Patent ID: 6208407
Filing Date: 2001-03-27
Classification: G03F

Abstract:
A method of projecting a mask pattern on a plurality of substrate fields of a substrate provided with a radiation-sensitive layer, by a projection beam and a projection system, wherein prior to introducing a substrate holder with the substrate into the projection beam and underneath the projection system, a surface profile of the substrate is determined for each substrate field, the method comprising:measuring a height of the substrate field in a direction parallel to an axis of the projection beam while moving at least one of a first height sensor and said substrate field with respect to the other in a direction perpendicular to the axis of the projection beam;measuring a height of a reference plane of the substrate holder with a second height sensor separate from the first height sensor;establishing a relation between the height of the substrate field and the height of the reference plane of the substrate holder and determnining an ideal height of the reference plane of the substrate holder based on an ideal height of the substrate field;storing the ideal height of the reference plane of the substrate holder for the substrate field in memory; andafter the substrate has been introduced into the projection beam, determining the height of the reference plane of the substrate holder for each substrate field by using a third height sensor separate from the first and second height sensors, and adjusting the height of the substrate holder based upon such determination and the stored ideal height of the reference plane of the substrate holder for each substrate field.