ASTM_F_1711_-_96_2008.pdf

Designation:F171196(Reapproved 2008)Standard Practice forMeasuring Sheet Resistance of Thin Film Conductors forFlat Panel Display Manufacturing Using a Four-Point ProbeMethod1This standard is issued under the fixed designation F1711;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 practice describes methods for measuring the sheetelectrical resistance of sputtered thin conductive films depos-ited on large insulating substrates,used in making flat panelinformation displays.It is assumed that the thickness of theconductive thin film is much thinner than the spacing of thecontact probes used to measure the sheet resistance.1.2 This standard is intended to be used with Test MethodF390.1.3 Sheet resistivity in the range 0.5 to 5000 ohms persquare may be measured by this practice.The sheet resistanceis assumed uniform in the area being probed.1.4 This practice is applicable to flat surfaces only.1.5 Probe pin spacings of 1.5 mm to 5.0 mm,inclusive(0.059 to 0.197 in inclusive)are covered by this practice.1.6 The method in this practice is potentially destructive tothe thin film in the immediate area in which the measurementis made.Areas tested should thus be characteristic of thefunctional part of the substrate,but should be remote fromcritical active regions.The method is suitable for characteriz-ing dummy test substrates processed at the same time assubstrates of interest.1.7 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.8 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:2F390 Test Method for Sheet Resistance of Thin MetallicFilms With a Collinear Four-Probe Array3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice see TestMethod F390.4.Summary of Practice4.1 This practice describes the preferred means of applyingTest Method F390 to measure the electrical sheet resistance ofthin films on very large flat substrates.An array of four pointedprobes is placed in contact with the film of interest.Ameasuredelectrical current is passed between two of the probes,and theelectrical potential difference between the remaining twoprobes is determined.The sheet resistance is calculated fromthe measured current and potential values using correctionfactors associated with the probe geometry and the probesdistance from the test specimens boundaries.4.2 The method of F390 is extended to cover staggeredin-line and square probe arrays.In all the designs,however,theprobe spacings are nominally equal.4.3 This practice includes a special electrical test for veri-fying the proper functioning of the potential measuring instru-ment(voltmeter),directions for making and using sheet resis-tance reference films,an estimation of measurement errorcaused by probe wobble in the probe supporting fixture,and aprotocol for reporting film uniformity.4.4 Two appendices indicate the computation methods em-ployed in deriving numerical relationships and correctionfactors employed in this practice,and in Test Method F390.1This practice is under the jurisdiction of ASTM Committee F01 on Electronicsand is the direct responsibility of Subcommittee F01.17 on Sputter Metallization.Current edition approved June 15,2008.Published July 2008.Originallyapproved in 1996.Last previous edition approved in 2002 as F1711 96(2002).DOI:10.1520/F1711-96R08.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Significance and Use5.1 Applying Test Method F390 to large flat panel substratespresents a number of serious difficulties not anticipated in thedevelopment of that standard.The following problems areencountered.5.1.1 The four-point probe method may be destructive to thethin film being measured.Sampling should therefore be takenclose to an edge or corner of the plate,where the film isexpendable.Special geometrical correction factors are thenrequired to derive the true sheet resistance.5.1.2 Test Method F390 is limited to a conventional col-linear probe arrangement,but a staggered collinear and squarearrays are useful in particular circumstances.Correction factorsare needed to account for nonconventional probe arrange-ments.5.1.3 Test Method F390 anticipates a