ASTM_E_1438_-_11.pdf

Designation:E143811Standard 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 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 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 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 limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E673 Terminology Relating to Surface Analysis(Withdrawn2012)33.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 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 incidence 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.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 analyticaltechnique.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).4This guide,describes a method 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 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 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).Therefore,this measure of interface width may have norelation to similar measures made with other methods.However,this does not diminish its use as a check on proper orconsistent instrument performance,or both.1This 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 2011.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 standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4The boldface numbers given in parentheses refer to a list of references at theend of this guide.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 This guide can be used for both elemental and moleculardepth profiles,provided that the materials have constant sputterrates throughout the depth of the overlayer,and minimalinterlayer mixing is occurring.For more detailed informationregarding measurements of interface widths during organicdepth profiling,please see Mahoney(8).6.Apparatus6.1 The procedure described in this guide can be