ASTM_F_1238_-_95_2011.pdf

Designation:F123895(Reapproved 2011)Standard Specification forRefractory Silicide Sputtering Targets for MicroelectronicApplications1This standard is issued under the fixed designation F1238;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 specification covers sputtering targets fabricatedfrom metallic silicides(molybdenum silicide,tantalum silicide,titanium silicide,and tungsten silicide).These targets arereferred to as refractory silicide targets,and are intended foruse in microelectronic applications.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 raw material lotpowder mix lot from which anumber of targets is fabricated.2.1.2 relative densityactual target density related to theo-retical density,(see 3.1.3),stated as percent.2.1.3 theoretical densitycalculated density for given com-position as described in 5.3.3.Ordering Information3.1 Orders for these targets shall include the following:3.1.1 Type and ratio(see 4.1 and 4.2),3.1.2 Whether low alpha grade is required,(see 4.4),3.1.3 Minimum relative density,if other than 90%,(see5.1),3.1.4 Configuration,(see 6.1),3.1.5 Whether certification is required,(see 10.1).4.Chemical Composition4.1 TypeTargets shall be classified by the following majorconstituents:4.1.1 Molybdenum silicide,(Mo/Si),4.1.2 Tantalum silicide,(Ta/Si),4.1.3 Titanium silicide,(Ti/Si),and4.1.4 Tungsten silicide,(W/Si).4.2 RatioTarget composition shall be stated as the atomicratio of silicon to metal,such as Ta/Si 2.5.Ratio tolerance shallbe 6 0.1.Therefore,the acceptable range for a 2.5 target wouldbe 2.4 to 2.6.NOTE1Silicon content may be calculated from the following formula:Silicon,%5Ratio3ARatio3A!1B3100where:A=atomic weight of silicon,andB=atomic weight of metal,(see Table 12-4).4.3 ImpuritiesMaximum impurity levels shall conform tothe requirements prescribed in Table 2.4.4 Low Alpha GradeWhen low alpha grade targets areordered they shall contain a maximum impurity level ofuranium and thorium as agreed upon by the supplier and thepurchaser.The method of analysis for these elements shall alsobe agreed upon.NOTE2An alternative method for defining low alpha grade targets isto specify an alpha-emission rate.Specific methodology and emission rateshall be agreed upon by supplier and purchaser.4.5 When required by purchaser,supplier will provide a 25g sample of material that is representative of the total produc-tion process for the particular raw material lot,(see Section 8).5.Physical Properties5.1 Minimum relative density shall be 90%.Other relativedensities may be specified by the purchaser.5.2 Actual target density shall be determined byArchimedesprinciple or other acceptable techniques.1This specification is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.17 on SputterMetallization.Current edition approved June 1,2011.Published June 2011.Originallypublished as F1238 89.Last previous edition approved in 2003 as F1238 95(2003).DOI:10.1520/F1238-95R11.2Molybdenum disilicide and WSi2(equilibrim tetragonal phase)densities werecomputed from crystal lattice parameters tabulated in“Crystal Data-DeterminativeTables,Third Edition,”Vol 2,U.S.Department of Commerce,National Bureau ofStandards and the Joint Committee on Powder Diffraction Standards,1973,andJCPDS Data File Number 11-195.Tantalum disilicide(hexagonal)and a-TiSi2(orthorhombic)data are from Einspruch,N.G.and Larrabee,G.B.,VLSIElectronics Microstructure Science,Vol 6,Table A.1,Academic Press,NY,NY,1983.3Binary Alloy Phase Diagrams,Vol 2,ASM,Metals Park,OH.4Einspruch,N.G.,and Larrabee,G.B.,VLSI Electronics MicrostructureScience,Vol 6,Table A.1,Academic Press,NY,NY,1983.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 Theoretical density shall be calculated from the follow-ing formula:Theoretical density5C1Ratio22!3AC/D1Ratio22!3A/Ewhere:A=atomic weight of silicon,C=molecular weight of metal silicide,(MoSi2,etc),D=density of metal silicide,andE=density of silicon,(see Table 1).6.Dimensions6.1 Each target shall conform to an appropriate engineeringdrawing.7.Workmanship,Finish,and Appearance7.1 There shall be no radial cracks.7.2 There shall be no other cracks or chips on the sputteringsurface.7.3 Examination for cracks and chips shall be made by theunaided eye under good lighting conditions.8.Sampling8.1 Analyses for ratio,(see 4.2)and for impurities,(see 4.3and 4.4)shall be performed on a sample that is representativeof the finished product.9.Analytical Methods9.1 Do analysis for ratio,(see 4.2)by a technique that