| 摘要 |
Astigmatism-correction devices are disclosed for use in a charged-particle-beam (CPB) microlithography apparatus and methods and that do not produce higher-order aberrations when correcting deflection aberrations. The CPB microlithography apparatus includes a projection-optical system that includes first and second projection lenses and associated deflectors. The astigmatism-correction device can include a first coil array associated with the first projection lens upstream of an aperture, and a second astigmatism-correction device associated with the second projection lens downstream of the aperture. In each coil array, the nominal half-angle of the constituent coils is 30°. With such a configuration, higher-order aberrations that otherwise would be produced by the deflectors are reduced nearly to zero, making it possible to use large electrical currents in the deflectors. Specifically, deflection-astigmatism aberrations and hybrid deflection-astigmatic distortions otherwise produced by the deflectors are eliminated.
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