A method for measuring stage grid accuracy of stepper

The XY stage of a stepper is used for measuring distortion aberrations, in which case, it is necessary to bring the stage grid as close to optimality as possible. Since there was no method available for measuring the stage grid deformation directly, there was a method devised for measuring the stage grid from the value of the contiguity superposition mark. This paper proposes a method which is based on "two-dimensional least square serial two-point method". In this paper measurement principles are presented and measurement accuracy is investigated by using simulation to examine mark measurement errors. Simulation results show an improvement in stage grid measurements when the proposed measurement method is used.