| 摘要 |
A method for checking the accuracy of a measuring instrument used for overlay registration includes the steps of forming a plurality of sets of overlay marks on a calibration mask, each of the overlay marks consisting of an outer box and an inner box, the central point of the outer box being shifted by a predetermined amount relative to the cental point of the inner box. A photoresist layer is then coated atop a control wafer and exposed through the calibration mask. Subsequently, the control wafer is developed to transfer the pattern of the mask to the photoresist layer atop the control wafer. The degree of accuracy of the measuring instrument used for overlay registration can be checked and measured by first taking a deviation of a measured shift amount for each set, which is defined as a difference between the measured shift amount and a corresponding predetermined value, and then taking a mean value of these deviations for all sets.
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