A method of detecting the position of a wafer

摘要

A wafer (12) is transferred between a processing position and a loadlock chamber (101) by a robot-driven gripper arm (22) rotating about a vertical axis (23). The loadlock includes three photovoltaic optical sensors, one (107) determining that the gripper arm is in the hand-off position and two (108, 109) around the edges of the wafer determining its position. A fourth optical detector (110) detects a hole (115) to determine a vertical position of the loadlock platen. Independent claims are also included for the following: (a) a method of detecting the position of a wafer of a known diameter by measuring the intensity of light falling on two sensors located around the edges of the wafer; (b) a method of calibrating an apparatus for processing wafers by sensing the intensity of light from a sensor when a gripper arm is in a hand-off position and a wafer is in a central position determined by two other sensors and operating the apparatus by returning to these known positions; (c) a system for detecting that a loadlock platen and a gripper arm are correctly vertically-positioned using a sensor detecting a hole located on the gripper (d) and a system for calibrating and controlling an ion implantation process.