This paper presents an analysis of depth of focus (DOF) based on optics or detector pixel size in optical microscopes with electronic cameras. We first generally analyze DOF based on optics in different cases related to the spatial coherence of illumination and the object, and then use a design example of an infinity correction system for a review system to show DOF dependence on illumination numerical aperture. Finally, we discuss DOF increase based on detector pixel size, and then use a design example of an infinity correction system for the inspection system. Both designs are verified with simulation using CODEV, an optical design software. Both designs are used in KLA STAR-light^TM multi-surface inspection (backside glass and pellicles).

Date Published: 21 May 1996
PDF: 7 pages
Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); doi: 10.1117/12.240128

Published in SPIE Proceedings Vol. 2725:
Metrology, Inspection, and Process Control for Microlithography X
Susan K. Jones, Editor(s)