ASTM_F_978_-_90_1996e1.pdf

Designation:F 978 90(Reapproved 1996)e1Standard Test Method forCharacterizing Semiconductor Deep Levels by TransientCapacitance Techniques1This standard is issued under the fixed designation F 978;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.e1NOTEKeywords were added editorially in January 1996.1.Scope1.1 This test method covers three procedures for determin-ing the density,activation energy,and prefactor of the expo-nential expression for the emission rate of deep-level defectcenters in semiconductor depletion regions by transient-capacitance techniques.Procedure A is the conventional,con-stant voltage,deep-level transient spectroscopy(DLTS)tech-nique in which the temperature is slowly scanned and anexponential capacitance transient is assumed.Procedure B isthe conventional DLTS(Procedure A)with corrections fornonexponential transients due to heavy trap doping and incom-plete charging of the depletion region.Procedure C is a moreprecise referee technique that uses a series of isothermaltransient measurements and corrects for the same sources oferror as Procedure B.1.2 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:E 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods2E 178 Practice for Dealing with Outlying Observations2F 419 Test Method for Determining Carrier Density inSilicon Epitaxial Layers by Capacitance Voltage Measure-ments on Fabricated Junction or Schottky Diodes32.2Other Standard:MIL-STD-105 Sampling Procedures and Tables for Inspec-tion by Attributes43.Summary of Test Method3.1 In this method procedures are given for determining thedensity,activation energy,and the prefactor of the exponentialexpression for the emission rate of deep-level defect centers.InProcedureA(see Fig.1),the temperature of the diode is slowlyscanned while the bias voltage is repetitively changed.Thehigh-frequency capacitance transient due to trap emission issampled at two successively delayed gate times.The averagedifference between these sampled values constitutes the signalthat has a maximum or peak at a temperature that is a functionof the gate times.The time constant associated with the peakresponse is fixed by the rate window of the boxcar averagerused to sample the transient or by computer simulation of suchan instrument.For nonexponential transients,Procedure B addsa correction to the calculation of the time constant at thetemperature of the response peak.In Procedure C,the tempera-ture is held constant at each of a series of temperatures and theobserved capacitance transient is analyzed for its correctedtime constant.An Arrhenius-type semilogarithmic plot ofnormalized emission rate versus reciprocal temperature ismade in each procedure,and the activation energy and prefac-tor are calculated from the slope and intercept,respectively.The density of the defects is determined from the magnitude ofthe capacitance changes.3.2 The use of a boxcar averager is assumed in the discus-sion of Procedures A and B.However,a lock-in amplifier mayalso be used for these procedures,provided that factors whichmay degrade the results are taken into account.Constant-capacitance versions of these procedures are not discussed butare,of course,suitable for the purposes considered here.Thenonexponential corrections covered in this test method are ingeneral not needed for constant-capacitance measurements asthe method itself eliminates most of the nonexponentiality.4.Significance and Use4.1 Deep-level defect measurement techniques such as iso-thermal transient capacitance(ITCAP)(1,2)5and DLTS(3)utilize the ability of electrically active defects to trap free1This test method is under the jurisdiction of ASTM Committee F-1 onElectronics and is the direct responsibility of Subcommittee F01.06 on Electricaland Optical Measurement.Current edition approved June 29,1990.Published August 1990.Originallypublished as F 978 86.Last previous edition F 978 86.2Annual Book of ASTM Standards,Vol 14.02.3Annual Book of ASTM Standards,Vol 10.05.4Available from Standardization Documents Order Desk,Bldg.4 Section D,700Robbins Ave.,Philadelphia,PA 19111-5094,Attn:NPODS.5The boldface numbers in parentheses refer to the list of references at the end ofthis test method.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMcarriersandtore-emitthembythermalemission.Theoretically,the emission rate enfor electrons is given by thefollowing e