Robot having a centering and flat finding means

DETAILED DESCRIPTION One aspect of the present invention provides a wafer handling robot which does not require a second mechanism for performing the task of pre-alignment.
Preferred robots according to this aspect of the invention use the moving elements of the wafer handling robot which perform the wafer handling tasks to perform the tasks of centering and notch or flat finding.
The robot has been designed to incorporate sufficient intelligence and hardware to eliminate the need for a separate pre-alignment capability.
The robot is a cylindrical coordinate robot, having a vertical axis Z, a rotational axis theta and at least one radial axis R.
The robot uses these degrees of freedom to perform the task of centering and notch or flat finding as well as the task of pre-alignment.
One aspect of the present invention provides a cylindrical coordinate robot for performing the task of centering and notch or flat finding of a wafer as well as the task of pre-alignment.
The cylindrical coordinate robot includes a frame, at least one hand operatively mounted to the frame, a chuck having a vertical axis mounted to the frame, and means for moving at least one of the hands and the chuck relative to the frame so that the hand either places a wafer on the chuck or removes a wafer from the chuck and so that the hand moves relative to the chuck in a circumferential direction also referred to as the "theta"direction around the vertical axis of the chuck while a wafer is disposed on the chuck.
The robot further includes a sensor attached to the hand for detecting the radial position of the wafer edge at various circumferential positions about the vertical axis of the chuck.
Such robot uses the movement of the hand to both place the wafer and to determine the position of the wafer on the chuck.
The means for moving may include means for moving the hand relative to the frame so that the hand orbits around the vertical axis of the chuck in the theta direction while the chuck does not rotate around said vertical axis The means for moving the hand may further include means for moving said hand in radial or R directions towards or away from the vertical axis of the chuck while the hand is in each of a plurality of circumferential positions relative to the chuck