1、BS ISO23812:2009ICS 71.040.40NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDSurface chemicalanalysis Secondary-ion mass spectrometry Method for depthcalibration for siliconusing multiple delta-layer referencematerialsThis British Standardwas published under the
2、authority of the StandardsPolicy and StrategyCommittee on 31 May 2009 BSI 2009ISBN 978 0 580 55765 1Amendments/corrigenda issued since publicationDate CommentsBS ISO 23812:2009National forewordThis British Standard is the UK implementation of ISO 23812:2009.The UK participation in its preparation wa
3、s entrusted to TechnicalCommittee CII/60, Surface chemical analysis.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct applicati
4、on.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 23812:2009Reference numberISO 23812:2009(E)ISO 2009INTERNATIONAL STANDARD ISO23812First edition2009-04-15Surface chemical analysis Secondary-ion mass spectrometry Method for depth calibration for silicon using
5、multiple delta-layer reference materials Analyse chimique des surfaces Spectromtrie de masse des ions secondaires Mthode pour ltalonnage de la profondeur pour le silicium laide de matriaux de rfrence couches delta multiples BS ISO 23812:2009ISO 23812:2009(E) PDF disclaimer This PDF file may contain
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8、ers were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2009 All right
9、s reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the
10、requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2009 All rights reservedBS ISO 23812:2009ISO 23812:2009(E) ISO 2009 All rights reserved iiiContents Page Foreword iv
11、Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Symbols and abbreviated terms . 1 5 Requirements on multiple delta-layer reference materials 3 6 Measurement procedures 3 7 Calibration procedures. 4 7.1 Principle of calibration . 4 7.2 Determination of sputtering ra
12、te for reference material. 5 7.3 Calibration of the depth scale for test specimens 7 7.4 Uncertainty in calibrated depth. 8 8 Expression of results . 8 8.1 Calibration under the same sputtering conditions as used for the reference material 8 8.2 Calibration using a sputtering rate different from tha
13、t of the test specimen. 9 8.3 Calibration with respect to concentration 9 9 Test report . 9 Annex A (informative) Projected range of oxygen-ion in silicon. 10 Annex B (informative) Estimations of peak shifts due to atomic mixing . 11 Annex C (informative) Estimations of peak shift due to peak coales
14、cence. 14 Annex D (informative) Derivation of uncertainty. 17 Bibliography . 19 BS ISO 23812:2009ISO 23812:2009(E) iv ISO 2009 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of
15、preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental,
16、 in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main t
17、ask of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attent
18、ion 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. ISO 23812 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee SC 6, Sec
19、ondary ion mass spectrometry. BS ISO 23812:2009ISO 23812:2009(E) ISO 2009 All rights reserved vIntroduction Secondary-ion mass spectrometry (SIMS) is a powerful method for the measurement of depth profiles of dopants in silicon. However, in the near-surface region ( 50 nm), the transient behaviours
20、of the secondary-ion yields and the sputtering rate significantly affect the profile shape1, thus it is difficult to obtain real profiles. This is caused by the accumulation of implanted primary-ion species, oxygen or caesium, which are essential for enhancing the secondary-ion yields. At the origin
21、al surface, sputtering of the specimen material occurs with a low concentration of primary-ion species, but, with the progress of sputtering, primary-ion species are incorporated on the surface and sputtered together with the specimen atoms, causing a sputtering-rate change. As a result of the sputt
22、ering-rate change in this non-equilibrium zone, a significant profile shift occurs in shallow SIMS depth profiles when a uniform sputtering rate is assumed for depth calibration. To calibrate the depth scale in such a shallow region, it is essential to evaluate the extent of the above profile shift
23、accurately. In this International Standard, multiple delta-layers are used as a reference material for depth scale calibration in the near-surface region but beyond the non-equilibrium zone, and the procedures for depth scale calibration are described. This International Standard differs from ISO 20
24、341 in its scope. ISO 20341 specifies procedures for estimating depth resolution parameters in SIMS depth profiling using multiple delta-layer reference materials, whereas this International Standard specifies a procedure for calibrating the depth scale in a shallow region. BS ISO 23812:2009BS ISO 2
25、3812:2009INTERNATIONAL STANDARD ISO 23812:2009(E) ISO 2009 All rights reserved 1Surface chemical analysis Secondary-ion mass spectrometry Method for depth calibration for silicon using multiple delta-layer reference materials 1 Scope 1.1 This International Standard specifies a procedure for calibrat
26、ing the depth scale in a shallow region, less than 50 nm deep, in SIMS depth profiling of silicon, using multiple delta-layer reference materials. 1.2 This International Standard is not applicable to the surface-transient region where the sputtering rate is not in the steady state. 1.3 This Internat
27、ional Standard is applicable to single-crystalline silicon, polycrystalline silicon and amorphous silicon. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, t
28、he latest edition of the referenced document (including any amendments) applies. ISO 18115, Surface chemical analysis Vocabulary ISO 20341, Surface chemical analysis Secondary-ion mass spectrometry Method for estimating depth resolution parameters with multiple delta-layer reference materials 3 Term
29、s and definitions For the purposes of this document, the terms and definitions given in ISO 18115 apply. 4 Symbols and abbreviated terms a intercept of regression line b slope of regression line c extra factor of regression line slope I(z) ion intensity at depth z k correction factor for the primary
