ASTM E1127-2008 Standard Guide for Depth Profiling in Auger Electron Spectroscopy《俄歇电子能谱学中的深度压形的标准指南》.pdf

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1、Designation: E 1127 08Standard Guide forDepth Profiling in Auger Electron Spectroscopy1This standard is issued under the fixed designation E 1127; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number

2、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 profiling by the follow

3、-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 does not purport t

4、o 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 Standards:2E 673 Te

5、rminology Relating to Surface AnalysisE 684 Practice for Approximate Determination of CurrentDensity of Large-Diameter Ion Beams for Sputter DepthProfiling of Solid SurfacesE 827 Practice for Identifying Elements by the Peaks inAuger Electron SpectroscopyE 996 Practice for Reporting Data in Auger El

6、ectron Spec-troscopy and X-ray Photoelectron SpectroscopyE 1078 Guide for Specimen Preparation and Mounting inSurface AnalysisE 1577 Guide for Reporting of Ion Beam Parameters Usedin Surface AnalysisE 1634 Guide for Performing Sputter Crater Depth Mea-surementsE 1636 Practice for Analytically Descri

7、bing Sputter-Depth-Profile Interface Data by an Extended Logistic FunctionE 1829 Guide for Handling Specimens Prior to SurfaceAnalysis2.2 ISO Standards:3ISO/TR 22335: 2007 Surface Chemical AnalysisDepthProfilingMeasurement of Sputtering Rate: Mesh-Replica Method Using a Mechanical Stylus Profilomete

8、r3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology E 673.4. Summary of Guide4.1 In ion sputtering, the surface layers are removed by ionbombardment in conjunction with Auger analysis.4.2 In angle lapping, the surface is lapped or polished at asmall

9、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 as in angle lapping.4.4 In nondestructive

10、 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. Nondestructive depth profiling is limitedto this

11、near surface region. Techniques for measuring the craterdepths and film thicknesses are given in (1).45.2 Ion sputtering is primarily used for depths of less thanthe order of 1 m.1This guide is under the jurisdiction of ASTM Committee E42 on SurfaceAnalysis and is the direct responsibility of Subcom

12、mittee E42.03 on Auger ElectronSpectroscopy and X-Ray Photoelectron Spectroscopy.Current edition approved Oct. 1, 2008. Published November 2008. Originallyapproved in 1986. Last previous edition approved in 2003 as E 1127 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon

13、tact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Swit

14、zerland, http:/www.iso.ch.4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 Angle lapping or mechanical cratering is primarily usedfor de

15、pths greater than the order of 1 m.5.4 The choice of depth profiling methods for investigatingan interface depends on surface roughness, interface rough-ness, and film thickness (2).5.5 The depth profile interface widths can be measuredusing a logistic function which is described in Practice E 1636.

16、6. Ion Sputtering6.1 The specimen should be handled in accordance withGuides E 1078 and E 1829. First introduce the specimen into avacuum chamber equipped with an Auger analyzer and an ionsputtering gun. Align the ion beam using a sputtering target ora Faraday cup, paying careful attention to the re

17、lative spot sizeof the electron beam, ion beam, and Faraday cup and theirrespective orientations to ensure accurate convergence of thetwo beams at the specimen surface.6.1.1 Place the specimen in front of the Auger analyzer anddirect the ion gun towards the analysis area. If the ion beam isnot norma

18、l 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 bereported in accordance with Guide E 1577.6.2 Choose the elements to be investigated from previousexperience or from an initial Auger

19、electron spectrum or anenergy-dispersive X-ray spectrum since the latter spectrum canreveal additional elements present at depths greater than thosethat contribute to the Auger electron spectrum (3). Select aspecific transition for each element. During the depth profiling,record the peak-to-peak hei

20、ghts 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 may vary between the two techniques.6.2.1 One source of their difference is due to the presence ofion-induced electrons during co

21、ntinuous sputter depth profil-ing, especially at low-electron kinetic energies, that can be-come comparable in intensity to the electrons induced by theprobing incident electron beam. Unless one or the other of theexcitation beams is modulated and detected synchronouslythese two types of emitted ele

22、ctrons are difficult to distinguish.These ion-induced electrons usually form a featureless back-ground that rises steeply as their kinetic energy decreases, butsometimes ion-induced Auger peaks might be present whoselineshape may be different from those produced by the electronbeam (4). As a result,

23、 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 time in the discontinuous sputter depth profilemode (5). If portions of the ion-eroded surface expose veryreactive phases, th

24、en 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 analyzing an unknown specimento periodically examine survey scans to detect any newelements that were not present in the initial

25、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 Auger line scans is a technique similar to the analysis ofthe mechanically formed craters in Section 8 (7). Forming thecrater

