CPC G01B 11/272 (2013.01) [G01B 2210/56 (2013.01)] | 26 Claims |
1. A method for imaging overlay targets on a wafer comprising:
using a sensor to acquire images of overlay targets on a wafer while the wafer is in motion; and
accelerating and decelerating the wafer to move the overlay targets into alignment with the sensor between acquiring images of the overlay targets, wherein the wafer moves without stopping between acquiring the images of the overlay targets and accelerating and decelerating the wafer, and wherein accelerating and decelerating the wafer to move the overlay targets into alignment with the sensor between acquiring images of the overlay targets comprises:
linearly accelerating the wafer, wherein an acceleration of the wafer linearly increases; then
linearly decelerating the wafer, wherein an acceleration of the wafer linearly decreases; and then
linearly accelerating the wafer, wherein an acceleration of the wafer linearly increases.
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