ASTM_F_1259M_-_96_2003.pdf

Designation:F 1259M 96(Reapproved 2003)METRICStandard Guide forDesign of Flat,Straight-Line Test Structures for DetectingMetallization Open-Circuit or Resistance-Increase FailureDue to Electromigration Metric1This standard is issued under the fixed designation F 1259M;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide covers recommended design features for teststructures used in accelerated stress tests,as described in TestMethod F 1260M,to characterize the failure distribution ofinterconnect metallizations that fail due to electromigration.1.2 This guide is restricted to structures with a straight testline on a flat surface that are used to detect failures due to anopen-circuit or a percent-increase in resistance of the test line.1.3 This guide is not intended for testing metal lines whosewidths are approximately equal to or less than the estimatedmean size of the metal grains in the metallization line.1.4 This guide is not intended for test structures used todetect random defects in a metallization line.1.5 Metallizations tested and characterized are those that areused in microelectronic circuits and devices.2.Referenced Documents2.1 ASTM Standards:F 1260M Test Method for Estimating ElectromigrationMedian-Time-To-Failure and Sigma of Integrated CircuitMetallizations Metric2F 1261M Test Method for Determining the Average Elec-trical Width of a Straight,Thin-Film Metal Line Metric3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 test chipan area on a semiconductor wafer contain-ing one or more test structures having a specified or impliedpurpose.3.1.2 test structurea passive metallization structure,withterminals to permit electrical access that is fabricated on asemiconductor wafer by the normal procedures used to manu-facture microelectronic integrated devices.3.1.3 metallizationthe thin-film metallic conductor thatserves as the primary conductor path in electrical interconnectsof microelectronic integrated circuits.4.Significance and Use4.1 This guide is intended for the design of test structuresused in measuring the median-time-to-failure and sigma(seeTest Method F 1260M)of metallizations fabricated in waysthat are of interest to the parties to the test.4.2 This guide is intended to provide design features thatfacilitate accurate test-line resistance measurements used inestimating metallization temperature.The design features arealso intended to promote temperature uniformity along the testline and a minimum temperature gradient at the ends of the testline when significant joule heating is produced during theaccelerated stress test.5.Design Features5.1 The test structure shall have at least four terminals:twoto conduct current and two to measure the voltage.The basicfeatures are illustrated in Fig.1.5.1.1 The metallization to be characterized by the teststructure shall be in the form of a straight test line of width w,where w shall be larger than the estimated mean size of themetal grains in the metallization of the test line.NOTE1The median-time-to-failure,t50,(see Test Method F 1260M)will be a monotonically increasing function of line width w,when w islarger than the mean size of the metal grains in the test line.NOTE2If the mean size of the metal grains in the test line is largerthan the line width,there is an increasing probability,for decreasing linewidth,that failure will occur in the wider end segment of the structure,rather in the test line,for decreasing line width.This is because both t50and sigma increase with decreasing line width in this regime.5.1.2 The length of the test line shall be 800 m.Adjacent-running lines may be included in the design to simulateactual-circuit layout,or to serve as monitor lines to detectelectromigration-induced metal extrusions from the test line.NOTE3The specification on the length of the test line is two-fold:tofacilitate comparison of t50values(see Test Method F 1260M),because t501This guide is under the jurisdiction of ASTM Committee F01 on Electronicsand is the direct responsibility of Subcommittee F01.11 on Quality and HardnessAssurance.Current edition approved June 10,1996.Published August 1996.Originallypublished as F 1259 89.Last previous edition F 1259 89.2Annual Book of ASTM Standards,Vol 10.04.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.decreases gradually with increasing line length,and to avoid a relativelynonuniform temperature along much shorter test lines when the current-density stress levels are great enough to produce significant jouleheating.3NOTE4All dimensions specified here and elsewhere are designeddimensions.It is expected that the actual dimensions will differ somewhatdue to processing.5.1.3 E