1、 ISO 2013 Surface chemical analysis Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods Analyse chimique des surfaces Approche fondamentale pour la dtermination de la rsolution latrale et de la nettet par des mthodes base de faisceau TECHNICAL REPORT ISO
2、/TR 19319 Second edition 2013-03-15 Reference number ISO/TR 19319:2013(E) ISO/TR 19319:2013(E)ii ISO 2013 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by a
3、ny 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 office Case postale 56 CH-1211
4、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 ISO/TR 19319:2013(E) ISO 2013 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 T erms and definitions . 1 3 Symbols and abbreviated terms . 4 4 Determ
5、ination of lateral resolution and sharpness by imaging of stripe patterns 7 4.1 Theoretical background 7 4.2 Determination of the line spread function and the modulation transfer function by imaging of a narrow stripe 21 4.3 Determination of the edge spread function (ESF) by imaging a straight edge
6、.41 4.4 Determination of lateral resolution by imaging of square-wave gratings 56 5 Physical factors affecting lateral resolution, analysis area and sample area viewed by the analyser in AES and XPS .96 5.1 General information 96 5.2 Lateral resolution of AES and XPS .97 5.3 Analysis area .104 5.4 S
7、ample area viewed by the analyser 106 6 Measurements of analysis area and sample area viewed by the analyser in AES and XPS 107 6.1 General information .107 6.2 Analysis area .108 6.3 Sample area viewed by the analyser 109 Annex A (informative) Reduction of image period for 3-stripe gratings .110 Bi
8、bliography .113 ISO/TR 19319:2013(E) Foreword ISO (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
9、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, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotech
10、nical 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 task of technical committees is to prepare International Standards. Draft International Standards adopted by t
11、he 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. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is
12、normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are
13、considered to be no longer valid or useful. Attention 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/TR 19319 was prepared by Technical Committee ISO/TC 2
14、01, Surface chemical analysis, Subcommittee SC 2, General procedures. This second edition cancels and replaces the first edition (ISO/TR 19319:2003), which has been technically revised.iv ISO 2013 All rights reserved ISO/TR 19319:2013(E) Introduction Surface-analytical techniques such as SIMS, AES a
15、nd XPS enable imaging of surfaces. The most relevant parameter of element or chemical maps and line scans is the lateral resolution, also called image resolution. 1)Therefore well defined and accurate procedures for the determination of lateral resolution are required. Those procedures together with
16、 appropriate test specimen are basic preconditions for comparability of results obtained by imaging surface-analytical methods and performance tests of instruments as well. This Technical Report is intended to serve as a basis for the development of International Standards. Nowadays there is some co
17、nfusion in the community in the understanding of the term “lateral resolution”. Definitions originating from different fields of application and different communities of users can be found in the literature. Unfortunately they are inconsistent in many cases. As a result, values of “lateral resolutio
18、n” published by manufacturers and users having been derived by using different definitions and/or determined by different procedures cannot be compared to each other. It is the intention of this Technical Report to basically describe different approaches for the characterization of lateral resolutio
19、n including their interrelations. The term resolution was introduced with respect to the performance of microscopes by Ernst Abbe. 1Later on it was applied to spectroscopy by Lord Rayleigh. 2It is based on the diffraction theory of light and the original definition of lateral resolution as “the mini
20、mum spacing at which two features of the image can be recognised as distinct and separate” is in common use in the light and electron microscopy communities as documented in the standard ISO 22493:2008. 3 However, in the surface analysis community a very different approach, the “knife edge method”,
21、is the most popular one for the determination of lateral resolution. This method is based on evaluation of an image or of a line scan over a straight edge. Here lateral resolution is characterized by parameters describing the steepness of the edge spread function ESF. The standard “ISO 18516:2006 Su
22、rface Chemical Analysis Auger electron spectroscopy and X-ray photoelectron spectroscopy Determination of lateral resolution” 4is limited to this approach. But the ESF and corresponding rise parameters D x-(1-x)are more related to image sharpness than to lateral resolution which refers to two separa
23、ted features. The reason why the original meaning of resolution is not commonly implemented in the common practice in surface analysis is the lack of suitable test specimens having the required features in the sub-m range. However, recently a new type of test specimen was developed featuring a serie
24、s of flat square-wave gratings characterized by chemical contrast and different periods. 5,6Such test specimens may enable an implementation of the original definition of lateral resolution into practical approaches in surface chemical analysis. Having solved the problem of availability of appropria
25、te test specimens another problem has to be solved: The establishment of a criterion for whether two features are separated or not. The Rayleigh criterion 2was developed for diffraction optics and its application in imaging surface analysis is not straightforward. The Sparrow criterion 7defines a re
26、solution threshold exclusively by the existence of a minimum between two maxima. Actually, for practical imaging in surface analysis, noise is a relevant feature especially at the limit of resolution. Therefore the Sparrow criterion will fail to solve the problem. The solution is to develop a resolu
27、tion criterion relying on the detection of a minimum between two features but additionally considering noise effects. The lateral resolution of imaging systems is strongly related to a number of functions describing the formation of images: the modulation transfer function, the contrast transfer fun
