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High Resolution Verniers for Measuring Field Stitch And Pattern Over Lay

IP.com Disclosure Number: IPCOM000101353D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

McCord, MA: AUTHOR [+3]

Abstract

Disclosed is a method for measuring registration between two patterns with extremely high resolution in a simple and unambiguous manner. Each pattern contains one half of a test structure, the two halves together defining a set of lines of varying widths. The first line that fails to be defined indicates the relative placement accuracy of two patterns.

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High Resolution Verniers for Measuring Field Stitch And Pattern Over Lay

       Disclosed is a method for measuring registration between
two patterns with extremely high resolution in a simple and
unambiguous manner.  Each pattern contains one half of a test
structure, the two halves together defining a set of lines of varying
widths.  The first line that fails to be defined indicates the
relative placement accuracy of two patterns.

      Pattern registration is a major concern in present high
resolution integrated circuit lithography.  There are two common
types of registration - stitching between adjacent subfields that
occurs when the pattern is too large to be exposed with one field,
and overlay between levels when successive exposures are made one on
top of another.  Errors in registration are often measured with
vernier patterns, where lines on slightly different pitches are
butted up against each other, with each set being written in a
different exposure field.  A human operator then examines the pattern
under a microscope and, from the pair of lines that most nearly line
up, determines the registration error.

      However, as feature sizes decrease into the submicron range,
registration requirements become correspondingly more stringent, and
errors must be measured with accuracy better than 0.1 micrometer.
This becomes difficult to do with optical microscopes whose
resolution is limited to about 0.5 micrometer and the results can be
operator- de...