1、Designation: F 1593 08Standard Test Method forTrace Metallic Impurities in Electronic Grade Aluminum byHigh Mass-Resolution Glow-Discharge Mass Spectrometer1This standard is issued under the fixed designation F 1593; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, 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.1. Scope1.1 This test method covers measuring the concentrations oftrace metallic im
3、purities in high purity aluminum.1.2 This test method pertains to analysis by magnetic-sectorglow discharge mass spectrometer (GDMS).1.3 The aluminum matrix must be 99.9 weight % (3N-grade) pure, or purer, with respect to metallic impurities. Theremust be no major alloy constituent, for example, sil
4、icon orcopper, greater than 1000 weight ppm in concentration.1.4 This test method does not include all the informationneeded to complete GDMS analyses. Sophisticated computer-controlled laboratory equipment skillfully used by an experi-enced operator is required to achieve the required sensitivity.T
5、his test method does cover the particular factors (for example,specimen preparation, setting of relative sensitivity factors,determination of sensitivity limits, etc.) known by the respon-sible technical committee to affect the reliability of high purityaluminum analyses.1.5 This standard does not p
6、urport 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 Documents2.1 ASTM Standards:2
7、E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1257 Guide for Evaluating Grinding Mat
8、erials Used forSurface Preparation in Spectrochemical Analysis3. Terminology3.1 Terminology in this test method is consistent withTerminology E 135. Required terminology specific to this testmethod and not covered in Terminology E 135 is indicatedbelow.3.2 campaigna series of analyses of similar spe
9、cimensperformed in the same manner in one working session, usingone GDMS setup. As a practical matter, cleaning of the ionsource specimen cell is often the boundary event separatingone analysis campaign from the next.3.3 reference sample material accepted as suitable for useas a calibration/sensitiv
10、ity reference standard by all partiesconcerned with the analyses.3.4 specimena suitably sized piece cut from a reference ortest sample, prepared for installation in the GDMS ion source,and analyzed.3.5 test sample material (aluminum) to be analyzed fortrace metallic impurities by this GDMS test meth
11、od. Generallythe test sample is extracted from a larger batch (lot, casting) ofproduct and is intended to be representative of the batch.4. Summary of the Test Method4.1 A specimen is mounted as the cathode in a plasmadischarge cell. Atoms subsequently sputtered from the speci-men surface are ionize
12、d, and then focused as an ion beamthrough a double-focusing magnetic-sector mass separationapparatus. The mass spectrum, that is, the ion current, iscollected as magnetic field, or acceleration voltage is scanned,or both.4.2 The ion current of an isotope at mass Miis the totalmeasured current, less
13、contributions from all other interferingsources. Portions of the measured current may originate fromthe ion detector alone (detector noise). Portions may be due toincompletely mass resolved ions of an isotope or molecule withmass close to, but not identical with, Mi. In all such instancesthe interfe
14、ring contributions must be estimated and subtractedfrom the measured signal.4.2.1 If the source of interfering contributions to the mea-sured ion current at Micannot be determined unambiguously,the measured current less the interfering contributions from1This test method is under the jurisdiction of
15、 ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.17 on SputterMetallization.Current edition approved June 15, 2008. Published July 2008. Originallyapproved in 1995. Last previous edition approved in 2002 as F 1593 97(2002).2For referenced ASTM standards, visit t
16、he 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
17、 United States.identified sources constitutes an upper bound of the detectionlimit for the current due to the isotope.4.3 The composition of the test specimen is calculated fromthe mass spectrum by applying a relative sensitivity factor(RSF(X/M) for each contaminant element, X, compared to thematrix
18、 element, M. RSFs are determined in a separate analysisof a reference material performed under the same analyticalconditions, source configuration, and operating protocol as forthe test specimen.4.4 The relative concentrations of elements X and Y arecalculated from the relative isotopic ion currents
19、 I(Xi) and I(Yj)in the mass spectrum, adjusted for the appropriate isotopicabundance factors (A(Xi), A(Yj) and RSFs. I(Xi) and I(Yj) referto the measured ion current from isotopes Xiand Yj, respec-tively, of atomic species X and Y.X!/Y!5RSFX/M!/RSFY/M!3AYj!/AXi!3IXi!/IYi! (1)where (X)/(Y) is the con
