| 摘要 |
Methods are disclosed for determining and accounting for errors in a moving mirror of an interferometer used for determining the position of a stage or the like in a microlithography system or other system requiring highly accurate positioning. In an embodiment, straight lines that approximate respective curves of mirror surfaces (29a), (29b) are determined with respect to a coordinate system defined on a wafer table. The straight lines are determined by a least-squares method. Also determined are angles (Ψu) and (Ψv) formed by straight lines (Lu) and (Lv) relative to coordinate axes (u) and (v), respectively. Intersections with the coordinate axes u, v are (Bu, 0) and (0, Bv), respectively. The distances to points U1 and V1 on mirror surfaces 29a and 29b with respect to straight lines Lu and Lv are omegau(v) and omegav(u), respectively, and the angles with the tangent lines of the points U1 and V1 are betau(v) and betav(u), respectively. Equations of the mirror surfaces thus are: u=v[Ψu+omegau(v)]+Bu+betau(v), and v=u[Ψv+omegav(u)]+Bv+betav(u).
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