An apparatus for processing a semiconductor wafer is set forth. The apparatus comprises a processing bowl that defines a processing chamber. The processing bowl is in fixed alignment with a frame. A wafer support structure adapted to support at least one wafer is mounted for rotation within the processing chamber. A motor drive assembly is disposed exterior to the processing chamber and connected to rotate the wafer support. The motor drive assembly includes an electrically driven motor and at least one shock absorbing member connected between the electrically driven motor and the frame. The electrically driven motor preferably includes a rotor shaft that rotates about an axis of rotation. The shock absorbing member is adapted to elastically deform in substantially all directions perpendicular to the axis of rotation of the rotor shaft in response to vibrational forces having components perpendicular to the axis of rotation and, to a lesser degree, in directions parallel to the axis of rotation of the rotating shaft in response to vibrational forces having components parallel to the axis of rotation. In accordance with a further, independently unique aspect of the present invention, an aggressive seal is provided to prevent materials, such as processing fluids, from entering the motor in the region of the motor rotor. To this end, expulsion threads are provided at an end of the rotor shaft of the motor. A member substantially surrounds the expulsion threads at the end of the rotor. Together, the member defines a chamber with the rotor. Rotation of the rotor and threads assist in preventing foreign materials from entering the motor.