecting scale of diffractive optical structure for interferometric study of lithographic optics, involves detecting direction of radiation reflected on radiation elements, and wavelength of radiation on optical arrangement

摘要

The method involves irradiating an optical arrangement with the radiation (170). A retroreflector (160) is arranged at the downstream of diffractive optical structure (150). The diffractive optical structure has several diffraction regions (151-155) reflected in different ways to the optical arrangement radiation elements (171-175). The direction of radiation reflected on optical arrangement radiation elements, and radiation wavelength are detected. The scale of diffractive optical structure is determined based on the detected radiation directions and wavelength of radiation. Independent claims are included for the following: (1) apparatus for detecting scale of diffractive optical structure; (2) method for determining change in length of element having diffractive optical structure; and (3) method for determining temperature of element having diffractive optical structure.