ASTM E1127-2008(2015) Standard Guide for Depth Profiling in Auger Electron Spectroscopy《采用俄歇电子能谱学进行深度剖面的标准指南》.pdf

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1、Designation: E1127 08 (Reapproved 2015)Standard Guide forDepth Profiling in Auger Electron Spectroscopy1This standard is issued under the fixed designation E1127; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev

2、ision. 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 guide covers procedures used for depth profiling inAuger electron spectroscopy.1.2 Guidelines are given for depth profili

3、ng by the follow-ing:SectionIon Sputtering 6Angle Lapping and Cross-Sectioning 7Mechanical Cratering 8Mesh Replica Method 9Nondestructive Depth Profiling 101.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard do

4、es not purport to address all of thesafety problems, 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 Sta

5、ndards:2E673 Terminology Relating to SurfaceAnalysis (Withdrawn2012)3E684 Practice for Approximate Determination of CurrentDensity of Large-Diameter Ion Beams for Sputter DepthProfiling of Solid Surfaces (Withdrawn 2012)3E827 Practice for Identifying Elements by the Peaks inAuger Electron Spectrosco

6、pyE996 Practice for Reporting Data in Auger Electron Spec-troscopy and X-ray Photoelectron SpectroscopyE1078 Guide for Specimen Preparation and Mounting inSurface AnalysisE1577 Guide for Reporting of Ion Beam Parameters Used inSurface AnalysisE1634 Guide for Performing Sputter Crater Depth Measure-m

7、entsE1636 Practice for Analytically Describing Depth-Profileand Linescan-Profile Data by an Extended Logistic Func-tionE1829 Guide for Handling Specimens Prior to SurfaceAnalysis2.2 ISO Standard:4ISO/TR 22335: 2007 Surface Chemical AnalysisDepthProfilingMeasurement of Sputtering Rate: Mesh-Replica M

8、ethod Using a Mechanical Stylus Profilometer3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology E673.4. Summary of Guide4.1 In ion sputtering, the surface layers are removed by ionbombardment in conjunction with Auger analysis.4.2 In angle lapping, th

9、e surface is lapped or polished at asmall angle to improve the depth resolution as compared to across section.4.3 In mechanical cratering, a spherical or cylindrical crateris created in the surface using a rotating ball or wheel. Thesloping sides of the crater are used to improve the depthresolution

10、 as in angle lapping.4.4 In nondestructive techniques, different methods of vary-ing the electron information depth are involved.5. Significance and Use5.1 Auger electron spectroscopy yields information con-cerning the chemical and physical state of a solid surface in thenear surface region. Nondest

11、ructive depth profiling is limitedto this near surface region. Techniques for measuring the craterdepths and film thicknesses are given in (1).51This guide is under the jurisdiction of ASTM Committee E42 on SurfaceAnalysisand is the direct responsibility of Subcommittee E42.03 on Auger ElectronSpect

12、roscopy and X-Ray Photoelectron Spectroscopy.Current edition approved June 1, 2015. Published June 2015. Originallyapproved in 1986. Last previous edition approved in 2008 as E1127 08. DOI:10.1520/E1127-08R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom

13、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from International Organization for Standardization (ISO)

14、, 1, ch. dela Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.5The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 Ion

15、sputtering is primarily used for depths of less thanthe order of 1 m.5.3 Angle lapping or mechanical cratering is primarily usedfor depths greater than the order of 1 m.5.4 The choice of depth profiling methods for investigatingan interface depends on surface roughness, interfaceroughness, and film

16、thickness (2).5.5 The depth profile interface widths can be measuredusing a logistic function which is described in Practice E1636.6. Ion Sputtering6.1 The specimen should be handled in accordance withGuides E1078 and E1829. First introduce the specimen into avacuum chamber equipped with an Auger an

17、alyzer and an ionsputtering gun. Align the ion beam using a sputtering target ora Faraday cup, paying careful attention to the relative spot sizeof the electron beam, ion beam, and Faraday cup and theirrespective orientations to ensure accurate convergence of thetwo beams at the specimen surface.6.1

18、.1 Place the specimen in front of the Auger analyzer anddirect the ion gun towards the analysis area. If the ion beam isnot normal to the specimen surface then possible shadowing ofthe analysis area from the ion beam, due to surface roughness,must be considered. The ion beam conditions should berepo

