CHEMICAL MECHANICAL POLISHING TOOL WITH ROBOT ACCESS TO CASSETTES

A semiconductor fabrication system includes a chemical mechanical polishing system, a cassette holding area enclosed by a wall and having a door openable by an operator to place one or more cassettes into the cassette holding area, a robot configured to transfer substrates between a cassette in the cassette holding area to the chemical mechanical polishing system, a computer controller configured to cause the robot to move to a home position, a circuit breaker in a power supply line to the robot, a door sensor to detect whether the door is open, a robot presence sensor to detect whether the robot is in the home position, and control circuitry configured to receive signals from the door sensor and the robot presence sensor and cause the circuit breaker to cut power to the robot if the door is open and the robot is not in the home position.