Substrate transfer apparatus and method for calculating positional relationship between substrate transfer robot and substrate placement portion

A substrate transfer apparatus comprising:

• a substrate transfer robot provided with a robot reference axis and having an object detection sensor for detecting an object obstructing a detection area, and a robot arm for moving the object detection sensor in a plane perpendicular to an axial direction of the robot reference axis;
• a substrate placement portion having a target to be detected by the object detection sensor, the substrate placement portion being configured to rotate about a rotation axis extending in parallel to the axial direction;
• and
• a controller configured to control operations of the substrate transfer robot and the substrate placement portion, wherein
• the controller is programmed to perform the following:
• operate the substrate transfer robot and the substrate placement portion so as to detect a part of a surface of the target that is located on an inner circumferential side of a predetermined circle using the object detection sensor at a plurality of rotation positions,
• wherein the predetermined circle is centered on the rotation axis and passes through the target, and
• wherein at least one of a rotation position of the target about the rotation axis and a rotation position of the detection area about the robot reference axis is changed;
• operate the substrate transfer robot so as to:
• (i) move the detection area toward a rotation axis side from a robot reference axis side with respect to the target, to perform preliminary detection for the target,
• (ii) further move the detection area toward the rotation axis side until the target is no longer detected, and
• (iii) move the detection area toward the robot reference axis side from the rotation axis side with respect to the target, to detect the target,
• calculate a quantity correlated with an index length representing a distance from the robot reference axis to the target when the target is detected by the object detection sensor, for each of the plurality of rotation positions;
• and
• calculate a positional relationship between the robot reference axis and the rotation axis on the basis of, among the plurality of rotation positions, the one at which the quantity correlated with the index length is maximized or minimized.