BS ISO 16531-2013 Surface chemical analysis Depth profiling Methods for ion beam alignment and the associated measurement of current or current density for depth profiling in AES a.pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 16531:2013Surface chemical analysis Depth profiling Methods forion beam alignment and theassociated measurement ofcurrent or current density fordepth profiling in AES and

2、XPSBS ISO 16531:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 16531:2013.The UK participation in its preparation was entrusted to TechnicalCommittee CII/60, Surface chemical analysis.A list of organizations represented on this committee can beobtained on

3、 request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 74315 3ICS 71.040.40Compliance with a Briti

4、sh Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 May 2013.Amendments issued since publicationDate Text affectedBS ISO 16531:2013 ISO 2013Surface chemical analysis Depth profiling Metho

5、ds for ion beam alignment and the associated measurement of current or current density for depth profiling in AES and XPSAnalyse chimique des surfaces Profilage dpaisseur Mthodes dalignement du faisceau dions et la mesure associe de densit de courant ou de courant pour le profilage dpaisseur en AES

6、et XPSINTERNATIONAL STANDARDISO16531First edition2013-06-01Reference numberISO 16531:2013(E)BS ISO 16531:2013ISO 16531:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized

7、 otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright of

8、ficeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 16531:2013ISO 16531:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms, definitio

9、ns, symbols and abbreviated terms . 14 System requirements . 24.1 General . 24.2 Limitations 25 Ion beam alignment methods . 35.1 General . 35.2 Important issues to be considered prior to ion beam alignment 35.3 Alignment using circular-aperture Faraday cup 65.4 Alignment using elliptical-aperture F

10、araday cup 95.5 Alignment using images from ion-induced secondary electrons during ion beam rastering 95.6 Alignment in X-ray photoelectron microscope/photoelectron imaging system .115.7 Alignment by observing direct ion beam spot or crater image during and/or after ion sputtering 125.8 Alignment by

11、 observing phosphor sample 136 When to align and check ion beam alignment 13Annex A (informative) Comparison of AES depth profiles with good/poor ion beam alignment 14Annex B (informative) Alignment using cup with co-axial electrodes .16Bibliography .18BS ISO 16531:2013ISO 16531:2013(E)ForewordISO (

12、the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical commi

13、ttee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotec

14、hnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted

15、 in accordance with the editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directivesAttention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Deta

16、ils of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received. www.iso.org/patentsAny trade name used in this document is information given for the convenience of users and does not constitute an endorsem

17、ent.The committee responsible for this document is ISO/TC 201, Surface chemical analysis, Subcommittee SC 4, Depth profiling.iv ISO 2013 All rights reservedBS ISO 16531:2013ISO 16531:2013(E)IntroductionIn surface chemical analysis with AES (Auger electron spectroscopy) and XPS (X-ray photoelectron s

18、pectroscopy), ion sputtering has been extensively incorporated for surface cleaning and for the in-depth characterization of layered structures in many devices and materials. Currently, ultra-thin films of 10 nm thickness are increasingly used in modern devices and so lower energy ions are becoming

19、more important for depth profiling. For reproducible sputtering rates and for good depth resolution, it is important to align the ion beam at the optimal position. This optimization becomes increasingly critical as better and better depth resolutions are required. It is not necessary to conduct a be

20、am alignment routinely but it is necessary to align the beam when instrument parameters change as a result, for example, from replacement of ion-gun filaments or from an instrument bake-out. During the beam alignment, care must be taken not to sputter or otherwise affect specimens for analysis on th

21、e sample holder. Instruments have different facilities to conduct alignment and seven methods are described to ensure that most analysts can conduct at least one method. Two of these methods are also useful for measuring the ion beam current or the current density important when measuring sputtering

22、 yields and for measuring sputtering rate consistency. With commercial instruments, the manufacturer may provide a method and equipment to conduct the beam alignment. If this is adequate, the methods described here may not be necessary but may help to validate that method.ISO 146061describes how the

23、 depth resolution may be measured from a layered sample and used to monitor whether the depth profiling is adequate, properly optimized or behaving as intended. That method, from the instrumental setup to the depth resolution evaluation via in-depth measurement is, however, time-consuming and so the

24、 present, quicker procedure is provided to ensure that the ion beam is properly aligned as the first step to using ISO 14606 or for more routine checking. ISO 2013 All rights reserved vBS ISO 16531:2013BS ISO 16531:2013Surface chemical analysis Depth profiling Methods for ion beam alignment and the

25、associated measurement of current or current density for depth profiling in AES and XPS1 ScopeThis International Standard specifies methods for the alignment of the ion beam to ensure good depth resolution in sputter depth profiling and optimal cleaning of surfaces when using inert gas ions in Auger

26、 electron spectroscopy and X-ray photoelectron spectroscopy. These methods are of two types: one involves a Faraday cup to measure the ion current; the other involves imaging methods. The Faraday cup method also specifies the measurements of current density and current distributions in ion beams. Th

27、e methods are applicable for ion guns with beams with a spot size below 1 mm in diameter. The methods do not include depth resolution optimization.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application

28、. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) appliesISO 18115-1, Surface chemical analysis Vocabulary Part 1: General terms and terms used in spectroscopy3 Terms, definitions, symbols and abbr

29、eviated termsFor the purposes of this document, the terms and definitions given in ISO 18115-1 and the following symbols and abbreviated terms apply.A Area of Faraday cup apertureA0Area of ion beam raster in sample planeARRaster area at a known orientation to the ion beamB Ion beam broadening parame

