Method of manufacturing a projection objective and projection objective manufactured by that method

摘要

A method of manufacturing a projection objective including the steps of defining an initial design for a projection objective and optimizing the design using a merit function having a plurality of merit function components (AB,IRRAD EFF ), each of which reflects a particular quality parameter. One of that merit function components defines a maximum irradiance requirement requiring that a normalized effective irradiance value representing an effective irradiance (IRRAD EFF ) normalized to an effective irradiance in an image surface of the projection objective does not exceed a predefined irradiance threshold value (IRRTV) on each optical surface of the projection objective except for a last optical surface directly adjacent to an image surface of the projective objective. Optical surfaces positioned within caustic regions and/or critically small effective sub-apertures on optical surfaces are thereby systematically avoided.