Browse Prior Art Database

Emulation to Eliminate Character of a Maskmaking Tool

IP.com Disclosure Number: IPCOM000037889D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Weber, EV: AUTHOR

Abstract

This technique uses software to provide a rapid correction of actual table position in semiconductor maskmaking tools to match a master grid. The system table would emulate either a nominally perfect master or the distortion of another system.

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Emulation to Eliminate Character of a Maskmaking Tool

This technique uses software to provide a rapid correction of actual table position in semiconductor maskmaking tools to match a master grid. The system table would emulate either a nominally perfect master or the distortion of another system.

Extreme accuracies are required for semiconductor masks which exceed the capabilities of normal mechanical tolerances. Precision tables generally use laser measuring systems which determine distance by monitoring the phase shift of light reflected from a mirror mounted on the stepping table. Errors which occur are quite repeatable so that conventional mask fabrication is accomplished by exposing all masks which are to overlay using one mechanical stepping table. Since replacement and additional masks can only be made with the same table this means no major maintenance may be performed on the table and it precludes backup. Additionally, measurement of masks must be done to an historical reference rather than an ideal reference, such as the National Bureau of Standards. The complications lead to very careful fixturing and slow operations.

All masks can be made to an ideal reference by eliminating the repeating character of the stepping table. While this may be accomplished by redefining the address at which the individual exposures which form the mask are made, it is not easy to implement since only one family of masks uses a given set of addresses. Since there are numerou...