1、Designation: E 766 98 (Reapproved 2008)1Standard Practice forCalibrating the Magnification of a Scanning ElectronMicroscope1This standard is issued under the fixed designation E 766; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTE3.1.2 and 6.9.2 were editorially corrected in June 2008.1. Scope1.1 This practice covers general procedures neces
3、sary forthe calibration of magnification of scanning electron micro-scopes. The relationship between true magnification and indi-cated magnification is a complicated function of operatingconditions.2Therefore, this practice must be applied to each setof standard operating conditions to be used.1.2 T
4、he values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pri
5、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E7 Terminology Relating to MetallographyE29 Standard Practice For Using Significant Digits in TestData to Determine Conformance with SpecificationsE 177
6、Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO Guide 30: 1992 Terms and Definitions Used in Con-nection with
7、Reference Materials43. Terminology3.1 Definitions:3.1.1 For definitions of metallographic terms used in thispractice see Terminology E7.3.1.2 The definitions related to statistical analysis of dateappearing in Practice E 177, Terminology E 456, and PracticeE 691 shall be considered as appropriate to
8、 the terms used inthis practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrationthe set of operations which establish,under specified conditions, the relationship between magnifi-cation values indicated by the SEM and the correspondingmagnification values determined by examinatio
9、n of a referencematerial.3.2.2 calibration methoda technical procedure for per-forming a calibration.3.2.3 certified reference materialreference material, ac-companied by a certificate, one or more of whose propertyvalues are certified by a procedure which establishes itstraceability to an accurate
10、realization of the unit in which theproperty values are expressed, and for which each certifiedvalue is accompanied by an uncertainty at a stated level ofconfidence (see ISO Guide 30:1992).3.2.4 pitchthe separation of two similar structures, mea-sured as the center to center or edge to edge distance
11、.3.2.5 reference materiala material or substance one ormore of whose property values are sufficiently homogeneous,stable, and well established to be used for the calibration of anapparatus, the assessment of a measurement method, or forassigning values to materials (see ISO Guide 30:1992).3.2.6 refe
12、rence standarda reference material, generally ofthe highest metrological quality available, from which mea-surements are derived.1This practice is under the jurisdiction of ASTM Committee E04 on Metallog-raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray andElectron Metallography
13、.Current edition approved June 15, 2008. Published June 2008. Originallyapproved in 1980. Last previous edition approved in 2003 E 766 98(2003).2See Annex A1.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A
14、STMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
15、hohocken, PA 19428-2959, United States.3.2.7 traceabilitythe property of a result of a measure-ment whereby it can be related to appropriate international/national standards through an unbroken chain of comparisons.3.2.8 verificationconfirmation by examination and provi-sion of evidence that specifi
16、ed requirements have been met.4. Significance and Use4.1 Proper use of this practice can yield calibrated magni-fications with precision of 5 % or better within a magnificationrange of from 10 to 50 000X.4.2 The use of calibration specimens traceable tointernational/national standards, such as NIST-
17、SRM 484, withthis practice will yield magnifications accurate to better than5 % over the calibrated range of operating conditions.4.3 The accuracy of the calibrated magnifications, or dimen-sional measurements, will be poorer than the accuracy of thecalibration specimen used with this practice.4.4 F
18、or accuracy approaching that of the calibration speci-men this practice must be applied with the identical operatingconditions (accelerating voltage, working distance and magni-fication) used to image the specimens of interest.4.5 It is incumbent upon each facility using this practice todefine the s
19、tandard range of magnification and operatingconditions as well as the desired accuracy for which thispractice will be applied. The standard operating conditionsmust include those parameters which the operator can controlincluding: accelerating voltage, working distance, magnifica-tion, and imaging m
