| 摘要 |
PURPOSE: An overlay measurement method is provided to improve overlay accuracy by constantly maintaining the distance between an overlay object layer and an overlay target using automatic focusing function of a sensor. CONSTITUTION: Each distance between an overlay object layer(4) and an overlay target(2) is sensed at each measuring position by using a sensor with automatic focusing function. The sensing signal transports to a stage motor. A stage of an overlay measuring unit compensates to +Z or -Z axis direction, thereby constantly maintaining the distance.
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