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SEMI P21-92 © SEMI 1992, 2003 2 3.4 Pattern Stitching Accuracy 3.4.1 Definition • Po sition errors at the stitchin g boundary of writing fields, stripes, and shots. 3.4.2 Expression • |average value| 1 + 3 σ µm (X and Y …

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SEMI P21-92 © SEMI 1992, 2003 1
SEMI P21-92 (Reapproved 0703)
GUIDELINES FOR PRECISION AND ACCURACY EXPRESSION FOR
MASK WRITING EQUIPMENT
This guideline was technically approved by the Global Micropatterning Committee and is the direct
responsibility of the Japanese Micropatterning Committee. Current edition approved by the Japanese
Regional Standards Committee on April 28, 2003. Initially available at www.semi.org June 2003; to be
published July 2003. Originally published in 1992.
1 Purpose
1.1 This guideline describes general requirements
concerning precision and accuracy expression of mask
writing equipment. Writing accuracy of the mask
writing equipment is evaluated by measuring a written
mask and is affected greatly by process conditions to be
carried out. Therefore, the writing conditions are to be
agreed upon by the user and supplier.
2 Scope
NOTICE: This standard does not purport to address
safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety and health practices and determine
the applicability of regulatory or other limitations prior
to use.
3 Precision and Accuracy Expression Items,
Definitions, Measurement, and Requirements
3.1 Minimum Pattern
3.1.1 Definition
• The minimum line and space pattern and minimum
pattern which is possible to be separated.
3.1.2 Expression
• SEM photograph
3.1.3 Measurement
• SEM photograph of the resist pattern or the chrome
pattern.
3.2 Pattern Dimension Precision and Accuracy
3.2.1 Definition
• Critical Dimension (CD) variation and deviation of
written pattern from designed value.
3.2.2 Expression
• Deviation of measured mean value to design value
(∆l:µm) and variations (3 σ:µm).
• Measured area and number of sampling point
should be clearly described.
3.2.3 Measurement
• Optical CD measurement
• Electron beam CD measurement
• CD measurement done by self-diagnostic feature of
writing equipment.
3.2.4 Requirement
• Width of a long line pattern in X and Y direction
should be measured.
• Pattern types are isolated pattern; 1:1 line and
space pattern or 1:2 line and space pattern.
• The line width to be measured is not specified, but
at least three different line widths should be
measured.
• Examples of patterns are shown in Figures 1 and 2.
3.3 Overlay Accuracy
3.3.1 Definition
• Relative deviation of pattern position between two
masks.
3.3.2 Expression
• 3σ:µm (X and Y direction separately)
• Measured area and number of sampling points
should be clearly described.
3.3.3 Measurement
• Optical coordinates measurement
• Electron beam coordinates measurement
• Coordinates measurement done by self-diagnostic
feature of writing equipment.
3.3.4 Requirement
• The pattern should be cross or L mark. Uniform
rotation error in measurement should be subtracted
from the measurement result.
• Overlay accuracy between different cassette should
be clearly described. An example of a pattern is
shown in Figure 3.
SEMI P21-92 © SEMI 1992, 2003 2
3.4 Pattern Stitching Accuracy
3.4.1 Definition
• Position errors at the stitching boundary of writing
fields, stripes, and shots.
3.4.2 Expression
• |average value| 1 + 3 σµm (X and Y direction
separately) measured area and number of sampling
points should be clearly described.
3.4.3 Measurement
• Optical coordinates measurement
• Electron beam coordinate measurement
• Coordinates measurement done by self-diagnostic
feature of writing equipment.
• Vernier measurement
• Boundary measurement by SEM image
3.4.4 Requirement
• The pattern should be cross or L marks in both
sides adjacent to the stitching boundary for
coordinate measurement.
• When the optical microscope is used for
measurement, the vernier pattern should be used.
4 Notice
4.1 The following subjects should be agreed upon
beforehand between users and makers in order to
evaluate the above-mentioned writing precision and
accuracy item.
4.1.1 Process Requirements
• Resist Materials
• Coating Condition
• Development Condition
• Process Sequence
• Mask Substrate and Chrome Thin Film Materials
4.1.2 Test Pattern
4.1.3 Measurement Procedure
5 Others
5.1 The following items are not specified in these
guidelines, still it is preferable that these items are
agreed upon beforehand between user and supplier.
5.1.1 Pattern coordinates
5.1.2 Pattern position accuracy
5.1.3 Long-term stability of accuracy
5.1.4 Particles
SEMI P21-92 © SEMI 1992, 2003 3
Figure 1