20、centration ratio of atomic species Xto species Y. If species Y is taken to be the aluminum matrix(RSF(M/M) = 1.0), (X) is (with only very small error for puremetal matrices) the absolute impurity concentration of X.5. Significance and Use5.1 This test method is intended for application in thesemicon
21、ductor industry for evaluating the purity of materials(for example, sputtering targets, evaporation sources) used inthin film metallization processes. This test method may beuseful in additional applications, not envisioned by the respon-sible technical committee, as agreed upon by the partiesconcer
22、ned.5.2 This test method is intended for use by GDMS analystsin various laboratories for unifying the protocol and parametersfor determining trace impurities in pure aluminum. The objec-tive is to improve laboratory to laboratory agreement ofanalysis data. This test method is also directed to the us
23、ers ofGDMS analyses as an aid to understanding the determinationmethod, and the significance and reliability of reported GDMSdata.5.3 For most metallic species the detection limit for routineanalysis is on the order of 0.01 weight ppm. With specialprecautions detection limits to sub-ppb levels are p
24、ossible.5.4 This test method may be used as a referee method forproducers and users of electronic-grade aluminum materials.6. Apparatus6.1 Glow Discharge Mass Spectrometer, with mass resolu-tion greater than 3500, and associated equipment and supplies.The GDMS must be fitted with an ion source speci
25、men cell thatis cooled by liquid nitrogen, Peltier cooled, or cooled by anequivalent method.6.2 Machining Apparatus, capable of preparing specimensand reference samples in the required geometry and withsmooth surfaces.6.3 Electropolishing Apparatus, capable of removing thecontaminants from the surfa
26、ces of specimens.7. Reagents and Materials7.1 Reagent and High Purity Grade Reagents, as required(MeOH, HNO3, HCl).7.2 Demineralized Water.7.3 Tantalum Reference Sample.7.4 Aluminum Reference Sample.7.4.1 To the extent available,Aluminum reference materialsshall be used to produce the GDMS relative
27、sensitivity factorsfor the various elements being determined (see Table 1).7.4.2 As necessary, non-aluminum reference materials maybe used to produce the GDMS relative sensitivity factors forthe various elements being determined.7.4.3 Reference materials should be homogeneous and freeof cracks or po
28、rosity.7.4.4 At least two reference materials are required to estab-lish the relative sensitivity factors, including one nominally99.9999 % pure (6N-grade) aluminum metal to establish thebackground contribution in analyses.7.4.5 The concentration of each analyte for relative sensi-tivity factor dete
29、rmination should be a factor of 100 greaterthan the detection limit determined using a nominally99.9999 % pure (6N-grade) aluminum specimen, but less than100 ppmw.7.4.6 To meet expected analysis precision, it is necessarythat specimens of reference and test material present the samesize and configur
30、ation (shape and exposed length) in the glowdischarge ion source, with a tolerance of 0.2 mm in diameterand 0.5 mm in the distance of specimen to cell ion exit slit.8. Preparation of Reference Standards and TestSpecimens8.1 The surface of the parent material must not be includedin the specimen.8.2 T
31、he machined surface of the specimen must be cleanedby electropolishing or etching immediately prior to mountingthe specimen and inserting it into the glow discharge ionsource.8.2.1 In order to obtain a representative bulk composition ina reasonable analysis time, surface cleaning must remove allcont
32、aminants without altering the composition of the specimensurface.8.2.2 To minimize the possibility of contamination, cleaneach specimen separately immediately prior to mounting in theglow discharge ion source.TABLE 1 Suite of Impurity Elements to Be AnalyzedANOTEEstablish RSFs for the following suit
33、e of elements.silver arsenic gold boron beryllium calcium cerium chromium cesium copper ironpotassium lithium magnesium manganese sodium nickel phosphorus antimony silicon tin thoriumtitanium uranium vanadium zinc zirconiumAAdditional species may be determined and reported, as agreed upon between al
34、l parties concerned with the analyses.F 1593 0828.2.3 Prepare and use electropolishing or etching solutionsin a clean container insoluble in the contained solution.8.2.4 Electropolishing perform electropolishing in a so-lution of methanol and HNO3mixed in the ratio 7:5 by volume.Apply 515 volts (dc)
