1、Designation: E 766 98 (Reapproved 2003)Standard 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, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers general procedures necessary forthe calibration of magnification of scanning electron
3、 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 The values stated in SI units are to be regarded as thestandar
4、d.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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced
5、 Documents2.1 ASTM Standards:3E 7 Terminology Relating to MetallographyE 29 Standard Practice For Using Significant Digits in TestData to Determine Conformance with SpecificationsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and Stati
6、sticsE 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 Reference Materials43. Terminology3.1 Definitions:3.1.1 For definitions of metallographic terms used in thispractic
7、e see Terminology E 7.3.1.2 The definitions related to statistical analysis of dateappearing in Practice E 77, Terminology E 456, and PracticeE 691 shall be considered as appropriate to the terms used inthis practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrationthe set of oper
8、ations which establish,under specified conditions, the relationship between magnifi-cation values indicated by the SEM and the correspondingmagnification values determined by examination of a referencematerial.3.2.2 calibration methoda technical procedure for per-forming a calibration.3.2.3 certifie
9、d 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 realization of the unit in which theproperty values are expressed, and for which each certifiedvalue is accompanied
10、 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.3.2.5 reference materiala material or substance one ormore of whose property values are sufficiently homogeneous,s
11、table, 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 reference standarda reference material, generally ofthe highest metrological quality available, from which mea-surement
12、s are derived.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 specified requirements have been
13、 met.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.Current edition approved Nov. 1, 2003. Published December 2003. Originallyapproved in 1980. Last previous edition approved
14、in 1998 E 766 98.2See Annex A1.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American Natio
15、nal Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Significance and Use4.1 Proper use of this practice can yield calibrated magni-fications with precision of 5 % o
16、r better within a magnificationrange of from 10 to 50 000X.4.2 The use of calibration specimens traceable tointernational/national standards, such as NIST-SRM 484, withthis practice will yield magnifications accurate to better than5 % over the calibrated range of operating conditions.4.3 The accurac
17、y of the calibrated magnifications, or dimen-sional measurements, will be poorer than the accuracy of thecalibration specimen used with this practice.4.4 For accuracy approaching that of the calibration speci-men this practice must be applied with the identical operatingconditions (accelerating volt
18、age, 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 standard range of magnification and operatingconditions as well as the desired accuracy for which thispractice will be applied. The standard opera
19、ting conditionsmust include those parameters which the operator can controlincluding: accelerating voltage, working distance, magnifica-tion, and imaging mode.5. Calibration Specimen5.1 The selection of calibration specimen(s) is dependent onthe magnification range and the accuracy required.5.2 The
20、use of reference standards, reference materials, orcertified reference materials traceable to international/nationalstandards (NIST, Gaithersburg, MD; NPL, Teddington, UK; orJNRLM, Tsukuba, Japan) calibration specimens is recom-mended. However, the use of internal or secondary referencematerials val
21、idated against reference standards or certifiedreference materials may be used with this practice.5.3 Where traceability to international or national standardsis not required, internal reference materials, verified as far astechnically practicable and economically feasible, are appro-priate as calib
22、ration specimens and may be used with thispractice.5.4 The most useful calibration specimens should have thefollowing characteristics:5.4.1 A series of patterns allowing calibration of the fullfield of view as well as fractional portions of the field of viewover the range of standard magnifications.
