Dual Pitch Lead Screw
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
A mechanical table for X-ray lithography is driven by a conventional lead screw, but has a soft flexure arrangement attached to it to provide both coarse and fine motion control. The coarse motion is desired for loading and unloading the mask and wafers, but a fine motion is needed as the mask-wafer gap is closed. A stepping motor drives the screw in a basic 200 counts per revolution or 10 microns per count. The table moves with this coarse movement until it contacts stop 1. A flexure 2, attached to the table, contacts the stop 1. At this point a second flexure 3, coupling the screw nut 4, to the stage top 5 begins to flex and the advance of the stage top 5 is now controlled not only by the advancement of nut 4 but also by the relative bending of flexures 2 and 3.