20、ode.5. Calibration Specimen5.1 The selection of calibration specimen(s) is dependent onthe magnification range and the accuracy required.5.2 The use of reference standards, reference materials, orcertified reference materials traceable to international/nationalstandards (NIST, Gaithersburg, MD; NPL,
21、 Teddington, UK; orJNRLM, Tsukuba, Japan) calibration specimens is recom-mended. However, the use of internal or secondary referencematerials validated against reference standards or certifiedreference materials may be used with this practice.5.3 Where traceability to international or national stand
22、ardsis not required, internal reference materials, verified as far astechnically practicable and economically feasible, are appro-priate as calibration specimens and may be used with thispractice.5.4 The most useful calibration specimens should have thefollowing characteristics:5.4.1 A series of pat
23、terns allowing calibration of the fullfield of view as well as fractional portions of the field of viewover the range of standard magnifications. Suitable standardsallow for the pattern “pitch” to be measured,5.4.2 Pitch patterns allowing calibration in both X and Ywithout having to rotate the sampl
24、e or the raster,5.4.3 Made from materials which provide good contrast forthe various imaging modes, especially secondary electron andbackscatter electron imaging.5.4.4 Made of or coated with electrically conductive, elec-tron beam stable materials, and5.4.5 Made of materials which can be cleaned to
25、removecontamination which occurs during normal use.5.5 Under typical use some contamination of the calibrationspecimen should be expected. When cleaning becomes neces-sary always follow the manufacturers instructions. Improperhandling, especially during cleaning, may invalidate the cali-bration spec
26、imens certificate of accuracy or traceability andrequire re-certification. Care should be taken to prevent thestandard from sustaining mechanical damage which may alterthe standards structure.5.6 The facility using this practice shall have arrangementsfor the proper storage, handling, and use of the
27、 calibrationspecimen(s) which should include but is not limited to:5.6.1 Storage in a desiccating cabinet or vacuum container,5.6.2 Using finger cots, clean room gloves or tweezers whenhandling, and5.6.3 Restricting its use to calibration only, unless it can beshown that the performance of the calib
28、ration specimen will beunaffected by such use.5.7 The facility using this practice shall establish a schedulefor verification of the calibration specimen(s), where verifica-tion should include but is not limited to:5.7.1 Visual and microscopical inspection for contaminationand deterioration which ma
29、y affect performance,5.7.2 Photomicrographic comparison (and documentation)of the present state of the calibration specimen(s) to theoriginal state, and5.7.3 Validation or re-certification of calibration speci-men(s) distance intervals against other reference standards orcertified reference material
30、s.6. Procedure6.1 Mounting of the calibration specimen.6.1.1 Visually inspect the calibration specimen surface forcontamination and deterioration which may affect perfor-mance. Remove any dust or loose debris using extra care not todamage the specimen surface. One safe method is to use cleandry cann
31、ed air to remove the loose surface debris.6.1.2 Ensure good electrical contact by following the SEMand calibration specimen manufacturers directions for mount-ing. In some instances the use of a conductive cement may berequired.6.1.3 Mount the calibration specimen rigidly and securely inthe SEM spec
32、imen stage to minimize any image degradationcaused by vibration.6.2 Evacuate the SEM chamber to the desired or standardworking vacuum.6.3 Turn OFF the tilt correction and scan rotation circuits.These circuits should be calibrated independently.6.4 Set the specimen tilt to 0 such that the surface of
33、thecalibration specimen is perpendicular to the electron beam. Atechnique for checking specimen surface perpendicularity is toobserve the image focus as the specimen is translated twice thepicture width in the X or Y direction. The change of imagefocus should be minimal at a nominal magnification of
34、 1000X.6.5 Adjust the accelerating voltage, working distance, andmagnification to the desired or standard operating conditions.6.6 The instrument should be allowed to fully stabilize atthe desired operating conditions. The time required will bepre-determined by the facility using this practice.E 766
35、 98 (2008)126.7 Minimize residual magnetic hysteresis effects in thelenses by using the degauss feature, cycling lens circuitsON-OFF-ON two or three times, or follow manufacturersrecommendations.6.8 Adjust the image of the calibration specimen on theviewing CRT.6.8.1 Bring the image of the specimen
