1、Designation: E1438 11Standard Guide forMeasuring Widths of Interfaces in Sputter Depth ProfilingUsing SIMS1This standard is issued under the fixed designation E1438; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 guide provides the SIMS analyst with a method fordetermining the width of interfaces from SIMS sputtering dataobtained
3、 from analyses of layered specimens (both organic andinorganic). This guide does not apply to data obtained fromanalyses of specimens with thin markers or specimens withoutinterfaces such as ion-implanted specimens.1.2 This guide does not describe methods for the optimiza-tion of interface width or
4、the optimization of depth resolution.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 lim
5、itations prior to use.2. Referenced Documents2.1 ASTM Standards:2E673 Terminology Relating to Surface Analysis3. Terminology3.1 Definitions:3.1.1 See Terminology E673 for definitions of terms used inSIMS.4. Summary of Guide4.1 This guide will allow interface widths to be calculatedfrom plots of SIMS
6、 secondary ion intensity versus time that areacquired during sputtering of layered specimens. It assumesthat a primary ion beam with a stable current density is beingused. Briefly, these plots are obtained in the following fashion:an ion beam of a particular ion species, ion energy, and angleof inci
7、dence is used to bombard a sample. The beam is rasteredor defocused so as to attempt to produce uniform currentdensity in the analyzed area, that is defined by means ofmechanical or electronic gating. The intensity of one or moresecondary ions is monitored with respect to time as sputteringcontinues
8、.4.2 The interface width is then determined from the second-ary ion intensity versus time data according to an arithmeticmodel described in the Procedure section. A measurement ofthe thickness of the layer overlying the interface is required.This measurement may be performed by another analyticaltec
9、hnique.5. Significance and Use5.1 Although it would be desirable to measure the extent ofprofile distortion in any unknown sample by using a standardsample and this guide, measurements of interface width (pro-file distortion) can be unique to every sample composition (1,2).3This guide, describes a m
10、ethod that determines the uniquewidth of a particular interface for the chosen set of operatingconditions. It is intended to provide a method for checking onproper or consistent, or both, instrument performance. Periodicanalysis of the same sample followed by a measurement of theinterface width, in
11、accordance with this guide, will providethese checks.5.2 The procedure described in this guide is adaptable toany layered sample with an interface between layers in whicha nominated element is present in one layer and absent from theother. It has been shown that for SIMS in particular (3, 4) andfor
12、surface analysis in general (5, 6), only rigorous calibrationmethods can determine accurate interface widths. Such proce-dures are prohibitively time-consuming. Therefore the inter-face width measurement obtained using the procedure de-scribed in this guide may contain significant systematic error(7
13、). Therefore, this measure of interface width may have norelation to similar measures made with other methods. How-ever, this does not diminish its use as a check on proper orconsistent instrument performance, or both.5.3 This guide can be used for both elemental and moleculardepth profiles, provide
14、d that the materials have constant sputterrates throughout the depth of the overlayer, and minimal1This guide is under the jurisdiction of ASTM Committee E42 on SurfaceAnalysis and is the direct responsibility of Subcommittee E42.06 on SIMS.Current edition approved Nov. 1, 2011. Published December 2
15、011. Originallyapproved in 1991. Last previous edition approved in 2006 as E1438 06. DOI:10.1520/E1438-11.2For 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 standa
16、rds Document Summary page onthe ASTM website.3The boldface numbers given in parentheses refer to a list of references at theend of this guide.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.interlayer mixing is occurring. For more de
17、tailed informationregarding measurements of interface widths during organicdepth profiling, please see Mahoney (8).6. Apparatus6.1 The procedure described in this guide can be used todetermine an interface width from data obtained with virtuallyany SIMS instrument.6.2 Use of the interface width meas
18、urement from a layeredspecimen as a check on proper or consistent instrumentperformance, or both, does not assume that the sample ofinterest contains no interface roughness. Rather, it assumes thatthe interface roughness is consistent from one analyzed area tothe next. Any layered sample that meets
