| 摘要 |
A lithographic apparatus includes an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and a detector for measuring the intensity of the radiation after it has passed through the projection system. The apparatus further includes a polarization changing element, such as a quarter-wave plate, that is adjustable; and a polarization analyzer, such as a linear polarizer, wherein the polarization changing element and the polarization analyzer are arranged in order in the radiation beam path at the level at which a patterning device would be held by the support. By taking intensity measurements, using the detector, for different rotational orientations of the polarization changing element, information on the state of polarization of the radiation at the level of the patterning device can be obtained. Because the polarization analyzer is located before the projection system, the measurements are not affected by the fact that the detector is located after the projection system, such as at the level of the substrate. |
