System and Method Configured to Provide Predetermined Depth Of Focus and to Control Irradiance Distribution
AssigneeNikon Corporation
InventorsDavid M. Williamson, Daniel G. Smith
Life of this patent
Estimating the term…
Abstract
A system and method for illuminating an imaging optical system are provided, designed to spread the irradiance distribution at a pupil located at a mirror, to decrease the maximum irradiance on the mirror in the pupil, while maintaining a predetermined depth of focus of the imaging optical system (i.e. a depth of focus that is predetermined to be acceptable for the particular imaging optical application).
Claims4
An illumination system that provides illumination to an imaging optical system configured to project radiation along an imaging optical path from a reticle to an image plane, to maintain a predetermined depth of focus of the imaging optical system while controlling the maximum irradiance directed at a mirror located at a pupil in the imaging optical path, the illumination system configured to illuminate the reticle at a plurality of angles and to spread the irradiance distribution in one or more predetermined directions at the pupil.
A method for illuminating an imaging optical system that projects radiation along an imaging optical path from a reticle to an image plane, to maintain a predetermined depth of focus of the imaging optical system while controlling the maximum irradiance directed at a mirror located at a pupil in the imaging optical path, comprising projecting radiation in a manner that illuminates the reticle at a plurality of angles and spreads the irradiance distribution in one or more predetermined directions at the pupil.
Dependencies are inferred from the claim text.