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US 7,453,641 B2Granted
Structures and methods for reducing aberration in optical systems
AssigneeASML Netherlands B.V.
InventorJames P. McGuire, Jr.
Life of this patent
Estimating the term…
Abstract
An optical system includes at least one cubic crystalline optical element aligned along an optical axis, the at least one cubic crystalline optical element being birefringent and imparting retardance on a beam of light propagating through the optical system along the optical axis, and polarization rotation optics inserted along the optical axis and selected to rotate the polarization of the beam of light to at least partially reduce the retardance.
Claims64
An optical system comprising:
- at least one cubic crystalline optical element aligned along an optical axis, said at least one cubic crystalline optical element being birefringent and imparting retardance on a beam of radiation propagating through said optical system along said optical axis;
- and
- a polarization rotation optic inserted along said optical axis to rotate the polarization of said beam of radiation, said polarization rotation optic comprising one or more rotators configured to rotate an input polarization by ±90(2n+1) degrees, where n is an integer, and output the rotated polarization to an optical element imparting retardance to at least partially reduce said retardance imparted by the at least one cubic crystalline optical element.
An optical apparatus, comprising:
- a support configured to hold a patterning device arranged to pattern a beam of radiation;
- and
- a projection system configured to project the patterned radiation beam onto a radiation sensitive layer of material disposed on a substrate, said projection system including:
- a plurality of optical elements having birefnngence that introduces retardance to said radiation beam;
- and
- a circular retarder having orthogonal circular eigenpolarization states, said circular retarder configured to produce phase delay between said eigenpolarization states substantially equivalent to an odd number of quarter wavelengths of said radiation beam, such that retardance introduced through at least one of said plurality of optical elements is substantially offset by retardance introduced into said radiation beam upon transmitting said radiation beam through at least one of said plurality of optical elements after passing said radiation beam through said circular retarder.
3 more elements
An optical system comprising:
- a cubic crystalline optical element being birefringent and arranged to impart retardance on a beam of radiation propagating through said optical element;
- and
- a polarization rotation optic inserted along said optical axis to rotate the polarization of said beam and output the rotated polarization to an optical element configured to impart, due to the rotation of the polarization, retardance to said beam that at least partially reduces said retardance imparted by the at least one cubic crystalline optical element.
Dependencies are inferred from the claim text.