19、rted in accordance with Guide E1577.6.2 Choose the elements to be investigated from previousexperience or from an initial Auger electron spectrum or anenergy-dispersive X-ray spectrum since the latter spectrum canreveal additional elements present at depths greater than thosethat contribute to the A

20、uger electron spectrum (3). Select aspecific transition for each element. During the depth profiling,record the peak-to-peak heights for Auger derivative data, orpeak heights or peak areas for N(E) data. The data may begathered during continuous sputtering or between timed sputtersegments. Results m

21、ay vary between the two techniques.6.2.1 One source of their difference is due to the presence ofion-induced electrons during continuous sputter depthprofiling, especially at low-electron kinetic energies, that canbecome comparable in intensity to the electrons induced by theprobing incident electro

22、n beam. Unless one or the other of theexcitation beams is modulated and detected synchronouslythese two types of emitted electrons are difficult to distinguish.These ion-induced electrons usually form a featureless back-ground that rises steeply as their kinetic energy decreases, butsometimes ion-in

23、duced Auger peaks might be present whoselineshape may be different from those produced by the electronbeam (4). As a result, care must be taken during continuoussputtering to ensure reliable results. Another source of differ-ence is due to the buildup of adsorbed species during the dataacquisition t

24、ime in the discontinuous sputter depth profilemode (5). If portions of the ion-eroded surface expose veryreactive phases, then Auger peaks due to adsorbed species, forexample, oxygen or carbon, or both, will appear in the spectraand mask the actual depth distribution.6.2.2 It is advisable when analy

25、zing an unknown specimento periodically examine survey scans to detect any newelements that were not present in the initial survey scan and todetermine if any of the Auger peaks have been displacedoutside of their analysis windows (6).6.3 Crater-edge profiling of the sputter-formed crater byusing Au

26、ger line scans is a technique similar to the analysis ofthe mechanically formed craters in Section 8 (7). Forming thecrater by sputtering may introduce the additional complicationsof ion-induced damage and asymmetric crater dimensions.6.4 If specimen rotation is used to reduce ion-inducedroughness,

27、then the rotational speed, rotation axis runoutrelative to ion beam sputtered area or wobble and dataacquisition rate should be reported (8, 9).6.5 Identify the elements in the survey scans using PracticeE827.6.6 The Auger data and the sputtering conditions should bereported as described in Practice

28、 E996.6.7 There is extensive information available in the literatureon the effects of ion bombardment on solid surfaces (10-15).6.8 Special care must be exercised whenever specimentemperature changes are present because effects due to surfacediffusion, surface segregation or diffusion limited bulk p

29、ro-cesses such as point defect migration can occur and dramati-cally alter the specimen composition, even over depths largerthan the ion beam penetration depth which is typically a fewnanometers (16, 17). The concept of preferential sputtering inmultielement, single-phase specimens has altered signi

30、ficantlyso that chemical effects such as surface segregation areconsidered to be at least as important as physical effects suchas mass differences in the evolution of the near surfacecomposition during sputter depth profiling (18-21). Since theprobing depths in Auger electron spectroscopy are usuall

31、ysmaller than the ion-penetration depth these effects are veryimportant in any interpretation of Auger signal intensity interms of composition during ion-beam profiling. Computermodelling of these and other ion-induced phenomena has beenextensively studied and has provided new insights into thisfiel

32、d (22, 23).6.8.1 It should be determined for each specimen if compo-sitional changes or other sputter effects are likely to occur. Itmay be possible to minimize these effects in some instances byadjusting the sputtering parameters.6.9 Ion guns used in Auger analysis are normally self-contained units

33、 capable of producing a focused beam of ions.The specimen is not used as an anode for the gun. Many ionguns are able to raster the ion beam. A rastered ion beam willproduce a more uniform ion current distribution on thespecimen surface in the region of analysis.6.10 If the ion gun is differentially

34、pumped, the vacuumpumps may be left on during sputtering, removing most of thesputtered gases. If not, then the chamber must be back filledwith gas and provisions for removing the sputtered active gasesmust be considered. Titanium sublimation is effective inremoving these gases.6.11 Noble gas ions a

35、re normally used in sputtering and themost commonly used gas is argon. Xenon is occasionally usedE1127 08 (2015)2with high beam energies when rapid sputtering is needed.Active gases such as oxygen and metal ions are used in specialcircumstances.6.11.1 Ion energies commonly used for depth profilingus

