Browse Prior Art Database

Functional Inspection of Photomasks

IP.com Disclosure Number: IPCOM000104634D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Levenson, MD: AUTHOR

Abstract

Disclosed is a method of functional inspection of photomasks containing sub resolution features, phase shifts, serifs and other optical-resolution-enhancing structures not easily analyzed by conventional metrology.

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This is the abbreviated version, containing approximately 66% of the total text.

Functional Inspection of Photomasks

      Disclosed is a method of functional inspection of photomasks
containing sub resolution features, phase shifts, serifs and other
optical-resolution-enhancing structures not easily analyzed by
conventional metrology.

      The areal image projected by an optical system having the input
numerical aperture, pupil filling ratio, illumination spectrum, etc.
characteristic of a given lithography tool is made to fall on a
vidicon or orthicon type target.  The target material is optimized
for wide dynamic range, resolution and linear (or at lease
reproducible) response to the illumination pattern, rather than
sensitivity as is usually the case.  The imaging lens of the
inspection system produces an image of the same quality (but not
necessarily the same magnification) as the projection system and is
part of the vacuum system containing the target.  The imaging lens is
designed to simulate the lens of the projection camera.  The imaging
lens may be similar to the projection camera lens, or may be designed
according to the known scaling laws of optics as a simulating lens.

      A pattern of charges or voltages is produced on the target by
photemission or photoconductivity.  That pattern then modulates the
reflection, secondary emission or scattering of an scanning electron
microscope (SEM) beam incident on the target.  The current is
collected by the SEM electron multiplier system.  The charge or
potential pattern on the...