23、 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 sample or the raster,5.4.3 Made from materials which provide good contrast forthe various imaging modes, especially secondary electron andbackscatter
24、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 removecontamination which occurs during normal use.5.5 Under typical use some contamination of the calibrationspecimen should be expected. When c
25、leaning becomes neces-sary always follow the manufacturers instructions. Improperhandling, especially during cleaning, may invalidate the cali-bration specimens certificate of accuracy or traceability andrequire re-certification. Care should be taken to prevent thestandard from sustaining mechanical
26、 damage which may alterthe standards structure.5.6 The facility using this practice shall have arrangementsfor the proper storage, handling, and use of the 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
27、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 calibration specimen will beunaffected by such use.5.7 The facility using this practice shall establish a schedulefor verification of the calibration
28、specimen(s), where verifica-tion should include but is not limited to:5.7.1 Visual and microscopical inspection for contaminationand deterioration which may affect performance,5.7.2 Photomicrographic comparison (and documentation)of the present state of the calibration specimen(s) to theoriginal sta
29、te, and5.7.3 Validation or re-certification of calibration speci-men(s) distance intervals against other reference standards orcertified reference materials.6. Procedure6.1 Mounting of the calibration specimen.6.1.1 Visually inspect the calibration specimen surface forcontamination and deterioration
30、 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 canned air to remove the loose surface debris.6.1.2 Ensure good electrical contact by following the SEMand calibration specimen manufacturers directi
31、ons 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 specimen stage to minimize any image degradationcaused by vibration.6.2 Evacuate the SEM chamber to the desired or standardworking vacuum.6.3 Turn OF
32、F 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 thecalibration specimen is perpendicular to the electron beam. Atechnique for checking specimen surface perpendicularity is toobserve the image f
33、ocus 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 1000X.6.5 Adjust the accelerating voltage, working distance, andmagnification to the desired or standard operating conditions.6.6 The instrument
34、 should be allowed to fully stabilize atthe desired operating conditions. The time required will bepre-determined by the facility using this practice.6.7 Minimize residual magnetic hysteresis effects in thelenses by using the degauss feature, cycling lens circuitsON-OFF-ON two or three times, or fol
35、low manufacturersrecommendations.6.8 Adjust the image of the calibration specimen on theviewing CRT.E 766 98 (2003)26.8.1 Bring the image of the specimen into sharp focus. Thesample working distance should be pre-selected to determinemagnification accuracy since different working distances mayhave d
36、ifferent magnification errors. The specimen height (Zaxis) is then adjusted to attain focus on the viewing CRT. If theSEM has a digital working distance display, the desired valuemay be selected by adjusting the objective lens focus.6.8.2 Mechanically rotate the calibration specimen so themeasuremen
37、t 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 introduce distortions ormagnification error, or both.6.8.3 Translate the calibration specimens so the fiducialmarkings of the measurement pattern(s) spa
38、n 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 order to ascertain the line-center or repeated pitchdistance on the calibration specimen6.8.4 A ruler of known accuracy should be used for thesemeas
39、urements.6.9 Viewing CRT “micron” marker calibration method.NOTE 1This measurement determines the micron marker accuracy onthe CRT for the indicated magnification (which is assumed to be correct),and not the magnification accuracy. Often the viewing CRT is a differentsize than the record CRT and res
40、ultant micrograph. The displayedmagnification of the viewing CRT may therefore be incorrect as it wasprobably intended for the final image.6.9.1 Measure the length of the “micron” marker (in mm 60.5mm) with an appropriate ruler of known accuracy. Recordthis value (D) and the indicated magnification.
41、 Due to thethickness of the CRT face plate be careful that parallax errorsin the measurement do not affect the accuracy.6.9.2 Calculate the true micron marker size by multiplyingthe indicated magnification by the displayed micron markerlength. Calculate the percentage error by diving these twovalues
42、. If error is more than the allowable tolerance, the micronmarker should be adjusted. This may be accomplished by themanufacturer of the SEM or by following the manufacturersdocumented procedures.6.10 Viewing CRT Calibration Method:6.10.1 Measure with an appropriate ruler and record thepitch distanc
43、e (D) between two of the fiducial markings (in mm6 0.5 mm) which are separated by the largest spacing in thefield of view. 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 fiducia
44、l lines and from linecenter to line center or line edge to the corresponding line edge.6.10.1.2 With some calibration specimens, 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
45、 the sample. Then follow6.8.2 and 6.8.3 to re-align the calibration specimen in the neworientation and repeat 6.10 and 6.11.6.10.2 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 c
46、ontrast to allow for accuratemeasurements.6.11.2 Allow sufficient time for the photographic material tostabilize prior to 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
47、 fiducial markings (in mm 6 0.5 mm) which areseparated by the largest spacing in the photomicrograph for thebest precision.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 measure
48、ment pattern consists of lines whichspan the length or width of the photomicrograph, then repeatthe measurement in 6.11.3 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
49、 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 conversionfactor (CF). Conversion factors do not have to be used if thesame units in the calculation are used. For instance, if themagnified pitch distance is measured in mm, divide thatNOTE 1A 4 3
