Patent ID: 8884253

Claim:
A system for magnetically shielding a charged particle lithography apparatus, the system comprising: a first chamber having walls comprising a magnetic shielding material, the first chamber enclosing, at least partially, the charged particle lithography apparatus; a second chamber forming part of a vacuum chamber and having walls comprising a magnetic shielding material, the second chamber enclosing the first chamber; a moveable stage element arranged for supporting a substrate support structure, and positioned outside the first chamber and inside the second chamber; a set of two coils disposed in the second chamber outside of the first chamber and on opposing sides of the first chamber and the moveable stage element, the two coils having a common axis, and at least one magnetic field sensor positioned outside the first chamber and inside the second chamber, for measuring the magnetic field within the second chamber, wherein the first chamber is provided with an opening at a side facing the moveable stage element, for allowing charged particle radiation originating from the lithography apparatus to be exposed on a substrate provided on the substrate support structure, and wherein the at least one magnetic field sensor is positioned between the opening and the moveable stage element, wherein the system comprises a control system configured for controlling the currents through the coils based on information provided by the at least one magnetic field sensor, so as to nullify the magnetic field measured between the opening and the moveable stage element during operation, wherein the distance between a coil and the closest wall of the second chamber measured along a direction substantially parallel to the common axis is smaller than such distance between said coil and the closest wall of the first chamber.