Catadioptric Optical System for Scatterometry

An optical system for scatterometry, comprising:

• an optical element that deflects electromagnetic radiation;
• and
• an objective system comprising a monolithic glass element optically contacted with the optical element and configured to receive the deflected electromagnetic radiation, the monolithic glass element comprising
• a first surface that reflects the electromagnetic radiation,
• a second surface that receives the electromagnetic radiation from the first surface and reflects and focuses the electromagnetic radiation toward a target portion of a substrate, and
• a third surface, wherein the electromagnetic radiation reflected and focused by the second surface exits the monolithic glass element substantially perpendicular to the third surface,
• wherein the optical element and monolithic glass element are comprised of the same type of material.

A catadioptric optical system for scatterometry, comprising:

• a refractive lens group that conditions electromagnetic radiation to correct one or more aberrations of the catadioptric optical system;
• a first monolithic glass element that receives the electromagnetic radiation from the refractive lens group and is adapted to focus the electromagnetic radiation into a first focused spot;
• and
• a second monolithic glass element that receives the electromagnetic radiation from the first monolithic glass element and is configured to focus the electromagnetic radiation into a second focused spot on a target portion of a substrate,
• wherein the electromagnetic radiation enters the second monolithic glass element substantially perpendicular to a first spherical refractive surface and exits the second monolithic glass element substantially perpendicular to a second spherical refractive surface.