28、ction, the point spread function, 1) The term “image resolution” is used in the microscopy community whereas in the surface analysis community the term “lateral resolution” is common practice to distinguish it from “depth resolution”. ISO 2013 All rights reserved v ISO/TR 19319:2013(E) the line spre
29、ad function and and the edge spread function. Those functions may be utilized to describe the performance of optical instruments and instruments used for imaging in surface analysis as well. In particular the contrast transfer function has been used successfully for the benefit of the determination
30、of lateral resolution of imaging instruments in surface analysis. Section 4 of this report describes the basics of procedures for the analysis of images of stripe patterns, narrow stripes and step transitions. A comparison of all procedures related to lateral resolution and sharpness is given in 4.1
31、.7. Section 5 of the report describes physical factors affecting lateral resolution, analysis area and sample area viewed by the analyser in Auger electron spectroscopy and X-ray photoelectron spectroscopy. Section 6 of the report gives guidance on the determination of sample area viewed by the anal
32、yser in applications of Auger electron spectroscopy and X-ray photoelectron spectroscopy.vi ISO 2013 All rights reserved TECHNICAL REPORT ISO/TR 19319:2013(E) Surface chemical analysis Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods 1 Scope This Tech
33、nical Report describes: a) Functions and their relevance to lateral resolution: 1) Point spread function (PSF) see 4.1.1 2) Line spread function (LSF) see 4.1.2 3) Edge spread function (ESF) see 4.1.3 4) Modulation transfer function (MTF) see 4.1.4 5) Contrast transfer function (CTF) see 4.1.5. b) E
34、xperimental methods for the determination of lateral resolution and parameters related to lateral resolution: 1) Imaging of a narrow stripe see 4.2 2) Imaging of a sharp edge see 4.3 3) Imaging of square-wave gratings see 4.4. c) Physical factors affecting lateral resolution, analysis area and sampl
35、e area viewed by the analyser in Auger electron spectroscopy and X-ray photoelectron spectroscopy see Clauses 5 and 6. 2 T erms a nd definiti ons For the purposes of this document, the following terms and definitions apply. 2.1 analysis areatwo-dimensional region of a sample surface measured in the
36、plane of that surface from which the entire analytical signal or a specified percentage of that signal is detected SOURCE: ISO 18115:2010, definition 5.8 2.2 contrast transfer function CTF ratio of the image contrast to the object contrast of a square-wave pattern as a function of spatial frequency
37、Note 1 to entry: In this document the contrast transfer function CTF has been used also with an abscissa expressed in terms of w LSF /P and is called the generalized contrast transfer function in those cases (cf. 4.4.3.2). w LSFis the full width at half maximum of the line spread function LSF Note 2
38、 to entry: In transmission electron microscopy and other phase sensitive methods the term contrast transfer function is used with a different meaning considering amplitude as well as phase information. ISO 2013 All rights reserved 1 ISO/TR 19319:2013(E) 2.3 cut-off frequency of the contrast transfer
39、 function lowest spatial frequency at which the contrast transfer function CTF equals to zero Note 1 to entry: In this document the spatial frequency at which the contrast transfer function CTF equals the threshold of resolution under consideration of noise (cf. 4.4.3.3) is called effective cut-off
40、frequency of the contrast transfer function. 2.4 edge spread function ESF normalized spatial signal distribution in the linearized output of an imaging system resulting from imaging a theoretical infinitely sharp edge SOURCE: ISO 12231:2012, definition 3.43 2.5 effective cut-off frequency see cut-of
41、f frequency of the contrast transfer function, Note 1 to entry 2.6 effective lateral resolution minimum spacing of two stripes of a square-wave grating at which the dip of signal intensity between two maxima of the image is at least 4 times the reduced noise NR 2.7 generalized contrast transfer func
42、tion see contrast transfer function, Note 1 to entry 2.8 image contrast c i c i= (I max I min )/(I max +I min ) = I/2 I mean(Michelson contrast), where I max , I minand I meanare signal intensities in the image Note 1 to entry: Other definitions (not used in this document) include: difference in sig
43、nal between two arbitrarily chosen points of interest (P 1 , P 2 ) in the image field, normalized by the maximum possible signal available under the particular operating conditions, (ISO 22493:2008, definition 5.3). Note 2 to entry: With respect to aperiodic patterns the Weber contrast c = (I I b )/
44、I bis used to quantify the contrast between a feature with the signal intensity I and the background signal intensity I b . Note 3 to entry: With respect to periodic object patterns, the terms contrast and modulation often are used synonymously. 2.9 image resolution minimum spacing at which two feat
45、ures of the image can be recognised as distinct and separate SOURCE: ISO 22493:2008, definition 7.2 2.10 lateral resolution minimum distance between two features (in this document the period of a square wave grating) which can be imaged in that way, that the dip between two maxima is at least 4 time
46、s the reduced noise NR(cf. 4.4.2.3) Note 1 to entry: This definition is in accordance with the definition of image resolution given in ISO 22493:2008. Note 2 to entry: This definition is different from the definition of lateral resolution given in ISO 18115:2010.2 ISO 2013 All rights reserved ISO/TR
47、 19319:2013(E) 2.11 linear system system whose response is proportional to the level of input signals SOURCE: ISO 9334:1995, definition 3.1 2.12 line spread function LSF normalized spatial signal distribution in the linearized output of an imaging system resulting from imaging a theoretical infinite
48、ly thin line SOURCE: ISO 12231:2012, definition 3.94 2.13 modulation m measure of degree of variation in a sinusoidal signal SOURCE: ISO 9334:1995, definition 3.17 2.14 modulation transfer function MTF ratio of the image modulation to the object modulation as a function of spatial frequency SOURCE:
49、ISO/IEC 19794-6:2011, definition 4.7 2.15 noise time-varying disturbances superimposed on the analytical signal with fluctuations leading to uncertainty in the signal intensity Note 1 to entry: An accurate measure of noise can be determined from the standard deviation of the fluctuations. Visual or other estimates, such as peak to peak noise in a spectrum or in a line scan, may be useful as semiquantitative measures of noise. SOURCE
