ASTM_F_996_-_11.pdf

Designation:F99611Standard Test Method forSeparating an Ionizing Radiation-Induced MOSFETThreshold Voltage Shift Into Components Due to OxideTrapped Holes and Interface States Using the SubthresholdCurrentVoltage Characteristics1This standard is issued under the fixed designation F996;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the use of the subthresholdcharge separation technique for analysis of ionizing radiationdegradationofagatedielectricinametal-oxide-semiconductor-field-effect transistor(MOSFET)and an isola-tion dielectric in a parasitic MOSFET.2,3,4The subthresholdtechnique is used to separate the ionizing radiation-inducedinversion voltage shift,VINVinto voltage shifts due to oxidetrapped charge,Votand interface traps,Vit.This techniqueuses the pre-and post-irradiation drain to source current versusgate voltage characteristics in the MOSFET subthresholdregion.1.2 Procedures are given for measuring the MOSFET sub-threshold current-voltage characteristics and for the calculationof results.1.3 The application of this test method requires the MOS-FET to have a substrate(body)contact.1.4 Both pre-and post-irradiation MOSFET subthresholdsource or drain curves must follow an exponential dependenceon gate voltage for a minimum of two decades of current.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 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:5E666 Practice for Calculating Absorbed Dose From Gammaor X RadiationE668 Practice for Application of Thermoluminescence-Dosimetry(TLD)Systems for Determining AbsorbedDose in Radiation-Hardness Testing of Electronic DevicesE1249 Practice for Minimizing Dosimetry Errors in Radia-tion Hardness Testing of Silicon Electronic Devices UsingCo-60 SourcesE1894 Guide for Selecting Dosimetry Systems for Applica-tion in Pulsed X-Ray Sources3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 anneal conditionsthe current and/or voltage bias andtemperature of the MOSFET in the time period betweenirradiation and measurement.3.1.2 doping concentration n-or p-type doping,is theconcentration of the dopant in the MOSFET channel regionadjacent to the oxide/silicon interface.3.1.3 Fermi levelthis value describes the top of thecollection of electron energy levels at absolute zero tempera-ture.3.1.4 intrinsic Fermi levelthe energy level that the Fermilevel has in the absence of any doping.3.1.5 inversion current,IINVthe MOSFET channel currentat a gate-source voltage equal to the inversion voltage.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.11 on Nuclear andSpace Radiation Effects.Current edition approved Jan.1,2011.Published January 2011.Originallyapproved in 1991.Last previous edition approved in 2010 as F996 10.DOI:10.1520/F0996-11.2McWhorter,P.J.and P.S.Winokur,“Simple Technique for Separating theEffects of Interface Traps and Trapped Oxide Charge in MOS Transistors,”AppliedPhysics Letters,Vol 48,1986,pp.133135.3DNA-TR-89-157,Subthreshold Technique for Fixed and Interface TrappedCharge Separation in Irradiated MOSFETs,available from National TechnicalInformation Service,5285 Port Royal Rd.,Springfield,VA 22161.4Saks,N.S.,and Anacona,M.G.,“Generation of Interface States by IonizingRadiation at 80K Measured by Charge Pumping and Subthreshold SlopeTechniques,”IEEE Transactions on Nuclear Science,Vol NS34,No.6,1987,pp.13481354.5For 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 3.1.6 inversion voltage,VINVthe gate-source voltage cor-responding to a surface potential of 2B.3.1.7 irradiation biasesthe biases on the gate,drain,source,and substrate of the MOSFET during irradiation.3.1.8 midgap current,IMGthe MOSFET channel current ata gate-source voltage equal to the midgap voltage.3.1.9 midgap voltage,VMGthe gate-source voltage corre-sponding to a surface potential of B.3.1.10 oxide thickness,toxthe thickness of the oxide of theMOSFET under test.3.1.11 potential,Bthe potential difference between theFermi level and the intrinsic Fermi level.3.1.12 subthreshold swingthe change in t