Abstract: In the electron beam lithographic system disclosed herein, a semiconductor wafer to be exposed is carried on an air bearing puck which is, on both sides, supported or located by balanced annular regions of air pressure. These annular supporting regions surround central evacuated regions which are also balanced so that the puck is not subject to large bending forces. Accordingly, the puck can be constructed to light-weight materials facilitating rapid and precise positioning of the semiconducter wafer with respect to an E-beam generating column.

Abstract: A linear actuator for converting rotary motion to linear motion including an elongated rotary threadless shaft and a rider assembly mounted for movement axially of the shaft and carrying rollers mounted for rotation about their respective axes with their surface in frictional contact with the shaft. The roller's axes are disposed at an acute angle with respect to the shaft so that as the shaft is rotated the rider assembly will move along the shaft and carry with it such parts to which it may be attached.