ASML Holding N.V.
Lithographic apparatus and device manufacturing method

Abstract:

An electromagnetic actuator is described the actuator comprising: a magnet assembly comprising: an array of permanent magnets arranged in a first direction and configured to generate, outside the magnet assembly, a spatially varying magnetic field distribution in the first direction; a ferromagnetic member onto which the array of permanent magnets is mounted; a coil assembly, at least partly arranged in the spatially varying magnetic field distribution, configured to co-operate with the magnet assembly to generate an electromagnetic force; wherein a thickness of the array of permanent magnets in a second direction perpendicular to the first direction varies along the first direction and wherein a thickness of the ferromagnetic member in the second direction varies along the first direction such that a combined thickness of the array of permanent magnets and the ferromagnetic member in the second direction is substantially constant along the first direction.