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Micro-Characterization of Edges with Diffracted and Scattered Light

IP.com Disclosure Number: IPCOM000116562D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Wagner, D: AUTHOR

Abstract

Disclosed is a light optics method which allows to determine the angle of slope and the roughness of bevelled edges of reticle or mask patterns by separately measuring and using the difference between the light diffracted at the bevelled edge and the light scattered by the surface roughness.

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Micro-Characterization of Edges with Diffracted and Scattered Light

      Disclosed is a light optics method which allows to determine
the angle of slope and the roughness of bevelled edges of reticle or
mask patterns by separately measuring and using the difference
between the light diffracted at the bevelled edge and the light
scattered  by the surface roughness.

      Fig. 1 is a planview of a symmetrical arrangement with four
detectors D1, D2, D3 and D4 comprising photo diodes or
photoconductors connected to a multiplier.  This arrangement may be
used for characterizing edges in the x- or y-direction.  A portion of
the diffracted and scattered light falls onto the four detectors and
the rest is destroyed in a light trap.  Whereas small particles (>100
nm) uniformly scatter the impinging light into all directions, a
bevelled edge diffracts the impinging light into only small angle
areas.  This typical scattering and diffraction characteristic is
also shown in Fig. 1.

      The optimal detection of the slope angle requires the detector
to be installed normal to the edge direction.  Edges with different
slope angles will differently diffract and guide the light onto the
symmetrically arranged detectors D1 and D2.  A differential
connection of the detectors D1 and D2 eliminates the micro-roughness
of the edge which symmetrically affects the measuring result.

      For detecting the scattered light caused by the micro-roughness
of the edge the detector...