30、ter equal to ratio Iouter/IinnerC CurrentCD Current densityD Ion dose rate at the sampleF Ion fluence rate delivered by ion gunFC Faraday cupFWHM Full width at the half maximumI Rastered ion beam current measured in aperture of Faraday cupI0Stationary, small diameter ion beam current measured in ape

31、rture of Faraday cupIinnerIon current measured at inner electrode of co-axial cupINTERNATIONAL STANDARD ISO 16531:2013(E) ISO 2013 All rights reserved 1BS ISO 16531:2013ISO 16531:2013(E)IouterIon current measured at outer electrode of co-axial cupISBeam current as measured into dark region in the me

32、thod specified in 5.5J Current density in ion beam measured per unit area of sample surfaceX Position of ion beam on x-axis set by ion gun controllerX0Aligned position on x-axis of ion beam set by ion gun controllerY Position of ion beam on y-axis set by ion gun controllerY0Aligned position on y-axi

33、s of ion beam set by ion gun controller Angle of incidence of ion beam with respect to sample surface normalaAngle of incidence of ion beam with respect to Faraday cup surface normal in usual posi-tionbMinimized angle of incidence of ion beam with respect to Faraday cup surface normalAES Auger elect

34、ron spectroscopyOMI Optical microscope imageSEI Secondary electron imageSEM Secondary electron microscopeXPS X-ray photoelectron spectroscopy4 System requirements4.1 GeneralThis International Standard is applicable to the focusable ion gun for sputtering with inert gases that is usually supplied wit

35、h most of AES and XPS instruments or available from after market suppliers. The beam size or raster area of the ion beam shall be larger than and uniform over the analysis area. Seven alternative methods of ion beam alignment are described that require the equipment to have provision for the measure

36、ment of the ion current, or for detecting excited secondary signals, or an optical microscope aligned at the analytical point. Depending on the equipment available, measurements of increasing sophistication may be made. The methods for measuring the ion beam current involve measurement by a circular

37、-aperture Faraday cup, elliptical-aperture Faraday cup or a co-axial electrode cup. The methods involving the excited secondary signals are categorized by ion/electron-induced secondary electrons or emitted photons that are detected with a secondary electron detector, an optical microscope or a phos

38、phor screen.To conduct the relevant surface analysis, the electron energy analyser, the analysis probe beam and the ion beam need to be focused and aligned correctly on the same analysis point or area to be analysed. To apply this International Standard, the electron energy analyser and the analysis

39、 probe beam shall already be aligned to the optimum position using the manufacturers or in house documented procedure.4.2 LimitationsThis International Standard is an important part of the setting up of depth profiling generally; nevertheless, depending on the material of the sample and its structur

40、e, there are several depth profiling 2 ISO 2013 All rights reservedBS ISO 16531:2013ISO 16531:2013(E)procedures that may be applied to achieve the best depth resolution, not all of which are aided by this International Standard. Some of the most popular procedures area) ion bombardment of fixed posi

41、tion samples at angles of incidence in the range of 060 with respect to the surface normal,b) ion bombardment at grazing angles of incidence,c) sample rotation during ion bombardment,d) simultaneous ion bombardment applying two ion guns, ande) sample rotation and grazing angle of incidence for ion b

42、ombardment.This International Standard will assist in the use of procedure a). Some aspects may relate to the other procedures but further considerations may be required that are not necessarily included in this International Standard.5 Ion beam alignment methods5.1 GeneralThis International Standar

43、d describes not all but seven simple methods for ion beam alignment, easily applied. These methods and a summary of their advantages are set out in Table 1. Also indicated are which methods are best for ion beam current or current density measurement.Each method has different advantages and requires

44、 different instrumental capabilities. The analyst needs to select the method based on requirements and equipment capabilities. Some issues depend on the raster size of the ion beam. A small raster is good, since little material is consumed or sputter deposited in the spectrometer. Additionally, for

45、industrial samples, the material to be profiled may only occupy a small area. A very small raster is possible in AES where the electron beam is small and some users may deliberately use higher ion beam energies where ion beams tend to be better focused to obtain small sputtered areas with a faster s

46、puttering rate. In these cases, and for systems with small-area XPS analysis, particular care needs to be taken with alignment. For broader ion beams, such as for some XPS instruments, the alignment accuracy may be more relaxed. If more than one method is suitable, tests with each will show which is

47、 most convenient for the sputtering conditions intended.The effects of good and poor ion beam alignment in sputter depth profiling are illustrated in Annex A.General precautions are given in 5.2. If analysts wish to align the beam and measure the ion beam current or current density, or change the io

48、n beam energy, they can choose one of the two methods that use a Faraday cup. The alignment methods specified in 5.3 and 5.4 are those using Faraday cups with a circular aperture and an elliptical aperture, respectively; whereas Annex B introduces a method using co-axial electrodes giving measuremen

49、ts proportional to the ion current or current density. If analysts wish to align the beam and not measure the ion current or current density, they can align the beam using images from secondary electrons or ions excited by ions or primary electrons, or an optical image, or by ion-induced luminescence, using the methods specified in 5.5, 5.6, 5.7 and 5.8, respectively. The method chosen depends on the capability and facility of the instrument used. Clause 6 describes when to conduct the ion beam alignment.5.2 Important issue