Patent ID: 7929149
Filing Date: 2011-04-19
Classification: G01B

Abstract:
1. A machine for determining position of structures on a substrate, comprising: a measuring stage traversable in a plane defined by an axis in a X coordinate direction and an axis in a Y coordinate direction; a measuring lens arranged in an optical axis for determining position of the structures on the substrate; a measuring stage, wherein a measuring position at which at least one structure to be measured is moved by the measuring stage relative to the optical axis and wherein the substrate is positioned on the measuring stage; interferometers determining position of the measuring stage along each of the axes; and a computer connected to each interferometer for determination of position of the measuring stage, wherein the computer corrects non-linearity of each interferometer by determining position of the measuring stage along a trajectory of the measuring stage using each interferometer, wherein a part of the trajectory is directed toward a measuring position and another part of the trajectory is directed away from the measuring position; wherein the trajectory approaching the measuring position at least partially comprises motion in the X direction and in the Y direction to obtain correction values applicable to the determining position of a structure on the substrate at the measuring position, and wherein the measuring position is initially approached along the trajectory at a high velocity and then, before the measuring position is reached, at a reduced velocity to record and process data to correct the interferometer non-linearity using the computer.