36、into sharp focus. Thesample working distance should be pre-selected to determinemagnification accuracy since different working distances mayhave different magnification errors. The specimen height (Zaxis) is then adjusted to attain focus on the viewing CRT. If theSEM has a digital working distance d
37、isplay, the desired valuemay be selected by adjusting the objective lens focus.6.8.2 Mechanically rotate the calibration specimen so themeasurement pattern(s) is parallel to the X or Y directions ofthe CRT, or both. Never use the scan rotation circuits to rotatethe image since the circuit may introd
38、uce distortions ormagnification error, or both.6.8.3 Translate the calibration specimens so the fiducialmarkings of the measurement pattern(s) span 90 % of the fulldisplay of the viewing CRT using the SEM specimen stage Xand Y controls. It is desirable to see both edges of each fiducialmarking in or
39、der to ascertain the line-center or repeated pitchdistance on the calibration specimen6.8.4 A ruler of known accuracy should be used for thesemeasurements.6.9 Viewing CRT “micrometer” marker calibration method.NOTE 1This measurement determines the micrometer marker accu-racy on the CRT for the indic
40、ated magnification (which is assumed to becorrect), and not the magnification accuracy. Often the viewing CRT is adifferent size than the record CRT and resultant micrograph. The displayedmagnification of the viewing CRT may therefore be incorrect as it wasprobably intended for the final image.6.9.1
41、 Measure the length of the “micrometer” marker (inmm 6 0.5mm) with an appropriate ruler of known accuracy.Record this value (D) and the indicated magnification. Due tothe thickness of the CRT face plate be careful that parallaxerrors in the measurement do not affect the accuracy.6.9.2 Calculate the
42、true micrometer marker size by multi-plying the indicated magnification by the displayed micrometermarker length. Calculate the percentage error by dividing thesetwo values. If the error is more than the allowable tolerance,the micrometer marker should be adjusted. This may beaccomplished by the man
43、ufacturer of the SEM or by followingthe manufacturers documented procedures.6.10 Viewing CRT Calibration Method:6.10.1 Measure with an appropriate ruler and record thepitch distance (D) between two of the fiducial markings (in mm6 0.5 mm) which are separated by the largest spacing in thefield of vie
44、w. This step must be carried out for both the X andY directions of the view CRT.6.10.1.1 If the fiducial markings are lines the measurementmust be made perpendicular to the fiducial lines and from linecenter to line center or line edge to the corresponding line edge.6.10.1.2 With some calibration sp
45、ecimens, it may be neces-sary to rotate the specimen by 90 in order to determinemagnification in both the X and Y directions. If this is the case,follow 6.10-6.10.2 before rotating the sample. Then follow6.8.2 and 6.8.3 to re-align the calibration specimen in the neworientation and repeat 6.10 and 6
46、.11.6.10.2 Calculate the magnification by using 6.12.6.11 Recording CRT calibration method.6.11.1 Photograph the field used in 6.10 with sufficientsignal to noise ratio and image contrast to allow for accuratemeasurements.6.11.2 Allow sufficient time for the photographic material tostabilize prior t
47、o measurement. This will minimize the effectsof dimensional changes in the film caused by temperature andhumidity.6.11.3 Measure and record the pitch distance (D) betweentwo of the fiducial markings (in mm 6 0.5 mm) which areseparated by the largest spacing in the photomicrograph for thebest precisi
48、on.6.11.4 It is recommended that the fiducial markings used forthe pitch measurement be at least 10 mm from the photo edgesto minimize edge distortion effects.6.11.5 If the measurement pattern consists of lines whichspan the length or width of the photomicrograph, then repeatthe measurement in 6.11.
49、3 at least three times at locationsseparated by at least 3 mm so that the average spacing may bedetermined (see Fig. 1).6.11.6 Calculate the magnification for each measurementusing 6.12. When multiple measurements have been madedetermine the mean and standard deviation for the set ofmeasurements.6.12 Calculation of Magnification:6.12.1 Calculate the true magnification (M) by dividing themeasured distance (D), usually in mm, by the accepted,certified, or 8known spacing (CS), usually in micrometers andthen multiplying by the appropriate length units conversionNOT
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