| CPC H01L 21/681 (2013.01) [G01B 11/24 (2013.01); G01B 11/26 (2013.01)] | 12 Claims |
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1. A method for detecting positions of wafers, comprising the following steps:
placing the wafer on a rotating table, and a contour of the wafer including an aiming feature;
driving, by a controller, the rotation table to rotate in a first direction at a first speed, so as to drive the wafer to rotate in the first direction at the first speed;
detecting, by a detector, the contour of the wafer rotating in the first direction at the first speed to provide a piece of contour data, corresponding to a respective currently-detected position on the contour, to the controller;
when the controller, according to the piece of contour data corresponding to rotation of the rotation table in the first direction at the first speed, determines that the aiming feature passes the detector in the first direction at the first speed, by the controller, driving the rotation table to rotate in a second direction at a second speed to drive the wafer to rotate in the second direction at the second speed, and the second direction being opposite to the first direction;
detecting, by the detector, the contour of the wafer rotating in the second direction at the second speed to provide a new piece of contour data, corresponding to a respective currently-detected position on the contour, to the controller;
when the controller, according to the piece of contour data corresponding to rotation of the wafer in the second direction at the second speed, determines that the aiming feature passes the detector in the second direction at the second speed, by the controller, stopping rotation of the rotation table and detection of the wafer to according to an accumulation of contour data and rotation angles corresponding to all the detected positions on the contour, estimate an eccentric position of the wafer and a position of the aiming feature;
estimating, by the controller, a total measured angle of the wafer according to the accumulation of contour data and the rotation angles corresponding to all the detected positions on the contour, and the total measured angle being an angle corresponding to a detected range on the contour of the wafer;
determining, by the controller, whether the total measured angle is greater than or equal to a first angle threshold;
estimating a deviation of a center of the wafer and an angular deviation of the aiming feature according to the accumulation of contour data and the rotation angles corresponding to all the detected positions on the contour by the controller after the rotation of the rotation table and the detection of the wafer are stopped; and
executing, by the controller, a first compensation scheme when the total measured angle is less than the first angle threshold, and the first compensation scheme comprising the following steps:
driving, by the controller, the rotation table to rotate in the first direction at the first speed again, so as to drive the wafer to rotate in the first direction at the first speed again;
detecting, by the detector, the contour of the wafer rotating in the first direction at the first speed again to provide a new piece of contour data, corresponding to a respective currently-detected position on the contour, to the controller; and
updating, by the controller, the total measured angle according to the accumulation of contour data and the rotation angles corresponding to all the detected positions on the contour to determine whether the updated total measured angle is greater than or equal to the first angle threshold,
wherein:
the respective piece of contour data is related to a distance from a rotation center of the rotation table to corresponding one of the detected positions on the contour;
when the controller, according to the contour data, determines that the aiming feature passes the detector in the second direction and the total measured angle is greater than or equal to the first angle threshold, the controller stops the rotation of the rotation table and the detection of the wafer; and
estimating the eccentric position of the wafer according to the accumulation of contour data and the rotation angles corresponding to all the detected positions on the contour comprises the following steps:
mapping a respective piece of contour data among the accumulation of contour data and the corresponding rotation angle into a respective piece of two-dimensional information;
simulating a circular curve corresponding to all the detected positions on the contour of the wafer according all the pieces of two-dimensional information; and
estimating a center of the circular curve as the eccentric position of the wafer.
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