US Patent 9978631 Wafer pick-and-place method and system

A wafer pick-and-place method and system is provided. During the wafer pick-and-place operation, the distance between the fork of the robot and the target wafer is detected to determine whether the robot will collide with the target wafer. Furthermore, the tilted angle of the target wafer relative to the fork is calculated to determine whether the wafer will slip off. If collision or wafer slippery may occur, the pick-and-place operation is stopped. Therefore, wafer damages due to unexpected contact between the fork and the wafer can be avoided, and wafer handling safety can be improved.