BS ISO 16413-2013 Evaluation of thickness density and interface width of thin films by X-ray reflectometry Instrumental requirements alignment and positioning data collection data .pdf

1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 16413:2013Evaluation of thickness, densityand interface width of thinfilms by X-ray reflectometry Instrumental requirements,alignment and positioning,data collection, data

2、 analysisand reportingBS ISO 16413:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 16413:2013. The UK participation in its preparation was entrusted to TechnicalCommittee CII/60, Surface chemical analysis.A list of organizations represented on this committ

3、ee can beobtained on 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 2013 ISBN 978 0 580 73016 0 ICS 35.240.70;

4、 71.040.40 Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 March 2013. Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 16413:2013 ISO 2013

5、Evaluation of thickness, density and interface width of thin films by X-ray reflectometry Instrumental requirements, alignment and positioning, data collection, data analysis and reportingvaluation de lpaisseur, de la densit et de la largeur de linterface des films fins par rflectromtrie de rayons X

6、 Exigences instrumentales, alignement et positionnement, rassemblement des donnes, analyse des donnes et rapportINTERNATIONAL STANDARDISO16413First edition2013-02-15Reference numberISO 16413:2013(E)BS ISO 16413:2013ISO 16413:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013

7、All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 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

8、 from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase 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 16413:2013ISO 16413:2013(E) ISO 2013 All righ

9、ts reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Terms, definitions, symbols and abbreviated terms . 12.1 Terms and definitions . 12.2 Symbols and abbreviated terms. 43 Instrumental requirements, alignment and positioning guidelines 43.1 Instrumental requirements for the scanning me

10、thod 43.2 Instrument alignment . 93.3 Specimen alignment . 94 Data collection and storage 114.1 Preliminary remarks . 114.2 Data scan parameters . 114.3 Dynamic range 114.4 Step size (peak definition) . 124.5 Collection time (accumulated counts) . 124.6 Segmented data collection . 124.7 Reduction of

11、 noise . 134.8 Detectors . 134.9 Environment 134.10 Data storage 135 Data analysis 145.1 Preliminary data treatment 145.2 Specimen modelling 145.3 Simulation of XRR data . 165.4 General examples . 165.5 Data fitting . 196 Information required when reporting XRR analysis .216.1 General 216.2 Experime

12、ntal details . 216.3 Analysis (simulation and fitting) procedures 226.4 Methods for reporting XRR curves . 23Annex A (informative) Example of report for an oxynitrided silicon wafer .26Bibliography .30BS ISO 16413:2013ISO 16413:2013(E)ForewordISO (the International Organization for Standardization)

13、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 committee has been established has the right to be repres

14、ented 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 electrotechnical standardization.International Standards are d

15、rafted 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 the technical committees are circulated to the member bodies for voting. Publication as an International S

16、tandard requires approval by at least 75 % of the member bodies casting a vote.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 16413 was prepared

17、by Technical Committee ISO/TC 201, Surface chemical analysis.iv ISO 2013 All rights reservedBS ISO 16413:2013ISO 16413:2013(E)IntroductionX-Ray Reflectometry (XRR) is widely applicable to the measurement of thickness, density and interface width of single layer and multilayered thin films which have

18、 thicknesses between approximately 1 nm and 1 m, on flat substrates, provided that the layer, equipment and X-ray wavelength are appropriate. Interface width is a general term; it is typically composed of interface or surface roughness and/or density grading across an interface. The specimen needs t

19、o be laterally uniform under the footprint of the X-ray beam. In contrast with typical surface chemical analysis methods which provide information of the amount of substance and need conversion to estimate thicknesses, XRR provides thicknesses directly traceable to the unit of length. XRR is very po

20、werful method to measure the thickness of thin film with SI traceability.The key requirements for equipment suitable for collecting specular X-ray reflectivity data of high quality, and the requirements for specimen alignment and positioning so that useful, accurate measurements may be obtained are

