Level sensor arrangement for lithographic apparatus and device manufacturing method

摘要

Level sensor arrangement for measuring a height of a surface of a substrate in a lithographic apparatus. The level sensor arrangement is provided with a light source emitting detection radiation towards the substrate, and a detector unit for measuring radiation reflected from the substrate in operation. The light source is arranged to emit detection radiation in a wavelength range in which a resist to be used for processing the substrate in the lithographic apparatus is sensitive.