35、 across the cell, with the specimen asanode. Electropolish for up to 4 min, as sufficient to exposesmooth, clean metal over the entire polished surface.8.2.5 Etchingperform etching by immersing the specimenin aqua regia (HNO3and HF, mixed in the ratio 3:1 byvolume). Etch for several minutes, until s
36、mooth, clean metal isexposed over the entire surface.8.2.6 Immediately after cleaning, wash the specimen withseveral rinses of high purity methanol or other high purityreagent to remove water from the specimen surface, and drythe specimen in the laboratory environment.8.3 Immediately mount and inser
37、t the specimen into theglow discharge ion source, minimizing exposure of thecleaned, rinsed specimen surface to the laboratory environ-ment.8.3.1 As necessary, use a non-contacting gage when mount-ing specimens in the analysis cell specimen holder to ensurethe proper sample configuration in the glow
38、 discharge cell (see7.4.6).8.4 Sputter etch the specimen surface in the glow dischargeplasma for a period of time before data acquisition (see 12.3)to ensure the cleanliness of the surface. Pre-analysis sputteringconditions are limited by the need to maintain sample integrity.Pre-analysis sputtering
39、 at twice the power used for the analysisshould be adequate for sputter etch cleaning.9. Preparation of the GDMS Apparatus9.1 The ultimate background pressure in the ion sourcechamber should be less than 1 3 106Torr before operation.The background pressure in the mass analyzer should be lessthan 5 3
40、 107Torr during operation.9.2 The glow discharge ion source must be cooled to nearliquid nitrogen temperature.9.3 The GDMS instrument must be accurately mass cali-brated prior to measurements.9.4 The GDMS instrument must be adjusted to the appro-priate mass peak shape and mass resolving power for th
41、erequired analysis.9.5 If the instrument uses different ion collectors to measureion currents during the same analysis, the measurement effi-ciency of each detector relative to the others should bedetermined at least weekly.9.5.1 If both Faraday cup collector for ion current measure-ment and ion cou
42、nting detectors are used during the sameanalysis, the ion counting efficiency (ICE) must be determinedprior to each campaign of specimen analyses using the follow-ing or equivalent procedures.9.5.1.1 Using a specimen of tantalum, measure the ioncurrent from the major isotope (181Ta) using the ion cu
43、rrentFaraday cup detector, and measure the ion current from theminor isotope (180Ta) using the ion counting detector, with careto avoid ion counting losses due to ion counting system deadtimes. The counting loss should be 1 % or less.9.5.1.2 The ion counting efficiency is calculated by multi-plying
44、the ratio of the180Ta ion current to the181Ta ion currentby the181Ta/180Ta isotopic ratio. The result of this calculationis the ion counting detector efficiency (ICE).9.5.1.3 Apply the ICE as a correction to all ion currentmeasurements from the ion counting detector obtained inanalyses by dividing t
45、he ion current by the ICE factor.10. Instrument Quality Control10.1 A well-characterized specimen must be run on aregular basis to demonstrate the capability of the GDMSsystem as a whole for the required analyses.10.2 A recommended procedure is the measurement of therelative ion currents of selected
46、 analytes and the matrixelement in aluminum or tantalum reference samples.10.3 Plot validation analysis data from at least five elementswith historic values in statistical process control (SPC) chartformat to demonstrate that the analysis process is in statisticalcontrol. The equipment is suitable f
47、or use if the analysis datagroup is within the 3-sigma control limits and shows nonon-random trends.10.4 Upper and lower control limits for SPC must be withinat least 20 % of the mean of previously determined values ofthe relative ion currents.11. Standardization11.1 The GDMS instrument should be st
48、andardized usingNational Institute of Standards Technology (NIST) traceablereference materials, preferably aluminum, to the extent suchreference samples are available.11.2 Relative sensitivity factor (RSF) values should, in thebest case, be determined from the ion beam ratio measurementsof four rand
49、omly selected specimens from each standardrequired, with four independent measurements of each pin.11.3 RSF values must be determined for the suite ofimpurity elements for which specimens are to be analyzed (seeTable 1) using the selected isotopes (see Table 2) for measure-ment and RSF calculation.12. Procedure12.1 Establish a suitable data acquisition protocol (DAP)appropriate for the GDMS instrument used for the analysis.12.1.1 The DAP must include, but is not limited to, themeasurement of elements tabulated in Table 1 and the isotopestabulated in Table 2.12.1.
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