ASTM E766-14(2019)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E766 −14 (Reapproved 2019)
Standard Practice for
Calibrating the Magnification of a Scanning Electron
Microscope
This standard is issued under the fixed designation E766; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Determine the Precision of a Test Method
2.2 ISO Standard:
1.1 This practice covers general procedures necessary for
ISOGuide30:1992TermsandDefinitionsUsedinConnec-
the calibration of magnification of scanning electron micro-
tion with Reference Materials
scopes. The relationship between true magnification and indi-
cated magnification is a complicated function of operating
3. Terminology
conditions. Therefore,thispracticemustbeappliedtoeachset
3.1 Definitions:
of standard operating conditions to be used.
3.1.1 For definitions of metallographic terms used in this
1.2 The values stated in SI units are to be regarded as
practice see Terminology E7.
standard. No other units of measurement are included in this
3.1.2 The definitions related to statistical analysis of date
standard.
appearing in Practice E177, Terminology E456, and Practice
1.3 This standard does not purport to address all of the
E691 shall be considered as appropriate to the terms used in
safety concerns, if any, associated with its use. It is the
this practice.
responsibility of the user of this standard to establish appro-
3.2 Definitions of Terms Specific to This Standard:
priate safety, health, and environmental practices and deter-
3.2.1 calibration—the set of operations which establish,
mine the applicability of regulatory limitations prior to use.
under specified conditions, the relationship between magnifi-
1.4 This international standard was developed in accor-
cation values indicated by the SEM and the corresponding
dance with internationally recognized principles on standard-
magnificationvaluesdeterminedbyexaminationofareference
ization established in the Decision on Principles for the
material.
Development of International Standards, Guides and Recom-
3.2.2 calibration method—a technical procedure for per-
mendations issued by the World Trade Organization Technical
forming a calibration.
Barriers to Trade (TBT) Committee.
3.2.3 certified reference material—reference material, ac-
companied by a certificate, one or more of whose property
2. Referenced Documents
values are certified by a procedure which establishes its
2.1 ASTM Standards:
traceability to an accurate realization of the unit in which the
E7Terminology Relating to Metallography
property values are expressed, and for which each certified
E29Practice for Using Significant Digits in Test Data to
value is accompanied by an uncertainty at a stated level of
Determine Conformance with Specifications
confidence (see ISO Guide 30:1992).
E177Practice for Use of the Terms Precision and Bias in
3.2.4 pitch—the separation of two similar structures, mea-
ASTM Test Methods
sured as the center to center or edge to edge distance.
E456Terminology Relating to Quality and Statistics
E691Practice for Conducting an Interlaboratory Study to
3.2.5 reference material—a material or substance one or
more of whose property values are sufficiently homogeneous,
stable, and well established to be used for the calibration of an
This practice is under the jurisdiction of ASTM Committee E04 on Metallog-
apparatus, the assessment of a measurement method, or for
raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray and
assigning values to materials (see ISO Guide 30:1992).
Electron Metallography.
Current edition approved Nov. 1, 2019. Published November 2019. Originally
3.2.6 reference standard—a reference material, generally of
ε1
approved in 1980. Last previous edition approved in 2014 as E766–14 . DOI:
the highest metrological quality available, from which mea-
10.1520/E0766-14R19.
surements are derived.
See Annex A1.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E766−14 (2019)
3.2.7 traceability—the property of a result of a measure- 5.4.4 Made of or coated with electrically conductive, elec-
ment whereby it can be related to appropriate international/ tron beam stable materials, and
national standards through an unbroken chain of comparisons.
5.4.5 Made of materials which can be cleaned to remove
contamination which occurs during normal use.
3.2.8 verification—confirmation by examination and provi-
sion of evidence that specified requirements have been met.
5.5 Undertypicalusesomecontaminationofthecalibration
specimen should be expected. When cleaning becomes neces-
4. Significance and Use
sary always follow the manufacturer’s instructions. Improper
handling, especially during cleaning, may invalidate the cali-
4.1 Proper use of this practice can yield calibrated magni-
bration specimen’s certificate of accuracy or traceability and
ficationswithprecisionof5%orbetterwithinamagnification
require re-certification. Care should be taken to prevent the
range of from 10 to 50 000X.
standard from sustaining mechanical damage which may alter
4.2 The use of calibration specimens traceable to
the standard’s structure.
international/national standards, such as NIST-SRM 484, with
5.6 The facility using this practice shall have arrangements
this practice will yield magnifications accurate to better than
for the proper storage, handling, and use of the calibration
5% over the calibrated range of operating conditions.
specimen(s) which should include but is not limited to:
4.3 Theaccuracyofthecalibratedmagnifications,ordimen-
5.6.1 Storage in a desiccating cabinet or vacuum container,
sional measurements, will be poorer than the accuracy of the
5.6.2 Usingfingercots,cleanroomglovesortweezerswhen
calibration specimen used with this practice.
handling, and
4.4 For accuracy approaching that of the calibration speci-
5.6.3 Restricting its use to calibration only, unless it can be
men this practice must be applied with the identical operating
shownthattheperformanceofthecalibrationspecimenwillbe
conditions (accelerating voltage, working distance and magni-
unaffected by such use.
fication) used to image the specimens of interest.
