Substrate transfer apparatus

A substrate transfer apparatus comprising:

• a base;
• a robot arm mounted on the base;
• an end effector provided at a tip of the robot arm and having a first tip portion and a second tip portion that are bifurcated;
• a light emitting unit configured to emit light from the first tip portion toward the second tip portion;
• a light receiving unit configured to convert detection light into an output value continuously changed depending on an amount of received light traveling through a space between the first tip portion and the second tip portion and incident on the second tip portion;
• and
• a control device controlling an operation of the robot arm,
• wherein the control device
• controls an operation of the robot arm so that light traveling through a tip of the end effector scans edges of a plurality of substrates accommodated in a front opening unified pod (FOUP), and
• compares shape patterns of a measured waveform of the output value continuously changed in the light receiving unit with shape patterns of a reference waveform for comparison according to a relative positional relationship between the light and the substrate during the operation of the robot arm and diagnoses at least one of a state of the substrate, a state of the FOUP, and a state of the end effector based on a comparison result.