36、ing noble gases are in the range from 1 to 5 keV where lowerion energies are usually preferred for improved depth resolu-tion. Higher ion energies usually can be obtained with higherion currents and less preferential sputtering.6.11.2 Ion beam current density can be measured by aFaraday cup or by fo

37、llowing Practice E684.6.11.3 The sputter rate is needed to calibrate the depth scale(24, 25, Guide E1634) when depth profiling using ion sputter-ing. Several reference standards are available for this purpose.One reference material consists of 30 and 100-nm thicktantalum pentoxide films (26).6Anothe

38、r reference material isan alternating nickel and chromium thin film structure; eachlayer is nominally 50-nm thick.77. Angle Lapping and Cross-Sectioning7.1 In cross-sectioning, polish the specimen perpendicularto the interface, while in angle lapping, polish the specimen atan angle to increase the d

39、epth resolution as shown in Fig. 1(27). Polishing usually includes the use of silicon carbidepapers, diamond paste, and alumina. Use progressively finerpolishing particles to obtain the desired surface finish. Possiblelimitations of the techniques include smearing of materialacross the interface, su

40、rface roughness, and the electron probediameter limiting the spatial resolution.7.2 In angle lapping mount the specimen on a flat gageblock and measure the angle with a collimator. The accuracydepends on the flatness of the specimen. In practice an angle of0.1 can be accurately measured.7.3 The dept

41、h, d, is given by the following equation:d 5 Ytan (1)where (in Fig. 1) is the lapped angle and Y is the distancefrom the edge.7.4 The depth resolution, d, is given by the followingequation: d 5 Ytan (2)where Y includes the electron beam diameter and uncer-tainties in position that may be due to erro

42、rs in specimen orelectron beam positioning.7.5 Auger analysis can include line scans and point analysisalong the lapped surface. Perform the analysis by eithermoving the specimen using micrometer adjustments or byelectronically moving the electron beam.7.6 Ion sputtering (Section 6) is often used in

43、 conjunctionwith angle lapping to remove contaminants and to investigateinterfaces beneath the lapped surfaces.7.7 Consideration should be given if specimen mountingmethods, for example, plastic embedding media, are usedwhich may employ high vapor pressure materials. Out-gassingof the media as well

44、as trapped gases between the media andthe specimen may require complete removal of the mountingmaterials prior to analysis.8. Mechanical Cratering8.1 Ball Cratering:8.1.1 First mount the specimen in a device where a rotatingsteel ball can be placed against its surface. Commercialapparatus is availab

45、le that uses a rotating shaft with a notch thatholds the ball and spins it. The rotational speed and the forceagainst the specimen can be adjusted (28).8.1.2 Coat the ball with an abrasive material to improve thecratering rate. In practice diamond paste is used with a particlesize of 0.1 to 1 m. The

46、 larger particle sizes will give the mostrapid cratering rates and the finer particle sizes will give thesmoothest crater wall surface. The coarser pastes can be usedfirst to form the crater and the fine pastes can be used to smooththe crater wall. As with cross-sectioning and angle lapping,consider

47、ation should be given to the possibility of smearingmaterial across the cratered surface.8.1.3 The geometry of the crater is shown in Fig. 2. Thedepth of the crater, d, is given by the following equation:d 5 D2/8R (3)6Available from the National Physical Laboratory (NPL), Hampton Road,Teddington, Mi

48、ddlesex, TW11 0LW, UK, http:/www.npl.co.uk. Listed as CertifiedReference Material NPL No. S7B83, BCR No. 261.7Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov. Listedas NIST Standard Reference Material 213

49、5.NOTE 1In practice, the angle is much smaller than shown, being ofthe order of 1.FIG. 1 Cross Section of Angle-Lapped SpecimenFIG. 2 Cross Section of Specimen After Ball-Cratering Using aSphere of Radius, R, to a depth, dE1127 08 (2015)3where:D = the diameter of the crater,R = the radius of the ball, andR =D/2.8.1.4 TheAuger analysis is the same as described in 7.5 and7.6.8.1.5 The depth at any point in the analysis, Z, is given bythe following equation (2):Z 5 R22 x21Dx 2 D2/4!1/22 R22 D2/4!1/2(4)where x is the lateral distance from the crater edge. Thedep