Patent ID: 7602492

Claim:
An overlay measuring method comprising: setting a map corresponding to a wafer using a measuring apparatus computer and a reference recipe output from a host computer; inputting setup data comprising a setup position and an allowable range corresponding to the setup position to the measuring apparatus computer, wherein the setup position is obtained from reticle information; recognizing and measuring a position of a center of the wafer using an optical unit connected to the measuring apparatus computer; recognizing and measuring a position of a wafer alignment mark using the optical unit, wherein the wafer alignment mark is formed on a boundary of a plurality of chips formed on the wafer and the position of the center of the wafer and the position of the wafer alignment mark are defined relative to the map; inputting measurement data comprising a measured position of a wafer overlay mark to the measuring apparatus computer, wherein the wafer overlay mark is separated from the wafer alignment mark; comparing the measurement data with the setup data; and, outputting an interlock control signal from the measuring apparatus computer if the measured position of the wafer overlay mark is outside of the allowable range, wherein the setup position corresponds to a position of a reticle overlay mark formed in a reticle of an exposure unit and comprises a first coordinate corresponding to a first axis and a second coordinate corresponding to a second axis; the setup position is defined relative to a position of a reticle alignment mark formed in the reticle; and, the allowable range is defined by first and second upper limits corresponding to the setup position and first and second lower limits corresponding to the setup position, wherein the first upper limit and the first lower limit each correspond to the first axis in a coordinate plane, and the second upper limit and the second lower limit each correspond to the second axis in the coordinate plane and orthogonal to the first axis, wherein: the first upper limit is about 0.02 mm greater than the first coordinate and the first lower limit is about 0.02 mm less than the first coordinate; and the second upper limit is about 0.02 mm greater than the second coordinate and the second lower limit is about 0.02 mm less than the second coordinate.