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Method for Aligning Objects

IP.com Disclosure Number: IPCOM000119779D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 59K

Publishing Venue

IBM

Related People

Krakow, W: AUTHOR

Abstract

Usually alignment of objects is achieved by optical interferometry techniques. This is particularly true for electron beam and optical lithography techniques. It is also possible to position the beam in a lithographic instrument and check it against a desired location or fiducial mark. It is not clear, however, that any method other than operator adjustment is possible to correctly align a wafer.

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This is the abbreviated version, containing approximately 60% of the total text.

Method for Aligning Objects

      Usually alignment of objects is achieved by optical
interferometry techniques.  This is particularly true for electron
beam and optical lithography techniques.  It is also possible to
position the beam in a lithographic instrument and check it against a
desired location or fiducial mark. It is not clear, however, that any
method other than operator adjustment is possible to correctly align
a wafer.

      To provide an improved alignment procedure, a method is
described in which an object which has fiducial marks can be aligned
precisely without operator intervention.  This method will allow a
vector offset to be determined under computer control which can
subsequently be used to adjust the object position for alignment.

      The drawing schematically illustrates the method, which uses
fiducial mark 10 on the object and an image of two triangular shapes
12, 14.  The triangles are in a separate image and arranged such that
one straight portion 10A of the fiducial mark intersects triangle 12
and the other straight portion 10B intersects triangle 14.  The ANDed
image is then taken between the fiducial mark image and the triangle
image with only the cross hatched regions 16A, 16B then being
visible.  Depending on the area included in the ANDed image of each
triangle, the position of the fiducial mark bars 10A, 10B are
determined.  For each triangle a specific area swept out would be the
correct alignment position.  For too...