19、this criterion issuitable for the use intended by this guide.7. Procedure7.1 This procedure for measurement of depth resolution isbased on the amount of time required for the signal of one ofthe major elements of the layer overlying the interface to bereduced from 84 to 16 % of its average intensity
20、 in theoverlying layer. The ratio of this interface sputtering time tothat of the sputtering time of the overlayer is equated to theratio of their respective thicknesses in order to obtain themeasurement of interface thickness. This is expressed in theform of the following equation (refer to Fig. 1)
21、:Dz 5 Dt/t!z (1)where:Dz = interface width,Dt = sputtering time for decrease from 84 to 16 % of thesignal intensity,t = time required to sputter through overlayer, from t =0until t is equal to the time at which the major elementreaches 50 % of its value in the overlayer, andz = thickness of overlaye
22、r.7.1.1 The measurement of sputter time (t) for the interfacialregion and for the overlying layer thickness should be acquiredgraphically from the plot of secondary ion signal versus time.7.1.2 The thickness of the overlayer (z) is commonlyobtained from a post-profile crater measurement and assuming
23、a constant sputter rate. The thicknesses of layers in a multilay-ered profile are only approximated by this procedure. A moreaccurate thickness value for the overlayer is obtained byhalting the sputtering at the interface, and obtaining a cratermeasurement. Alternatively, other techniques may be use
24、d tomeasure the overlying layer. Some possible techniques thatmay be used include optical interferometry, ellipsometry,selective chemical etching followed by profilometry, andspectroscopic methods such as Rutherford BackscatteringSpectrometry (RBS), X-ray Fluorescence (XRF), and AngleResolved X-ray
25、Photoelectron Spectroscopy (ARXPS).7.1.3 Additional considerations for molecular depth profil-ing: (1) interfaces of molecular samples on silicon (Si) sub-strates are ill-defined due to the large differences in sputterproperties between organic/inorganic interfaces. These differ-ences can cause prim
26、ary ion recoil and Si rebounding. This cancause increased damage or drastic changes, or both, in sputterrates of the organic material at the interface. Therefore, it isimpossible to determine accurate sputter rates in this region,unless they are measured directly. It is recommended that anydiscussio
27、n of interface widths in such systems should be forrelative comparisons only. (2) For organic samples, one mayuse either the polymer signal decay or the rise in the substratesignal to describe the interface width, depending on theparticular system, experimental conditions, chemistries andartifacts o
28、bserved for your selected organic system. For moreinformation, see Mahoney (8).FIG. 1 Measurement of Interface Width, Dz,fromaPlotofSIMSIntensity Versus Ion Bombardment TimeE1438 112REFERENCES(1) Wittmaack, K., “Influence of the impact angle on the depth resolutionand the sensitivity in the SIMS dep
29、th profiling using a cesium ionbeam,” Journal of Vacuum Science Technology, Vol A3, 1985, p.1350.(2) Boudewijn, P.R., Leys, M.R., and Roozeboom, F., “SIMS analysis ofAlxGa1-xas/gaas layered structures grown by metal-organic vapourphase Epitaxy,” Surface Interface Analysis, Vol 9, No. 5, 1986, p.303.
30、(3) Galuska, A.A., “SIMS V, Proceedings of the Fifth InternationalConference,” Springer Verlag: New York, 1986, p. 363.(4) Galuska, A.A., and Morrison, G.H., “Point-by-point matrix effectcalibration for the quantitative analysis of superlattices by secondaryion mass spectrumetry,” Analytical Chemist
31、ry, Vol 56, No. 11984, p.74.(5) Kirchhoff, W.H., Chambers, G.P., and Fine, J., “An analytical expres-sion for describing Auger sputter depth profile shapes of interfaces,”Journal of Vacuum Science Technology, Vol A4, 1986, p. 1666.(6) Fine, J., Lindfors, P.A., Gorman, M.E., Gerlach, R.L., Navinsek,
32、B.,Mitchell, D.F., and Chambers, G.P., “Interface depth resolution ofAuger sputter profiled Ni/Cr interfaces: Dependence on ion bombard-ment parameters,” Journal of Vacuum Science Technology, Vol A3,1985, p. 1413.(7) Hofmann, S., and Sanz, J.M., Thin Film and Depth Profile Analysis,H. Oechsner, ed.,
33、 Springer-Verlag: New York, 1984, pp. 141158.(8) Mahoney, C.M., “Cluster secondary ion mass spectrometry of poly-mers and related materials,” Mass Spectrometry Reviews, Vol 29, No.9, 2010, pp. 247293.ASTM International takes no position respecting the validity of any patent rights asserted in connec
34、tion with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsib
35、le technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful con
36、sideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100
37、Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).E1438 113
