Abstract: Disclosed is an X-Y table for positioning semiconductor workpieces in a vacuum environment with a high degree of speed and accuracy. The X and Y prime movers are mounted on adjacent external surfaces of the vacuum chamber. The first motor associated with the drive in the Y direction seals with an O-ring onto the front surface of the chamber. A second motor associated with the X drive is fixedly mounted to one of the sides of the chamber. The lower stage providing motion in the Y direction has a single degree of freedom relative to the vacuum chamber. The upper stage providing motion in the X direction is connected to the lower Y stage and has two degrees of freedom relative to the vacuum chamber. The entire X-Y table assembly is mounted on rails in parallel with the Y direction of motion such that by removing the front wall of the vacuum chamber, the entire assembly may be removed for repair and/or maintenance. By such modular replacement, the entire E-beam tool can resume operation.