| 摘要 |
In a lithographic projection apparatus, adjustment of the projection system, e.g. to compensate for lens heating effects, is performed by determining a region of interest for a given pattern and illumination arrangement, the region of interest being a non-circular region of a pupil plane of the projection system through which substantially all of the radiation of the modulated beam that contributes to formation of the image passes; obtaining a set of basis functions that are orthogonal over the region of interest; expressing the wavefront in the pupil plane in terms of the basis functions that are orthogonal over the region of interest and a set of coefficients; and determining a value of a control setting to minimize the values of the coefficients. |
