by the pressure head to an auxiliary wafer processing station. The auxiliary processing station may include, for example, a station for cleaning the wafer and/or polishing head, a wafer unload station, or a wafer load station.
More recently, chemical-mechanical polishing (CMP) apparatus has been employed in combination with a pneumatically actuated polishing head. CMP apparatus is used primarily for polishing the front face or device side of a semiconductor wafer during the fabrication of semiconductor devices on the wafer. A wafer is xe2x80x9cplanarizedxe2x80x9d or smoothed one or more times during a fabrication process in order for the top surface of the wafer to be as flat as possible. A wafer is polished by being placed on a carrier and pressed face down onto a polishing pad covered with aspacer of elongated shape that has on a first surface a key for intimately engaging the slot opening in the hub shaft and on a second opposing surface a pin for intimately engaging a recess in the hub frame such that a rotational torque may be transferred from the hub frame to the hub shaft.
In the apparatus for transferring a torque from a hub frame to a hub shaft, the slot opening in the hub shaft may be provided in a rectangular-shape adapted for receiving a rectangular-shaped key on the first surface of the hub spacer, or provided in a trapezoidal-shape adapted for receiving a trapezoidal-shaped key on the first surface of the hub spacer. The hub frame may further include a slot recess in the center aperture