ASTM_F_1438_-_93_2012.pdf

Designation:F143893(Reapproved 2012)Standard Test Method forDetermination of Surface Roughness by ScanningTunneling Microscopy for Gas Distribution SystemComponents1This standard is issued under the fixed designation F1438;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.INTRODUCTIONSemiconductor clean rooms are serviced by high-purity gas distribution systems.This test methodpresents a procedure that may be applied for the evaluation of one or more components considered foruse in such systems.1.Scope1.1 The purpose of this test method is to define a method foranalyzing the surface texture of the above-mentioned compo-nents using a scanning tunneling microscope(STM).STM is anoncontact method of surface profiling that can measurethree-dimensional surface features in the nanometer size range,which can then be used to represent the surface texture or toprovide figures of merit.Application of this test method,wheresurface texture is used as a selection criterion,is expected toyield comparable data among different components tested.1.2 Limitations:1.2.1 This test method is limited to characterization ofstainless steel surfaces that are smoother than Ra=0.25 m,asdetermined by a contact-stylus profilometer and defined byANSI B46.1.The magnifications and height scales used in thistest method were chosen with this smoothness in mind.1.2.2 Intentional etching or conductive coating of the sur-face are considered modifications of the gas-wetted surface andare not covered by this test method.1.2.3 This test method does not cover steels that have anoxide layer too thick to permit tunneling under the testconditions outlined in 11.3.1.3 This technique is written with the assumption that theSTM operator understands the use of the instrument,itsgoverning principles,and any artifacts that can arise.Discus-sion of these points is beyond the scope of this test method.1.4 The values stated in SI units are to be regarded as thestandard.1.5 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:E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method22.2 ANSI Standard:ANSI B.46.1-85,“Surface Texture(Surface Roughness,Waviness,and Lay),”ANSI/ASME,198533.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 artifactany contribution to an image from other thantrue surface morphology.This could include such examples asvibration,electronic noise,thermal drift,or tip imperfections.3.1.2 center line(graphical center line)line parallel to thedirection of profile measurement,such that the sum of the areascontained between it and the profile contained on either sideare equal(see Calculation Section).3.1.3 cutoff length(lc)for profiles in this context,thesampling length,that is,the length of a single scan,innanometers(see Calculation Section).3.1.4 current in this context,the tunneling current(ex-pressed in nanoamperes)that flows in either direction betweenthe tip and surface,under the conditions specified.1This test method is under the jurisdiction of ASTM Committee F01 onElectronicsand is the direct responsibility of Subcommittee F01.10 on Contamina-tion Control.Current edition approved July 1,2012.Published August 2012.Originallyapproved in 1993.Last previous edition approved in 2005 as F143893(2005).DOI:10.1520/F1438-93R12.2For 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.3Available from American National Standards Institute,13th Floor,11 W.42ndSt.,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.5 feature heightdatum(height in the z-direction)ofany point in the scan area,relative to the lowest point in thescan area,as derived from tunneling current during tip raster-ing.3.1.6 filterprocess of modification of surface data forpurposes of numerical analysis or data presentation.Examplesinclude high or low pass filters and plane-fitting.3.1.7 gold ruled gratinggold surface having uniformlyspaced grooves of known depth and separation;used formicrometer scale x-y calibration.3.1.8 illuminated surfacethree-dimensional image repre-sentation that simulates a reflective surface illuminatedobliquely or from overhead.3.1.9imagesurface topography represented by plottingfeature height as a function of tip position.The feature heightdata