Browse Prior Art Database

Multiple Exposer Calibration Curves for Optical Measurement Tools

IP.com Disclosure Number: IPCOM000102031D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 80K

Publishing Venue

IBM

Related People

Fetzer, B: AUTHOR [+3]

Abstract

Current chip linewidth tolerances and submicron dimensions have neces- sitated a new measurement strategy using a multipoint calibration curve using a change in stepper exposer dose to measure submicron dimensions.

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This is the abbreviated version, containing approximately 52% of the total text.

Multiple Exposer Calibration Curves for Optical Measurement Tools

       Current chip linewidth tolerances and submicron
dimensions have neces- sitated a new measurement strategy using a
multipoint calibration curve using a change in stepper exposer dose
to measure submicron dimensions.

      Some video-based measurement tools provide a multipoint
calibration curve generated for each measured level or sample type.
Each curve is used in a measurement program. This calibration removes
operator influence on measurements.

      An accurate calibration curve needs at least one 90-degree SEM
of a particular linewidth ("actual" linewidth).  The measurement tool
"observes" this value and an offset is generated between the actual
and observed values.

      Three different curves can be used as follows:
           a)  single-point calibration line drawn through origin
   b)  two-point calibration line (two calibrated points are used to
generate a line)
           c)  multipoint calibration curve where many points needed

      More calibrated points improve accuracy of linewidth
measurements. Usually, measurements are taken to monitor only the
critical dimension. The calibration curve is generated about this
point.

      In dealing with large linewidth dimensions, a variety of
geometry sizes are used to generate calibration curves.

      In measuring submicron dimensions a multipoint calibration
curve is generated using the same mask geometry but varying the
stepper exposer dose.  To maintain consistency, the change in exposer
dose cannot vary the photoresist or etched profile dramatically.

      Linewidth measurements taken acr...