ASTM_F_1725_-_97.pdf

Designation:F 1725 97Standard Guide forAnalysis of Crystallographic Perfection of Silicon Ingots1This standard is issued under the fixed designation F 1725;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 practice covers the analysis of the crystallographicperfection in silicon ingots.The steps described are samplepreparation,etching solution selection and use,defect identi-fication,and defect counting.1.2 This practice is suitable for use if evaluating silicongrown in either 111 or 100 direction and doped either p orn type with resistivity greater than 0.005 Vcm.1.3 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:D 5127Guide for Electronic Grade Water2F 26 Test Method for Determining the Orientation of aSemiconductor Single Crystal3F 523 Practice for Unaided Visual Inspection of PolishedSilicon Wafers3F 1241 Terminology of Silicon Technology3F 1809 Guide for Selection and Use of Etching Solutions toDelineate Structural Defects in Silicon3F 1810 Test Method for Counting Preferentially Etched orDecorated Surface Defects in Silicon Wafers22.2SEMI Specifications:SEMI C-1 Specification for Reagents4.3.Terminology3.1 Defect-related terminology may be found in Terminol-ogy F 1241.4.Summary of Practice4.1 The end portion of the silicon crystal,which solidifiedlast,may contain dislocations or other defects such as slip.Theportion containing the defects is removed by sawing thecrystal.A specimen wafer from the end of the remaining ingotis obtained with a second cut.4.2 This wafer is mechanically lapped,chemically polished,and then etched in a preferential defect etching solution.4.3 The etched surface is examined under bright lightillumination and examined microscopically to count and clas-sify the imperfections highlighted by the preferential defectetching solution.5.Significance and Use5.1 The use of silicon wafers in many semiconductordevices requires a consistent atomic lattice structure.Crystaldefects disturb local lattice energy conditions that are the basisfor semiconductor behavior.These defects have distinct effectson essential semiconductor device-manufacturing processessuch as alloying and diffusion.5.2 This practice along with the referenced standards maybe used for process control,research and development,andmaterials acceptance purposes.6.Apparatus6.1 Slicing Equipment,suitable for removing wafers ofvaried thickness from ingots.6.2 Lapping or Grinding Equipment(optional),suitable forremoving saw damage.6.3 Laboratory Equipment,suitable for use with hydrofluo-ric acid(fluorocarbon,polyethylene,or prolypropylene bea-kers,graduates,pipets,and nonmetallic wafer pickup tools).6.4 Acid Sink,in a fume hood and facilities for disposing ofacids and their vapors.6.5 Personnel Safety Equipment,for handling acids,such asgloves,safety glasses,face shield,and gown.7.Reagents and Materials7.1 All chemicals for which such specifications exist shallconform to SEMI specifications C1.7.2 Reference to water shall be understood to mean eitherdistilled water or deionized water,meeting the requirements ofType I water as defined by Guide D 5127.7.3 A variety of etching solutions exist.They have beenfound to produce satisfactory results as illustrated in Table 17.4 An aqueous,nonionic surfactant detergent solution.8.Hazards8.1 The chemicals used in polishing etches are potentiallyharmful and must be handled in a chemical exhaust fume hood,with the utmost care.1This guide is under the jurisdiction ofASTM Committee F-1 on Electronics andis the direct responsibility of Subcommittee F01.06 on Silicon Materials and ProcessControl.Current edition approved June 10,1997.Published August 1997.2Annual Book of ASTM Standards,Vol 11.01.3Annual Book of ASTM Standards,Vol 10.05.4Available from Semiconductor Equipment and Materials International,805 EMiddlefield Rd.,Mountain View,CA 94043.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM8.2 Hydrofluoric acid solutions are particularly hazardousand the specific preventive measures must be strictly observed.8.3 Safety or protective gear should be worn while handlingthese acid solutions or their components.Safety requirementsvary,but the essentials are:plastic gloves,safety glasses,faceshield,acid gown,and shoe covers.9.Procedure9.1 Sample selectionTake the sample for evaluation fromthe crystal close to the discarded crystal portion found at thelast of the solidified crys