1、Designation: E1855 10Standard Test Method forUse of 2N2222A Silicon Bipolar Transistors as NeutronSpectrum Sensors and Displacement Damage Monitors1This standard is issued under the fixed designation E1855; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n 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 test method covers the use of 2N2222A siliconbipolar transistors as dosimetry
3、 sensors in the determination ofneutron energy spectra, and as silicon 1-MeV(Si) equivalentdisplacement damage fluence monitors.1.2 The neutron displacement damage is especially valuableas a neutron spectrum sensor in the range 0.1 to 2.0 MeV whenfission foils are not available. It has been applied
4、in the fluencerange between 2 3 1012n/cm2and 1 3 1014n/cm2and shouldbe useful up to 1015n/cm2. This test method details the stepsfor the acquisition and use of silicon 1-MeV equivalent fluenceinformation (in a manner similar to the use of activation foildata) for the determination of neutron spectra
5、.1.3 In addition, this sensor can provide important confirma-tion of neutron spectra determined with other sensors, andyields a direct measurement of the silicon 1-MeV fluence bythe transfer technique.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are
6、included in thisstandard.1.5 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 requirements pr
7、ior to use.2. Referenced Documents2.1 The ASTM standards E170, E261, and E265 provide abackground for understanding how sensors are used in radia-tion measurements and general dosimetry. The rest of thestandards referenced in the list discuss the choice of sensors,spectrum determinations with sensor
8、 data, and the prediction ofneutron displacement damage in some semiconductor devices,particularly silicon.2.2 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE265 Tes
9、t Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32E720 Guide for Selection and Use of Neutron Sensors forDetermining Neutron Spectra Employed in Radiation-Hardness Testing of ElectronicsE721 Guide for Determining Neutron Energy Spectra fromNeutron Sensors
10、 for Radiation-Hardness Testing of Elec-tronicsE722 Practice for Characterizing Neutron Fluence Spectrain Terms of an Equivalent Monoenergetic Neutron Fluencefor Radiation-Hardness Testing of ElectronicsE844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706(IIC)E944 Guide fo
11、r Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)E1854 Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic PartsE2005 Guide for Benchmark Testing of Reactor Dosimetryin Standard and Reference Neutron FieldsE2450 Practic
12、e for Application of CaF2(Mn) Thermolumi-nescence Dosimeters in Mixed Neutron-Photon Environ-ments3. Terminology3.1 Symbols:F1= the silicon 1-MeV equivalent fluence (see Practice E722).hFE= ic/ibwhere icis the collector current and ibis the basecurrent, in a common emitter circuit.4. Summary of Test
13、 Method4.1 Gain degradation of 2N2222Asilicon bipolar transistorsmeasured in a test (simulation) environment is compared with1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.07 on Radiation Dosi
14、metry for Radiation Effects on Materials and Devices.Current edition approved Oct. 1, 2010. Published October 2010. Originallyapproved in 1996. Last previous edition approved in 2005 as E1855 051. DOI:10.1520/E1855-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AS
15、TM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.that measured in a reference
16、 neutron environment. The F1rinthe reference environment is derived from the known referencespectrum and is used to determine a measured F1tin the testenvironment (1,2)3by the transfer technique. The subscripts rand t refer to the reference and test environments respectively.4.2 The measured F1tmay
17、be used as a sensor response ina spectrum adjustment code in a manner similar to the use ofreaction foil activities to determine the spectrum (3,4).4.3 Spectra compatible with the responses of many sensorsmay be used to calculate a more reliable measure of thedisplacement damage.5. Significance and
18、Use5.1 The neutron spectrum in a test (simulation) environmentmust be known in order to use a measured device response inthe test environment to predict the device performance in anoperational environment (see Practice E1854). Typically, neu-tron spectra are determined by use of a set of sensors tha
19、t haveresponse functions that are sensitive over the neutron energyregion to which the device under test (DUT) responds (seeGuide E721). In particular, for silicon bipolar devices exposedin reactor neutron spectra, this effective energy range isbetween 0.01 and 10 MeV. A typical set of activation re
