1、Designation: F 1593 97 (Reapproved 2002)Standard 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 ye
2、ar oforiginal adoption or, in the case of revision, the 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 test method covers measuring the concentrations
3、oftrace metallic impurities 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 constituen
4、t, for example, silicon 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 req
5、uired sensitivity.This 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.2. Refere
6、nced Documents2.1 ASTM Standards:E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related Materials2E 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3E 12
7、57 Guide for Evaluating Grinding Materials Used forSurface Preparation in Spectrochemical Analysis23. 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 campai
8、gna series of analyses of similar specimensperformed 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 suit
9、able for useas a calibration/sensitivity 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 metal
10、lic impurities by this GDMS test method. 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
11、from the speci-men surface are ionized, 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
12、Miis the totalmeasured current, less 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,
13、 Mi. In all such instancesthe interfering 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 fromidentifie
14、d 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 element, M. RSFs are de
15、termined in a separate analysis1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.17 on SputterMetallization.Current edition approved Dec. 10, 2002. Published May 2003. Originallyapproved in 1995. Last previous edition
16、 approved in 1997 as F 1593 97.2Annual Book of ASTM Standards, Vol 03.05.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of a reference material performed under the same analyticalconditions,
17、 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 I(Xi) and I(Yj)in the mass spectrum, adjusted for the appropriate isotopicabundance factors (A(Xi), A(Yj) and RSFs. I(Xi) an
18、d 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 concentration ratio of atomic species Xto species Y. If species Y is taken to be the aluminum matrix(RSF(M/M) = 1.0), (X) is (wi
19、th 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 thesemiconductor industry for evaluating the purity of materials(for example, sputtering targets, evaporation sources) used inthin film
20、 metallization processes. This test method may beuseful in additional applications, not envisioned by the respon-sible technical committee, as agreed upon by the partiesconcerned.5.2 This test method is intended for use by GDMS analystsin various laboratories for unifying the protocol and parameters
21、for 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 users ofGDMS analyses as an aid to understanding the determinationmethod, and the significance and reliability of reported GDMS
22、data.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 possible.5.4 This test method may be used as a referee method forproducers and users of electronic-grade aluminum materials.6.
23、 Apparatus6.1 Glow Discharge Mass Spectrometer, with mass resolu-tion greater than 3500, and associated equipment and supplies.The GDMS must be fitted with a liquid nitrogen cooled ionsource specimen cell.6.2 Machining Apparatus, capable of preparing specimensand reference samples in the required ge
24、ometry and withsmooth surfaces.6.3 Electropolishing Apparatus, capable of removing thecontaminants from the surfaces 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 Refer
25、ence Sample.7.4.1 To the extent available, Aluminum reference materialsshall be used to produce the GDMS relative 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 factor
26、s forthe various elements being determined.7.4.3 Reference materials should be homogeneous and freeof cracks or porosity.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 th
27、ebackground contribution in analyses.7.4.5 The concentration of each analyte for relative sensi-tivity factor determination 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
28、analysis precision, it is necessarythat specimens of reference and test material present the samesize and configuration (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 Ref
29、erence Standards and TestSpecimens8.1 The surface of the parent material must not be includedin the specimen.8.2 The 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 or
30、der to obtain a representative bulk composition ina reasonable analysis time, surface cleaning must remove allcontaminants without altering the composition of the specimensurface.8.2.2 To minimize the possibility of contamination, cleaneach specimen separately immediately prior to mounting in theglo
31、w discharge ion source.8.2.3 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) across the cell, with th
32、e 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 byTABLE 1 Suite of Impurity Elements to Be AnalyzedANOTEEstablish RSF
33、s for the following suite 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, a
34、s agreed upon between all parties concerned with the analyses.F 1593 97 (2002)2volume). Etch for several minutes, until smooth, 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
35、remove water from the specimen surface, and drythe specimen in the laboratory environment.8.3 Immediately mount and insert 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-contactin
36、g gage when mount-ing specimens in the analysis cell specimen holder to ensurethe proper sample configuration in the glow 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 th
37、e surface. Pre-analysis sputteringconditions are limited by the need to maintain sample integrity.Pre-analysis sputtering 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 sourcecha
38、mber should be less than 1 3 106Torr before operation.The background pressure in the mass analyzer should be lessthan 5 3 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
39、measurements.9.4 The GDMS instrument must be adjusted to the appro-priate mass peak shape and mass resolving power for therequired 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 th
40、e others should bedetermined at least weekly.9.5.1 If both Faraday cup collector for ion current measure-ment and ion counting 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 equivalen
41、t procedures.9.5.1.1 Using a specimen of tantalum, measure the ioncurrent from the major isotope (181Ta) using the ion currentFaraday 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 sys
42、tem deadtimes. The counting loss should be 1 % or less.9.5.1.2 The ion counting efficiency is calculated by multi-plying 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 Appl
43、y the ICE as a correction to all ion currentmeasurements from the ion counting detector obtained inanalyses by dividing the 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
44、a whole for the required analyses.10.2 A recommended procedure is the measurement of therelative ion currents of selected 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
45、 control (SPC) chartformat to demonstrate that the analysis process is in statisticalcontrol. The equipment is suitable for 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
46、mean of previously determined values ofthe relative ion currents.11. Standardization11.1 The GDMS instrument should be standardized usingNational Institute of Standards Technology (NIST) traceablereference materials, preferably aluminum, to the extent suchreference samples are available.11.2 Relativ
47、e sensitivity factor (RSF) values should, in thebest case, be determined from the ion beam ratio measurementsof four randomly 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 s
48、pecimens 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,
49、themeasurement of elements tabulated in Table 1 and the isotopestabulated in Table 2.12.1.2 Instrumental parameters selected for isotope mea-surements must be appropriate for the analysis requirements:12.1.2.1 Ion current integration times to achieve desiredprecision and detection limits; and,12.1.2.2 Mass ranges about the analyte mass peak overwhich measurements are acquired to clarify mass interferences.TABLE 2 Isotope SelectionANOTEUse the following isotopes for establishing RSF values and forperforming analyses of test specimens.109Ag63Cu/65Cu121Sb75As56Fe28Si1
