ASTM_F_1810_-_97.pdf

Designation:F 1810 97Standard Test Method forCounting Preferentially Etched or Decorated SurfaceDefects in Silicon Wafers1This standard is issued under the fixed designation F 1810;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 test method describes the technique to count thedensity of surface defects in silicon wafers by microscopicanalysis.NOTE1Practical use of a defect counting method requires an assump-tion be made that defects are randomly distributed on the surface.If thisassumption is not met,the accuracy and precision of this test method willbe diminished.1.2 Application of this test method is limited to specimensthat have discrete,identifiable artifacts on the surface of thesilicon sample.Typical samples have been preferentiallyetched according to Guide F 1809 or epitaxially deposited,forming defects in a silicon layer structure.1.3 Wafer thickness and diameter for this test method islimited only by the range of microscope stage motions avail-able.1.4 This test method is applicable to silicon wafers withdefect density between 0.01 and 10 000 defects per cm2.NOTE2The commercially significant defect density range is between0.01 to 10 defects per cm2,but this test method extends to higher defectlevels due and improved statistical sampling obtained with higher counts.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:F 1241 Terminology of Silicon Technology2F 1725 Practice for Analysis of Crystallographic Perfectionof Silicon Ingots2F 1726 Practice for Analysis of Crystallographic Perfectionof Silicon Wafers2F 1727 Practice for Detection of Oxidation Induced Defectsin Polished Silicon Wafers2F 1809 Guide for Selection and Use of Etching Solutions toDelineate Structural Defects in Silicon23.Terminology3.1 Definitions of terms related to silicon technology arefound in Terminology F 1241.4.Summary of Test Method4.1 Selected and prepared samples for this test used PracticeF 1725,F 1726 or F 1727.The defect to be analyzed is exposedusing a specific etching solution suggested in Guide F 1809.4.2 Align the wafer on a microscope stage,inspect accord-ing to predefined inspection pattern and count specific defectsdistinguished by shape or size.4.3 The basic inspection pattern is a single diametric scanthough the center point of the wafer.4.4 The starting and ending points of the scan pattern are 5mm from the edges of the wafer.Fig.1 represents thecharacteristics of the pattern.4.5 The complete inspection pattern of this test method isbased upon the combination of four separate scans acrossdifferent diameters.5.Significance and Use5.1 Defects on or in silicon wafers may adversely affectdevice performance and yield.5.2 Crystal defect analysis is a useful technique in trouble-shooting device process problems.The type,location,anddensity of defects counted by this test method may be relatedto the crystal growth process,surface preparation,contamina-tion,or thermal history of the wafer.5.3 This test method is suitable for acceptance testing whenused with referenced standards.6.Interferences6.1 Improper identification of defects is possible during thecounting process.6.1.1 Contamination not removed by cleaning procedures ordeposited following cleaning,may become visible after pref-erential etching.6.1.2 Insufficient agitation during the preferential etchingprocess may cause artifacts that may be mistaken as crystallo-graphic defects.6.2 The accuracy of the defect density calculation is directlyaffected by calibration of the area of the microscope field ofview.6.3 The defect density determined by this test methodrequires an assumption be made that defects are randomly1This test method is under the jurisdiction of ASTM Committee F-1 onElectronics and is the direct responsibility of Subcommittee F01.06 on SiliconMaterials and Process Control.Current edition approved June 10,1997.Published August 1997.2Annual Book of ASTM Standards,Vol 10.05.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMdistributed on the surface.Nonuniform patterns of defects alterthe defect density measurement by their size and location.6.4 Multiple scan patterns intersect at the center of thewafer.If a defect is found at this single,common point,it iscounted more than once and shall alter the accuracy.7.Apparatus7.1 Nonmetallic Vacuum Pickup Tool,of suitable materialsuch as quartz or TFE-fluorocarbon.The pickup tool shall b