ASTM_F_617_-_00.pdf

Designation:F 617 00Standard Test Method forMeasuring MOSFET Linear Threshold Voltage1This standard is issued under the fixed designation F 617;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 covers the measurement of MOSFET(see Note 1)linear threshold voltage under very low sweep rateor d-c conditions.It is a d-c conductance method applicable inthe linear region of MOSFET operation where a drain voltageVDof approximately 0.1 V is typical.NOTE1MOS is an acronym for metal-oxide semiconductor;FET isan acronym for field-effect transistor.1.2 This test method is applicable to both enhancement-mode and depletion-mode MOSFETs,and for both silicon-on-insulator(SOI)and bulk-silicon MOSFETs.The test methodspecifies positive voltage and current conventions specificallyapplicable to n-channel MOSFETs.The substitution of nega-tive voltage and negative current make the test method directlyapplicable to p-channel MOSFETs.1.3 The values stated in International System of Units(SI)are to be regarded as standard.No other units of measurementare included in this test method.1.4This 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.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 drain-leakage currentof a MOSFET,the d-c currentfrom the drain terminal when the gate voltage with respect tothe threshold voltage is such that the MOSFET is in the OFFstate.2.1.2 threshold voltageof a MOSFET,for operation in thelinear region,the gate-to-source voltage at which the draincurrent is reduced to the leakage current.3.Summary of Test Method3.1 The drain-source current of the MOSFET under test ismeasured at several values of gate voltage for a fixed drain-source voltage.A linear plot is made of the drain current as afunction of gate voltage.The maximum tangent to the resultingcurve is extrapolated to the gate-voltage axis or to the voltageindependent line representing the drain-leakage current.Thisintercept is the threshold voltage for the drain-source voltageand temperature conditions of the test.3.2 Before this test method can be implemented,test con-ditions appropriate for the MOSFET to be measured must beselected and agreed upon by the parties to the test.Conditionswill vary from one MOSFET type to another,and are deter-mined in part by the intended application.The following itemsare not specified by this test method,and shall be agreed uponbetween the parties to the test:3.2.1 Reference temperature to which the measured thresh-old voltages shall be normalized.3.2.2 Permissible range of ambient temperature withinwhich the measurement is to be conducted.The referencetemperature shall be within this range.NOTE2The temperature sensitivity of the threshold voltage may be aslarge as 5 mV/C,or more.The reproducibility of the measurements willbe degraded accordingly,unless the values of the threshold voltage arenormalized to a common reference temperature.To reduce the effect thatuncertainties in the temperature sensitivity of the test devices will have onthe reproducibility,no more than an appropriately small range of testtemperatures should be allowed.3.2.3 Drain voltage VDat which the measurement is to bemade.3.2.4 Maximum drain current,IDM,maximum gate voltage,VGM,and gate voltage steps,DVG,over which the measurementis to be made.Values for IDM,VGM,and D VGshall be selectedto permit taking enough data points to define adequately thedrain-current,gate-voltage characteristic curve in the region ofthe inflection point,namely,where the tangent to the curve hasthe largest slope(maximum tangent).The value selected forDVGshall be one of the following:0.02,0.05,0.10,0.20,or0.50 V.The recommended procedure for selecting values forIDM,VGM,and DVGis provided in the Appendix.4.Significance and Use4.1 The threshold voltage is a basic MOSFET parameterthat must be determined for the design and application ofdiscrete MOSFETs and MOS(see Note 1)integrated circuits.Threshold voltage is utilized in circuit design to specify the1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.11 on Quality andHardness Assurance.Current edition approved June 10,2000.Published October 2000.Originallypublished as F 617 79.Last previous edition F 617M 95.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.turn-on voltage of MOSFETs,and thereby determine perfor-mance attributes such as speed,power,noise margin,etc.,ofdigital and anal