Patent ID: 8248618
Filing Date: 2012-08-21
Classification: G01B

Abstract:
1. Method for determining a position of structures on a mask comprising the following steps: a. providing a metrology tool with a measurement table which is movable in an X-coordinate direction and in an Y-coordinate direction, and a computation unit assigned to a detector element of a camera; b. defining a measurement window on the detector element of the metrology tool, wherein the detector element comprises a plurality of pixels arranged in rows and columns; c. positioning of the measurement table in the X-coordinate direction and in the Y-coordinate direction in such a way that a measurement objective of the metrology tool images at least a part of a respective structure to be measured into the measurement window of the detector element; d. recording a first intensity profile along a first measurement direction, which is parallel to the X-coordinate direction and recording a second intensity profile along a second measurement direction, which is parallel to the Y-coordinate direction; and e. combining the first and the second intensity profiles representing a function of two variables of the image of the structure recorded from the measurement window defined in the detector element; f. integrating a centre of gravity algorithm into an existing software structure of the metrology tool for determining a two-dimensional position of a centre of gravity with respect to a coordinate system of the metrology tool from the first intensity profile and the second intensity profile and for determining, based on the position of the centre of gravity, the positions of edges of the structure which are essentially orthogonal to the first measurement direction and the positions of edges of the structure on the mask which are essentially orthogonal to the second measurement direction.