Lithographic apparatus, device manufacturing method

摘要

To compensate for birefringence of a mask in a lithographic projection apparatus, the birefringence of a mask is measured and stored as birefringence data in a data storage device. A birefringent compensation element is disposed in the optical path of the lithographic projection apparatus. Appropriate adjustments of the compensation element are determined as those optimally reducing impact of the mask birefringence on the state of polarization at substrate level.