Abstract: A substrate handling system is provided with a robot having the dual function of a removing and replacing substrate-containing pod doors and load lock chamber doors, and of transporting the substrates between the pods and various processing stations. The robot is equipped with an end effector having sockets into which interchangeable tools for implementing the various functions are removably mounted. The tools are retrieved from respective parking locations disposed within the system micro environment, and automatic interchangeability of the tools is facilitated by a novel socket mechanism which engages and disengages the tools to the robot arm without introducing contaminants into the micro environment.