26、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, then the rotational speed, rotation axis runoutrelative to ion beam sputtered area or wobble and dataacquisition rate should

27、 be reported (8, 9).6.5 Identify the elements in the survey scans using PracticeE 827.6.6 The Auger data and the sputtering conditions should bereported as described in Practice E 996.6.7 There is extensive information available in the literatureon the effects of ion bombardment on solid surfaces (1

28、0-15).6.8 Special care must be exercised whenever specimentemperature changes are present because effects due to surfacediffusion, surface segregation or diffusion limited bulk pro-cesses such as point defect migration can occur and dramati-cally alter the specimen composition, even over depths larg

29、erthan the ion beam penetration depth which is typically a fewnanometers (16, 17). The concept of preferential sputtering inmultielement, single-phase specimens has altered significantlyso that chemical effects such as surface segregation areconsidered to be at least as important as physical effects

30、 suchas mass differences in the evolution of the near surfacecomposition during sputter depth profiling (18-21). Since theprobing depths in Auger electron spectroscopy are usuallysmaller than the ion-penetration depth these effects are veryimportant in any interpretation of Auger signal intensity in

31、terms of composition during ion-beam profiling. Computermodelling of these and other ion-induced phenomena has beenextensively studied and has provided new insights into thisfield (22, 23).6.8.1 It should be determined for each specimen if compo-sitional changes or other sputter effects are likely t

32、o 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 capable of producing a focused beam of ions.The specimen is not used as an anode for the gun. Many ionguns are able to ra

33、ster 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 pumped, the vacuumpumps may be left on during sputtering, removing most of thesputtered gases. If not, then the chamber mu

34、st 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 are normally used in sputtering and themost commonly used gas is argon. Xenon is occasionally usedwith high beam energies w

35、hen 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 profilingusing noble gases are in the range from 1 to 5 keV where lowerion energies are usually preferred for improved depth resolu-tion. Higher ion

36、energies usually can be obtained with higherion currents and less preferential sputtering.E11270826.11.2 Ion beam current density can be measured by aFaraday cup or by following Practice E 684.6.11.3 The sputter rate is needed to calibrate the depth scale(24, 25, Guide E 1634) when depth profiling u

37、sing ion sput-tering. Several reference standards are available for this pur-pose. One reference material consists of 30 and 100-nm thicktantalum pentoxide films (26).5Another reference material isan alternating nickel and chromium thin film structure; eachlayer is nominally 50-nm thick.67. Angle La

38、pping 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 depth resolution as shown in Fig. 1(27). Polishing usually includes the use of silicon carbidepapers, diamond paste, and alumin

39、a. Use progressively finerpolishing particles to obtain the desired surface finish. Possiblelimitations of the techniques include smearing of materialacross the interface, surface roughness, and the electron probediameter limiting the spatial resolution.7.2 In angle lapping mount the specimen on a f

40、lat 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 depth, d, is given by the following equation:d 5 Y tan u (1)where (in Fig. 1) u is the lapped angle and Y is the distancefrom the

41、edge.7.4 The depth resolution, Dd, is given by the followingequation:D d 5DY tan u (2)where DY includes the electron beam diameter and uncer-tainties in position that may be due to errors in specimen orelectron beam positioning.7.5 Auger analysis can include line scans and point analysisalong the la

42、pped 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 conjunctionwith angle lapping to remove contaminants and to investigateinterfaces beneath the lapped surfaces.7.7

43、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 as trapped gases between the media andthe specimen may require complete removal of the mountingmaterials prior to a

44、nalysis.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 available that uses a rotating shaft with a notch thatholds the ball and spins it. The rotational speed and the forceagain

45、st 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 larger particle sizes will give the mostrapid cratering rates and the finer particle sizes will give thesmoothest

46、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,consideration should be given to the possibility of smearingmaterial across the cratered surface.8.1.3 The geometry of the

47、crater is shown in Fig. 2. Thedepth of the crater, d, is given by the following equation:d 5 D2/8R (3)where: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 by

48、the following equation (2):Z 5 R22 x21 Dx 2 D2/4!1/22 R22 D2/4!1/2(4)where x is the lateral distance from the crater edge. Thedepth may also be given by the approximation as follows:5Available from the National Physical Laboratory, Hampton Road, Teddington,Middlesex, TW11 0LW, UK, http:/www.npl.co.u

49、k. Listed as Certified ReferenceMaterial NPL No. S7B83, BCR No. 261.6Available 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 2135.NOTE 1In practice, the angle u 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, dE1127083Z 5 xD 2 x!/2R (5)8.1.6 The depth resolution, DZ, is given by the followingequation: