The present invention generally relates to an end effector that utilizes a
gripping mechanism to grip a peripheral edge of the wafer and secure the
wafer to the end effector. In one embodiment, the gripping mechanism
includes a pair of gripper arms that pivot between a wafer-loading
position and a wafer-engaging position. In another embodiment, an active
plunger moves linearly between the wafer-loading and wafer-engaging
positions. Both the gripper arms and the plunger device are driven by a
motor assembly. A force feedback system monitors the force the gripping
mechanism exerts on the wafer and, based on the amount of force, controls
the operation of the motor assembly to dynamically adjust the position of
the gripping mechanism.