21、described in Clause 3.The key issues for data collection to obtain specular X-ray reflectivity data of high quality, suitable for data treatment and modelling are described in Clause 4. The collection of the data is traditionally conducted by running single measurements under direct operator data in

22、put. However, recently data are often collected by instructing the instrument to operate in multiple runs. In addition to the operator mode, data can be collected making use of automated scripts, when available in the software program controlling the instrument.The principles for analysing specular

23、XRR data in order to obtain physically meaningful material information about the specimen are described in Clause 5. While specular XRR fitting can be a complex process, it is possible to simplify the implementation for quality assurance applications to the extent where it can be transparent to the

24、user. There are many software packages, both proprietary and non-proprietary available for simulation and fitting of XRR data. It is beyond the scope of this document to describe details of theories and algorithms. Where appropriate, references are given for the interested reader.The information req

25、uired when reporting on XRR experiments is listed in Clause 6. A brief review of the possible ways to present XRR data and results is given and, when more than one option is available, the preferred one is indicated.This document is not a textbook, it is a standard for performing XRR measurements an

26、d analysis. For a full explanation of the technique, please consult appropriate references e.g. D. Keith Bowen and Brian K. Tanner, “X-Ray Metrology in Semiconductor Manufacturing”, Taylor and Francis, London (2006); M. Tolan, “X-ray Reflectivity from Soft Matter Thin Films“, Springer Tracts in Mode

27、rn Physics vol. 148 (1999); U. Pietsch, V. Holy and T. Baumbach, “High Resolution X-Ray Scattering from Thin Films to Lateral Nanostructures”, Springer (2004); J. Daillant and A. Gibaud, “X-ray and Neutron Reflectivity: Principles and Applications”, Springer (2009).Note that proprietary techniques a

28、re not described in this International Standard.Safety aspects related to the use of X-ray equipment are not considered in this document. During the measurements, the adherence to relevant safety procedures as imposed by law are the responsibilities of the user. ISO 2013 All rights reserved vBS ISO

29、16413:2013BS ISO 16413:2013Evaluation of thickness, density and interface width of thin films by X-ray reflectometry Instrumental requirements, alignment and positioning, data collection, data analysis and reporting1 ScopeThis International Standard specifies a method for the evaluation of thickness

30、, density and interface width of single layer and multilayered thin films which have thicknesses between approximately 1 nm and 1 m, on flat substrates, by means of X-Ray Reflectometry (XRR).This method uses a monochromatic, collimated beam, scanning either an angle or a scattering vector. Similar c

31、onsiderations apply to the case of a convergent beam with parallel data collection using a distributed detector or to scanning wavelength, but these methods are not described here. While mention is made of diffuse XRR, and the requirements for experiments are similar, this is not covered in the pres

32、ent document.Measurements may be made on equipment of various configurations, from laboratory instruments to reflectometers at synchrotron radiation beamlines or automated systems used in industry.Attention should be paid to an eventual instability of the layers over the duration of the data collect

33、ion, which would cause a reduction in the accuracy of the measurement results. Since XRR, performed at a single wavelength, does not provide chemical information about the layers, attention should be paid to possible contamination or reactions at the specimen surface. The accuracy of results for the

34、 outmost layer is strongly influenced by any changes at the surface.2 Terms, definitions, symbols and abbreviated terms2.1 Terms and definitions2.1.1incidence angleangle betwen the incident beam and the specimen surface2.1.2critical anglecangle between the incident beam and the specimen surface, bel

35、ow which there is total external reflection of X-rays, and above which the X-ray beam penetrates below the surface of the specimenNote 1 to entry: The critical angle for a given specimen material or structure can be found by using simulation software, or approximated from the formula c 2 where 1 is

36、the real part of the complex X-ray refractive index n = 1 i.2.1.3specimen lengthdimension of the specimen in the plane of the incident and reflected X-ray beams and in the plane of the specimen2.1.4specimen widthdimension of the specimen perpendicular to the plane of the incident and reflected X-ray

