Methods for reducing polarization aberration in optical systems
AssigneeASML Netherlands B.V.
InventorJames P. McGuire, Jr.
Life of this patent
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Abstract
An optical system includes multiple cubic crystalline optical elements and one or more uniaxial birefringent elements in which the crystal lattices of the cubic crystalline optical elements are oriented with respect to each other to reduce the effects of intrinsic birefringence and produce a system with reduced retardance. The net retardance of the system is reduced by the cancellation of retardance contributions from the multiple cubic crystalline optical elements and the uniaxial birefringent element. The optical system may be used in a photolithography tool to pattern substrates such as semiconductor substrates and thereby produce semiconductor devices.
Claims24
A method of optically imaging, comprising:
- propagating light through a plurality of cubic crystal elements including local birefringence axes and possessing intrinsic birefringence that produce first retardance aberrations, said plurality of cubic crystal elements being selected such that more than about 70% of the local birefringence axes are substantially directed around circular paths about an optical axis of said plurality of cubic crystal elements;
- and
- propagating said light through at least one optical element comprising a uniaxial birefringent medium thereby introducing second retardance aberrations substantially identical in magnitude and substantially conjugate in shape to said first retardance aberrations so as to substantially offset said first retardance aberrations.
Dependencies are inferred from the claim text.