Browse Prior Art Database

Dual Pitch Lead Screw

IP.com Disclosure Number: IPCOM000043159D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Wilson, AD: AUTHOR

Abstract

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.

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Dual Pitch Lead Screw

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. If flexure 3 is "soft" and 2 is "stiff", then the nut motion is demagnified. The demagnification can be varied from 2 to over 10. Thus a basic 10-micron per step stage can be converted to 1-micron per step over a certain range, such as setting the gap between mask and wafer in X-ray lithography.

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