ASTM_F_1894_-_98_2011.pdf

Designation:F189498(Reapproved 2011)Test Method forQuantifying Tungsten Silicide Semiconductor Process Filmsfor Composition and Thickness1This standard is issued under the fixed designation F1894;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 test method covers the quantitative determinationof tungsten and silicon concentrations in tungsten/silicon(WSix)semiconductor process films using Rutherford Back-scattering Spectrometry(RBS).2(1)This test method alsocovers the detection and quantification of impurities in themass range from phosphorus (31 atomic mass units(amu)toantimony(122 amu).1.2 This test method can be used for tungsten silicide filmsprepared by any deposition or annealing processes,or both.The film must be a uniform film with an areal coverage greaterthan the incident ion beam(;2.5 mm).1.3 This test method accurately measures the following filmproperties:silicon/tungsten ratio and variations with depth,tungsten depth profile throughout film,WSixfilm thickness,argon concentrations(if present),presence of oxide on surfaceof WSixfilms,and transition metal impurities to detectionlimits of 11014atoms/cm2.1.4 This test method can detect absolute differences insilicon and tungsten concentrations of 63 and 61 atomicpercent,respectively,measured from different samples inseparate analyses.Relative variations in the tungsten concen-tration in depth can be detected to 60.2 atomic percent with adepth resolution of 670.1.5 This test method supports and assists in qualifying WSixfilms by electrical resistivity techniques.1.6 This test method can be performed for WSixfilmsdeposited on conducting or insulating substrates.1.7 This test method is useful forWSixfilms between 20 and400 nm with an areal coverage of greater than 1 by 1 mm2.1.8 This test method is non-destructive to the film to theextent of sputtering.1.9 A statistical process control(SPC)of WSixfilms hasbeen monitored since 1993 with reproducibility to 64%.1.10 This test method produces accurate film thicknesses bymodeling the film density of theWSixfilm asWSi2(hexagonal)plus excess elemental Si2.The measured film thickness is alower limit to the actual film thickness with an accuracy lessthan 10%compared to SEM cross-section measurements(see13.4).1.11 This test method can be used to analyze films on wholewafers up to 300 mm without breaking the wafers.The sitesthat can be analyzed may be restricted to concentric rings nearthe wafer edges for 200-mm and 300-mm wafers,dependingon system capabilities.1.12 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.13 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.The reader isreferenced to Section 8 of this test method for references tosome of the regulatory,radiation,and safety considerationsinvolved with accelerator operation.2.Referenced Documents2.1 Terminology used in this document is consistent withterms and definitions as used in the Compilation of ASTMStandard Definitions,8thed ASTM,1994,Philadelphia PA,USA,specifically for terms taken from the following ASTMstandards:2.2 ASTM Standards:3E1351This test method is under the jurisdiction of Committee F01 on Electronics,andis the direct responsibility of Subcommittee F01.17 on Sputter Metallization.Current edition approved June 1,2011.Published June 2011.Originallyapproved in 1998.Last previous edition approved in 2003 as F189498(03).DOI:10.1520/F1894-98R11.2The boldface numbers in parentheses refer to a list of references at the end ofthe text.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 E673 Terminology Relating to Surface Analysis(Withdrawn2012)4E1241 Guide for Conducting Early Life-Stage Toxicity Testswith Fishes3.Terminology3.1 Numerous terms specific to RBS and ion stopping insolids can be found in the following references(1,2)2.3.2 Definitions of Terms Specific to This Standard:3.2.1 WSixa tungsten silicide film characterized by asilicon/tungsten atomic ratio 2.00.3.2.2 incident ionsHe+or He+ions with energy in therange of 2.25 to 2.30 MeV delivered to a sample surface froman appropriate ion source and accelerator system.3.2.3 backscattered ionsHelium particles(charged or neu-tral)recoiling from atoms in a