Off-Axis Catadioptric Projection Optical System for Lithography

An optical system, comprising:

• an off-axis mirror segment configured to receive modulated light, an axis of the off-axis mirror segment differing from an axis of a substrate, the off-axis mirror segment is a first mirror segment within the optical system;
• a fold mirror configured to receive the modulated light from the off-axis mirror segment;
• a relay configured to receive the modulated light from the fold mirror and to focus the modulated light;
• an aperture stop configured to receive the modulated light from the relay;
• and
• a refractive lens group configured to focus the modulated light onto the substrate.

An optical system, comprising:

• an off-axis mirror segment configured to receive modulated light, an axis of the off-axis mirror segment differing from an axis of the substrate, the off-axis mirror segment being a first mirror within the optical system;
• a concave mirror configured to receives modulated light from the off-axis mirror segment;
• a negative refractive lens group positioned between the off-axis mirror segment and the concave mirror;
• a relay configured to receives light from the concave mirror configured to has passed through the refractive lens group and configured to focuses the modulated light;
• an aperture stop configured to receives the modulated light from the relay;
• and
• a refractive lens group configured to focuses the modulated light onto the substrate.

A lithographic apparatus, comprising:

• an illumination system configured to supply a beam of radiation;
• a pattern generator configured to pattern the beam;
• and
• a projection system configured to project the patterned beam along a predetermined beam path onto a substrate, wherein the projection system comprises an off-axis mirror segment configured to receive the patterned beam from the pattern generator, wherein an axis of the off-axis mirror segment differs from an axis of the substrate, wherein the off-axis mirror segment is the first mirror segment within the projection system, wherein the projection system includes at most three mirrors.

A method comprising:

• transmitting a patterned beam parallel to an axis of an off-axis mirror segment differing from an axis of a substrate that receives an image from a projection system with the off axis mirror segment, the off-axis mirror segment being a first mirror segment within the projection system;
• reflecting the patterned beam with the off-axis mirror segment;
• focusing the reflected patterned beam;
• and
• imaging the reflected patterned beam onto the substrate.