Patent ID: 6819425
Filing Date: 2004-11-16
Classification: G03F

Abstract:
A lithographic projection apparatus comprising:a radiation system that provides a beam of radiation; a support structure that supports patterning structure, the patterning structure serving to pattern the beam according to a desired pattern; a substrate table that holds a substrate; a projection system that projects the patterned beam onto a target portion of the substrate; and a displacement measuring system that measures the position of a moveable abject, comprising one of said support structure and said substrate table, in at least two degrees of freedom, said displacement measuring system comprising at least one grid grating mounted on said moveable object and at least one sensor head that measures displacements of said grid grating in at least two degrees of freedom, wherein the or each said grid grating is positioned so as to be substantially coplanar with a functional surface of said patterning structure supported by said support structure or a substrate held by said substrate table.