As a key part of the photo-etching facility, the wafer prealigner uses mechanical or optical aligning method to save the time and guarantee the quality of manufacturing. In this paper, a new wafer prealigner is proposed based on the mass center calculation method. The mass center is measured by a reflection-style laser sensor from the wafer’s radial direction, and the position is measured by the notch angle detection using the penetration-style laser senor. A dynamic error compensation method is applied to eliminate the radial runout and wobble of the rotary stage, which have effects on measuring the wafer’s mass center. The accuracy is improved through two steps: firstly, a coarse alignment is made by adjusting the mass center; secondly, a precise alignment is processed by aligning the wafer’s notch. Experiments show that the accuracy of the wafer prealigner satisfied the system requirement.
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