Substrate transferring device

Abstract

A method for operating a substrate transferring device that includes a substrate container holding at least two substrates stacked vertically, a hand having two fingers, a manipulator, and a controller. A mapping device detects a vertical position of a higher substrate, and a substrate detector measures a distance to a principal surface of the substrate. The controller moves the hand to a position below the detected vertical position and then advances the hand to pick up the higher substrate. During forward movement, the substrate detector acquires at least three consecutive, linearly aligned distance measurements along a front-and-rear direction. Based on a relationship among the measurements, the controller determines whether the principal surface of the higher substrate is warped. If warpage is detected, the controller predicts a possibility of collision between the hand and the substrate and withdraws the hand to avoid collision.