20、actionsthat lack fission reactions from nuclides such as235U,237Np,or239Pu, will have very poor sensitivity to the spectrumbetween 0.01 and 2 MeV. For a pool-type reactor spectrum, 70% of the DUT electronic damage response may lie in thisrange. Often, fission foils are not included in the sensor set
21、 forspectrum determinations because their use must be licensed,and they require special handling for health physics consider-ations. The silicon transistors provide the needed response todefine the spectrum in this critical range.5.2 If fission foils are a part of the sensor set, the siliconsensor p
22、rovides confirmation of the spectrum shape.5.3 Bipolar transistors, such as type 2N2222A, are inexpen-sive, are smaller than fission foils contained in a boron ball, andare sensitive to a part of the neutron spectrum important to thedamage of modern silicon electronics. They also can be useddirectly
23、 in arrays to map 1-MeV(Si) equivalent fluence. Theproper set of steps to take in reading the transistor-gaindegradation is the primary subject of this test method.5.4 Fig. 1 shows the energy-dependence of the displacementdamage function for silicon.As can be seen from the figure, themajor portion o
24、f the response for the silicon transistors willgenerally be above 100 keV. The currently recommendedsilicon damage function is listed in Practice E722.6. Apparatus6.1 A transistor with demonstrated response in agreementwith calculated F1values in widely varied environments is thesilicon bipolar tran
25、sistor 2N2222A. It is recommended thatthree or more of these transistors be calibrated together andused at each location to be characterized. At least three othersshould be used as temperature correction devices (controldevices) during readout. The control transistors should beexposed one time to a
26、calibration exposure of about 1.0 3 1013n/cm21-MeV(Si) equivalent fluence and then annealed (bakedout) at 180C for 24 h followed by ambient air cooling beforebeing used as controls. These control transistors are notexposed again to radiation during the testing steps, but are readwith the exposed tra
27、nsistors to provide temperature correction.6.2 A dry oven for annealing is needed to stabilize the gainafter both the calibration-exposure and gain readout are com-pleted for the reference environment. The oven shall be able tomaintain the set temperature to within 63.0C at 80C and at180C. It would
28、be prudent to have a timer for automaticshutdown and an emergency power system (UPS). Shutdownwith a timer will require a door-opening mechanism forambient air-cooling.6.3 An electronic system is required to maintain appropriatetransistor bias and currents and to read the currents for the gain3The b
29、oldface numbers in parentheses refer to a list of references at the end ofthis test method.FIG. 1 Silicon Displacement Damage Response FunctionE1855 102measurements. It is recommended that a programmable semi-conductor parameter tester (such as a Hewlett Packard 4145A)be used. A programmable tester
30、can operate in pulsed mode tocontrol heating effects and provide gain values quickly. Theparameter tester determines the common emitter current gainby injecting a pulse of current into the base region, measuringthe collector current, and determining the current ratio ic/ibata fixed bias of 10 V. The
31、 bias voltage is measured between thecollector and the base (see Ref (5).6.4 A reference neutron source (see Guide E2005) forcalibration of the transistors is required. The neutron fluenceand neutron fluence spectrum of the reference source must beknown. National Institute for Standards and Technolo
32、gy(NIST) benchmark fields (6) are recommended for use asprimary standards, and a well characterized Fast Burst Reactor(FBR), such as the one at White Sands Missile Range, isrecommended as a reference benchmark field.6.5 A suitable monitor such as a nickel foil should beexposed along with the transis
33、tors during calibration to relateto the magnitude of the neutron fluence. A photon-sensitivedetector such as a CaF2thermoluminescent detector (TLD)shall be included in each test package to monitor the gamma-ray dose so that a correction can be made for the transistordamage from gamma-rays. Care must
34、 be taken in the determi-nation of the gamma environment to correct for any neutronresponse from the photon-sensitive detector that is used.Practice E2450 provides guidance on how to correct aCaF2:Mn TLD for the neutron response.NOTE 1Ionizing dose is produced by photon irradiation in the bulksilico