5.7 Thefacilityusingthispracticeshallestablishaschedule
4.5 It is incumbent upon each facility using this practice to
for verification of the calibration specimen(s), where verifica-
define the standard range of magnification and operating
tion should include but is not limited to:
conditions as well as the desired accuracy for which this
5.7.1 Visualandmicroscopicalinspectionforcontamination
practice will be applied. The standard operating conditions
and deterioration which may affect performance,
must include those parameters which the operator can control
5.7.2 Photomicrographic comparison (and documentation)
including: accelerating voltage, working distance,
of the present state of the calibration specimen(s) to the
magnification, and imaging mode.
original state, and
5.7.3 Validation or re-certification of calibration speci-
5. Calibration Specimen
men(s) distance intervals against other reference standards or
5.1 Theselectionofcalibrationspecimen(s)isdependenton
certified reference materials.
the magnification range and the accuracy required.
6. Procedure
5.2 The use of reference standards, reference materials, or
certified reference materials traceable to international/national
6.1 Mounting of the calibration specimen.
standards (NIST, Gaithersburg, MD; NPL,Teddington, UK; or
6.1.1 Visually inspect the calibration specimen surface for
JNRLM, Tsukuba, Japan) calibration specimens is recom-
contamination and deterioration which may affect perfor-
mended. However, the use of internal or secondary reference
mance.Removeanydustorloosedebrisusingextracarenotto
materials validated against reference standards or certified
damage the specimen surface. One safe method is to use clean
reference materials may be used with this practice.
dry canned air to remove the loose surface debris.
5.3 Where traceability to international or national standards
6.1.2 Ensure good electrical contact by following the SEM
is not required, internal reference materials, verified as far as
and calibration specimen manufacturers’ directions for mount-
technically practicable and economically feasible, are appro-
ing. In some instances the use of a conductive cement may be
priate as calibration specimens and may be used with this
required.
practice.
6.1.3 Mountthecalibrationspecimenrigidlyandsecurelyin
the SEM specimen stage to minimize any image degradation
5.4 The most useful calibration specimens should have the
caused by vibration.
following characteristics:
5.4.1 A series of patterns allowing calibration of the full
6.2 Evacuate the SEM chamber to the desired or standard
field of view as well as fractional portions of the field of view
working vacuum.
over the range of standard magnifications. Suitable standards
6.3 Turn OFF the tilt correction and scan rotation circuits.
allow for the pattern “pitch” to be measured,
These circuits should be calibrated independently.
5.4.2 Pitch patterns allowing calibration in both X and Y
without having to rotate the sample or the raster,
6.4 Set the specimen tilt to 0° such that the surface of the
5.4.3 Made from materials which provide good contrast for calibration specimen is perpendicular to the electron beam. A
the various imaging modes, especially secondary electron and technique for checking specimen surface perpendicularity is to
backscatter electron imaging. observetheimagefocusasthespecimenistranslatedtwicethe
E766−14 (2019)
picture width in the X or Y direction. The change of image 6.11 Recording CRT calibration method (for older SEMs).
focusshouldbeminimalatanominalmagnificationof1000X. 6.11.1 Photograph the field used in 6.10 with sufficient
signal to noise ratio and image contrast to allow for accurate
6.5 Adjust the accelerating voltage, working distance, and
measurements.
magnification to the desired or standard operating conditions.
6.11.2 Allowsufficienttimeforthephotographicmaterialto
6.6 The instrument should be allowed to fully stabilize at
stabilize prior to measurement. This will minimize the effects
the desired operating conditions. The time required will be
of dimensional changes in the film caused by temperature and
pre-determined by the facility using this practice.
humidity.
6.11.3 Measure and record the pitch distance (D) between
6.7 Minimize residual magnetic hysteresis effects in the
two of the fiducial markings (in mm 6 0.5 mm) which are
lenses by using the degauss feature, cycling lens circuits
separatedbythelargestspacinginthephotomicrographforthe
ON-OFF-ON two or three times, or follow manufacturers
best precision.
recommendations.
6.11.4 Itisrecommendedthatthefiducialmarkingsusedfor
6.8 Adjust the image of the calibration specimen on the
thepitchmeasurementbeatleast10mmfromthephotoedges
viewing display.
to minimize edge distortion effects.
6.8.1 Bringtheimageofthespecimenintosharpfocus.The
6.11.5 If the measurement pattern consists of lines which
sample working distance should be pre-selected to determine
span the length or width of the photomicrograph, then repeat
magnification accuracy since different working distances may
the measurement in 6.11.3 at least three times at locations
have different magnification error
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