37、 beams and in the plane of the specimenINTERNATIONAL STANDARD ISO 16413:2013(E) ISO 2013 All rights reserved 1BS ISO 16413:2013ISO 16413:2013(E)2.1.5specimen heightZdimension (thickness) of the specimen perpendicular to the plane of the specimen2.1.6layer thicknessthickness of an individual layer on

38、 the substrate2.1.7beam footprintarea on the specimen irradiated by the X-ray2.1.8beam spill-offeffect of grazing incidence that involves the reduction of the measured reflected intensity when part of the incident beam is not intercepted by the specimen, so that the part spills off the specimen2.1.9

39、instrument functionanalytical function describing the effects of instrument and resolution on the observed scattered X-ray intensity2.1.10reciprocal spacerepresentation of the physical specimen and X-rays where the distance plotted is proportional to the inverse of real-space distances, and angles c

40、orrespond to real-space angles2.1.11wave vectorkvector in reciprocal space describing the incident or scattered X-ray beams2.1.12scattering vectorqvector in reciprocal space giving the difference between the scattered and incident wave vectors2.1.13dispersion planeplane containing the source, detect

41、or, incident and specularly reflected X-ray beams2.1.14specular X-ray reflectivityreflected X-ray signal detected at an angle with the specimen surface as the incident X-ray beam with the specimen surface: 2/2 = Note 1 to entry: The detected, scattered X-ray intensity is measured as a function of ei

42、ther or 2 or qz(usually presented against qzor ).2.1.15diffuse X-ray reflectivityX-ray scatter arising from the imperfection of the specimen2.1.16fringeone of the repeating maxima in reflectometry data which arise from interference of the X-ray wavesNote 1 to entry: Fringe periods are related to the

43、 thickness of a layer (or layers) of contrasting electron density. Multiple layers give rise to series of superposed interfering fringes.2 ISO 2013 All rights reservedBS ISO 16413:2013ISO 16413:2013(E)2.1.17fringe contrastqualitative description of the height of a fringe between its minimum and its

44、maximumNote 1 to entry: The greater the difference between minimum and maximum, the greater the contrast is said to be.2.1.18electron densityeelectrons per unit volumeNote 1 to entry: XRR typically measures electron density in electrons per nm3or per 3.Note 2 to entry: This can be calculated from ma

45、ss density.2.1.19mass densitycommon density (mass per unit volume)Note 1 to entry: It is measured in kg m3(or sometimes in g cm3).2.1.20absorption lengthLabsdistance over which the transmitted intensity falls to 1/e of the incident intensity2.1.212theta2angle of the detected X-ray beam with respect

46、to the incident X-ray beam direction2.1.22omegaangle between the incident X-ray beam and the specimen surface2.1.23phiangle of rotation about the normal to the nominal surface of the specimen2.1.24chiangle of tilt of specimen about an axis in the plane of the specimen and in the plane of the inciden

47、t X-ray beam, X-ray source and detector2.1.25X, Y, Z coordinate systemorthogonal coordinate system in which X is the direction in the plane of the specimen, parallel to the incident beam when = 0; Y is the direction in the plane of the specimen, perpendicular to the incident beam when = 0; and Z is

48、the direction normal to the plane of the specimen ISO 2013 All rights reserved 3BS ISO 16413:2013ISO 16413:2013(E)2.2 Symbols and abbreviated terms2 2Theta, the angle of the detected X-ray beam with respect to the incident X-ray beam Omega, the angle between the incident X-ray beam and the specimen

49、surface Phi, the angle of rotation about the normal to the nominal surface of the specimen Chi, the angle of tilt of specimen about an axis in the plane of the specimen and in the plane of the incident X-ray beam, X-ray source and detectorcCritical angle Wavelength of the incident X-ray beam Mass densityeElectron densityk Wave vectorq Scattering vectorqzScalar magnitude of the component of the scattering vector in reciprocal space normal to the specimen surface (corrected or uncorrected for refractio