35、n and SiO2. The ionizing dose can induce trapped holes and interfacestates in the oxide of the silicon devices. This resulting trapped charge caninduce electric fields that change the gain in a bipolar device.7. Description of the Test Method7.1 2N2222A transistors exhibit a range of initial gainval
36、ues and responses, but each responds linearly with1-MeV(Si) equivalent fluence, F1, at fixed collector currentaccording to the Messenger-Spratt equation (7), if gamma raysdo not contribute to the change of gain.1hFEF21hFEO5 KtF1 MeV! (1)The term hFEOis the common emitter current gain at somefixed co
37、llector current before irradiation in the test environ-ment, and hFEFis the same quantity measured at the samecollector current after irradiation. Ktis the damage constant. Ifgamma-ray dose contributes to the change in the reciprocal ofthe gain, then that contribution must be subtracted from the lef
38、tside of Eq 1 (see 8.3).7.2 A semiconductor parameter analyzer may be used todetermine hFE. A basic schematic circuit used by semiconduc-tor analyzers for measuring hFE= ic/ibis shown in Fig. 2. Anyequivalent method for making the electrical measurement isacceptable but the experimenter must ensure
39、that the currentsdo not exceed the limits detailed in 8.1.2 and 8.1.3.7.3 Since Ktdiffers for each transistor, each must becalibrated. When the technology of manufacture is such thatthe Kts within a batch are the same to within a few percentagepoints, a calibration by batch may be satisfactory. A ty
40、picalvalue for Ktis about 1.5 3 1015cm2/neutron for a collectorcurrent of 1 mA.7.4 The linearity of response of a given batch of transistorsshall be verified by exposure of samples of the batch to at leastthree levels of neutron fluence covering the range in which thedevices will be used.7.5 The cal
41、ibration is accomplished by exposing the tran-sistors in a reference field for which the absolute values of theneutron fluence spectrum are known over the neutron energyrange in which significant damage is caused. The 1-MeV(Si)equivalent fluence of the reference environment, F1r,isob-tained by foldi
42、ng the spectrum with the silicon displacementdamage response as is described in Practice E722. The gainvalues, hFEObefore irradiation, and hFEFafter irradiation aremeasured, and the left side of Eq 1 is calculated. The followingquantity can be defined.DS1hD51hFEF21hFEO(2)This is the change in recipr
43、ocal gain.Asubscript of r is usedto denote the reciprocal gain change in the reference calibrationenvironment. A subscript of t is used to denote the reciprocalgain change in the test or unknown environment. This mea-surement and the known value of F1rin the referenceenvironment provide the calibrat
44、ion for the transistor, Kt.7.6 When the D (1/h) is measured in the unknown testenvironment, the F1tcan be found in the following manner.Take the ratio of equations (Eq 1) for the reference and testenvironments and rearrange the terms to yield Eq 3 (see Ref(3).F1t5DS1hDtDS1hDrF1r51KtDS1hDt(3)7.7 The
45、F1tis the quantity needed as a sensor value in thespectrum determination procedure. The D (1/h)tis the changein the reciprocal gain induced by the test environment. Forneutron damage on 2N2222A transistors, Ktis a constant forneutron fluences up to about 1015n/cm2. The method describedhere provides
46、a direct determination of F1t.8. Experimental Procedure8.1 To ensure proper calibration of the sensor, follow thesteps described in 8.1.1-8.1.9.8.1.1 Step 1The 2N2222Atransistors are inexpensive andcan be purchased in large lots from electronic supply houses.FIG. 2 Schematic for Transistor Read-OutE
47、1855 103Those purchased from readily available commercial sourceshave been found to be fairly uniform in electrical propertiesand come with initial gains between about 50 and 200. The firststep is to measure, at 1 mA collector current, the initial gainvalues of all the transistors in the batch. Thro
48、w out all thosewith gain less than 100, and then remove the top and bottom5 % of the remaining set. If the calibration environment is largeenough to provide a uniform fluence to all the transistors on thesame run, it is best to calibrate the whole batch together. Theminimum number of transistors sho
49、uld be three.8.1.2 The gain measurements may conveniently be madewith a programmable semiconductor parameter analyzer, orwith a specially designed circuit tester. The measurementdetails provided in 8.1.2.1-8.1.2.6 correspond to the steps on anHP 4145A programmable semiconductor parameter analyzerwith an HP16058A Test Fixture. Any equivalent method formaking the electrical measurement is acceptable as long as thecurrents do not exceed the limits detailed in 8.1.2 and 8.1.3.The manuals for other parameter analyzers can be used to seehow this procedure should be adopted t