30、-ion current density l number of delta-layers used for regression analysis Lsshift distance Ls(p) shift distance dependent on the definition of delta-layer peak position (see 7.2.1) BS ISO 23812:2009ISO 23812:2009(E) 2 ISO 2009 All rights reservedm maximum delta-layer number used for steady-state sp
31、uttering-rate determination n minimum delta-layer number where steady-state sputtering rate is reached r sputtering rate riaverage sputtering rate of ith silicon layer rssteady-state sputtering rate s0standard uncertainty in predicted depth without sRMand scs1standard uncertainty in depth, including
32、 sRMs2standard uncertainty in depth, including sRMand sksbstandard uncertainty in b scstandard uncertainty in c skstandard uncertainty in k sRMstandard uncertainty in depth of layers in reference material ststandard uncertainty in sputtering time t ts standard uncertainty in t T(m n 1, ) critical va
33、lue obtained from Students t-distribution table at 100 % for (m n 1) degrees of freedom t sputtering time t mean sputtering time for delta-layers tfsputtering time needed for forming crater timeasured sputtering time to reach the ith delta-layer in the ion-intensity-versus-sputtering-time profile it
34、 time predicted for ith delta-layer z sputtered depth z mean depth of delta-layers z predicted depth zaiminimum position in the valley between (i 1)th and ith delta profiles zbiminimum position in the valley between ith and (i + 1)th delta profiles zccentroid position zdoriginal delta-layer position
35、 zfcrater depth zidepth of ith delta-layer zi centroid of the ith delta-layer profile zLMlocal maximum position BS ISO 23812:2009ISO 23812:2009(E) ISO 2009 All rights reserved 3zPCpeak centre position tisputtering time for ith delta-layer zithickness of ith delta-layer SIMS secondary-ion mass spectr
36、ometry 5 Requirements on multiple delta-layer reference materials 5.1 The criteria given in 5.2 to 5.8 are appropriate for delta-layers used as the reference material. 5.2 The signal of the matrix containing the delta-layers shall not change during SIMS depth profiling so that no changes occur due t
37、o any SIMS matrix effects or due to the sputtering-rate change at delta-layers. Constant secondary-ion intensities of the matrix elements through the delta-layers are indicative of a constant matrix. 5.3 The constancy, across the specimen, of the depths of the delta-layers below the surface shall be
38、 comparable to, or better than, the required depth calibration accuracy. 5.4 The thickness of each doped delta-layer shall be sufficiently less than the projected range of the primary ions (see Annex A for examples for O2+ions) so that a small variation in the thickness does not affect the profile s
39、hape. 5.5 The spacing between adjacent delta-layers shall be sufficiently large that the peak-to-valley ratio of the adjacent delta-layer profiles shall be 10 or greater. 5.6 At least three delta-layers shall be contained in the reference material to confirm that a steady-state sputtering rate is re
40、ached in the delta-doped region. 5.7 The thickness, the position and the interface roughness of the delta-layers shall be determined by cross-sectional transmission electron microscopy, grazing incidence X-ray reflectivity, medium-energy ion scattering spectrometry or another appropriate method. 5.8
41、 The thickness of the surface oxide layer shall be comparable with that of the native oxide layer on the crystalline-silicon surface. The oxide thickness shall be determined by a valid measurement method. 6 Measurement procedures 6.1 For precise calibration of the depth scale, multiple delta-layer r
42、eference materials shall be measured with test specimens using the same energy and incident angle of the primary ions. Once the sputtering rate, the depth correction factor and the shift distance (see 7.2.3) are determined for a specific set of ion-irradiation conditions (for energy, angle of incide
43、nce, ion current and scan area), the predetermined values can be used for the determination of the depth scale. It should be noted that the depth scale can have a deviation due to limited reproducibility of the sputtering rate (see 6.5). 6.2 For adjustment and optimization of the secondary-ion mass
44、spectrometer settings, the analysis conditions, such as ion energy, ion species, ion current, secondary-ion polarity, primary-ion scan region, analysed region, stability of the primary-ion current, specimen introduction and detected secondary ions, shall be set in accordance with the manufacturers i
45、nstruction or a local documented procedure. 6.3 The SIMS depth profile of multiple delta-layer reference materials shall be measured from the surface to near the interface between the multiple delta-layers and the substrate, or to a depth described in the instructions for the reference materials. Ho
46、wever, if a change in secondary-ion intensity occurs due to surface roughness induced by ion bombardment before the above depth is reached, depth profiling shall be terminated before the surface roughening occurs. BS ISO 23812:2009ISO 23812:2009(E) 4 ISO 2009 All rights reserved6.4 The measurement c
47、onditions, such as the primary-ion intensity and scanning area, shall be determined so that there are more than 20 measurement points for a delta-layer. 6.5 When confirming reproducibility, the SIMS depth profile of a multiple delta-layer reference material shall be measured three times, and the rep
48、eatability of the profile shall be checked. The time to each position of the delta-layers shall be reproduced with the accuracy of the analytical requirement. If the SIMS profile shapes of the multiple delta-layer reference material are not reproducible, the instrument performance shall be checked f
49、or items such as the drift of primary-ion current and the scan uniformity. 6.6 The SIMS depth profile of test specimens shall be measured using the same measurement conditions as those used for the multiple delta-layer reference materials. If necessary, the primary-ion current density can be changed by changing the primary-ion current and/or the primary-ion scan area. 7 Calibration procedures 7.1 Principle of calibration 7.1.1 This International Standard gives equations for calibrating the depth sc
