Patent ID: 7986409
Filing Date: 2011-07-26
Classification: G01B,G03F,G06T

Abstract:
1. A method for determining a centrality of masks, comprising the steps of: positioning a mask in a coordinate measuring device on a measurement table displaceable in a direction perpendicular to an optical axis of an imaging measurement system, wherein a position of the measurement table is measured interferometrically, the coordinate measuring device defining a measuring device coordinate system; determining a position of at least a first and a second outer edge of the mask in the measuring device coordinate system; determining an angle at which the first and second outer edge meet from the position of the first and second outer edge in the measuring device coordinate system; determining a position of a mask coordinate system with respect to the measuring device coordinate system based on at least two structures on the mask; determining a relative distance from one of the at least first and second outer edges to the at least two structures, and determining by the coordinate measuring device the coordinates of the at least two structures with respect to the first and second edge and determining whether the first and second edges are within a tolerance range.