Browse Prior Art Database

Fabrication of a Focus Monitor for Photomasks

IP.com Disclosure Number: IPCOM000115417D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Wagner, A: AUTHOR

Abstract

A method of fabricating a focus monitor on a production photomask is disclosed. The focus monitor provides a method of monitoring the accuracy of the focus of an optical printing tool used in the manufacture of integrated circuits. The structure and use of a of the SPIE volume 2197.

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Fabrication of a Focus Monitor for Photomasks

      A method of fabricating a focus monitor on a production
photomask is disclosed.  The focus monitor provides a method of
monitoring the accuracy of the focus of an optical printing tool used
in the manufacture of integrated circuits.  The structure and use of
a of the SPIE volume 2197.

      The focus monitor utilizes a pattern of chrome lines and phase
shifters to produce a measurable translation in the printed image of
the chrome lines as the focus varies.  The current approach to
fabricating this focus monitor on a photomask requires additional
electron beam or optical patterning steps and reactive ion etching of
a fabricated photomask.  The new method disclosed here uses a focused
ion beam to directly etch the quartz in a localized region thereby
forming the phase shifters.

      The most desirable approach is to add chrome bars to the
original photomask design, for example in the kerf area.  This would
add no extra processing or cost to the photomask at this stage.  A
focused ion beam would then be directed at the quartz areas between
the chrome bars to selectively remove the quartz, thus forming the
required phase shifters.  By simultaneously exposing the ion
irradiated area to XeF2 vapor, several advantages are obtained.
First, the etch rate of the quartz is increased by a factor of 10
thereby decreasing the etch time required.  Second, the gallium stain
induced by the ion beam is also reduced b...