1、Designation: F1467 99 (Reapproved 2005)1Standard Guide forUse of an X-Ray Tester (10 keV Photons) in IonizingRadiation Effects Testing of Semiconductor Devices andMicrocircuits1This standard is issued under the fixed designation F1467; the number immediately following the designation indicates the y
2、ear 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.1NOTEInch-pound units were removed editorially and this guide was
3、 made a solely-SI standard in January 2011.1. Scope1.1 This guide covers recommended procedures for the useof X-ray testers (that is, sources with a photon spectrum having10 keV mean photon energy and 50 keV maximum energy)in testing semiconductor discrete devices and integrated cir-cuits for effect
4、s from ionizing radiation.1.2 The X-ray tester may be appropriate for investigatingthe susceptibility of wafer level or delidded microelectronicdevices to ionizing radiation effects. It is not appropriate forinvestigating other radiation-induced effects such as single-event effects (SEE) or effects
5、due to displacement damage.1.3 This guide focuses on radiation effects in metal oxidesilicon (MOS) circuit elements, either designed (as in MOStransistors) or parasitic (as in parasitic MOS elements inbipolar transistors).1.4 Information is given about appropriate comparison ofionizing radiation har
6、dness results obtained with an X-raytester to those results obtained with cobalt-60 gamma irradia-tion. Several differences in radiation-induced effects caused bydifferences in the photon energies of the X-ray and cobalt-60gamma sources are evaluated. Quantitative estimates of themagnitude of these
7、differences in effects, and other factors thatshould be considered in setting up test protocols, are presented.1.5 If a 10-keV X-ray tester is to be used for qualificationtesting or lot acceptance testing, it is recommended that suchtests be supported by cross checking with cobalt-60 gammairradiatio
8、ns.1.6 Comparisons of ionizing radiation hardness results ob-tained with an X-ray tester with results obtained with a linac,with protons, etc. are outside the scope of this guide.1.7 Current understanding of the differences between thephysical effects caused by X-ray and cobalt-60 gamma irradia-tion
9、s is used to provide an estimate of the ratio (number-of-holes-cobalt-60)/(number-of-holes-X-ray). Several cases aredefined where the differences in the effects caused by X raysand cobalt-60 gammas are expected to be small. Other caseswhere the differences could potentially be as great as a factorof
10、 four are described.1.8 It should be recognized that neither X-ray testers norcobalt-60 gamma sources will provide, in general, an accuratesimulation of a specified system radiation environment. Theuse of either test source will require extrapolation to the effectsto be expected from the specified r
11、adiation environment. In thisguide, we discuss the differences between X-ray tester andcobalt-60 gamma effects. This discussion should be useful asbackground to the problem of extrapolation to effects expectedfrom a different radiation environment. However, the processof extrapolation to the expecte
12、d real environment is treatedelsewhere (1, 2).21.9 The time scale of an X-ray irradiation and measurementmay be much different than the irradiation time in the expecteddevice application. Information on time-dependent effects isgiven.1.10 Possible lateral spreading of the collimated X-raybeam beyond
13、 the desired irradiated region on a wafer is alsodiscussed.1.11 Information is given about recommended experimentalmethodology, dosimetry, and data interpretation.1.12 Radiation testing of semiconductor devices may pro-duce severe degradation of the electrical parameters of irradi-ated devices and s
14、hould therefore be considered a destructivetest.1.13 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.14 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibil
15、ity 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.1This guide is under the jurisdiction of ASTM Committee F01 on Electronicsand is the direct responsibility of Subcommittee F01.11 on Nuclear
16、and SpaceRadiation Effects.Current edition approved Jan. 1, 2005. Published January 2005. Originallyapproved in 1993. Last previous edition approved in 1999 as F146799. DOI:10.1520/F1467-99R05E01.2The boldface numbers in parentheses refer to the list of references at the end ofthis guide.1Copyright
17、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2. Referenced Documents2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetryE666 Practice for CalculatingAbsorbed Dose From Gammaor X RadiationE668 Practice for Appl
18、ication of Thermoluminescence-Dosimetry (TLD) Systems for DeterminingAbsorbed Dosein 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 Syste
19、ms for Applica-tion in Pulsed X-Ray Sources2.2 International Commission on Radiation Quantities andUnits Reports:ICRU Report 33Radiation Quantities and Units42.3 United States Department of Defense Standards:MIL-STD-883, Method 1019, Ionizing Radiation (TotalDose) Test Method53. Terminology3.1 Defin
20、itions:3.1.1 absorbed-dose enhancement, nincrease (or de-crease) in the absorbed dose (as compared with the equilibriumabsorbed dose) at a point in a material of interest; this can beexpected to occur near an interface with a material of higher orlower atomic number.3.1.2 average absorbed dose, nmas
21、s weighted mean ofthe absorbed dose over a region of interest.3.1.3 average absorbed-dose enhancement factor, nratioof the average absorbed dose in a region of interest to theequilibrium absorbed dose.NOTE 1For a description of the necessary conditions for measuringequilibrium absorbed dose see the
22、term “charged particle equilibrium” inTerminology E170 which provides definitions and descriptions of otherapplicable terms of this guide. In addition, definitions appropriate to thesubject of this guide may be found in ICRU Report 33.NOTE 2The SI unit for absorbed dose is the gray (Gy), defined as
23、oneJ/kg. The commonly used unit, the rad, is defined in terms of the SI unitsby 1 rad = 0.01 Gy. (For additional information on calculation of absorbeddose see Practice E666.)3.1.4 equilibrium absorbed dose, nabsorbed dose at someincremental volume within the material in which the conditionof electr
24、on equilibrium (the energies, number, and direction ofcharged particles induced by the radiation are constantthroughout the volume) exists (see Terminology E170).3.1.4.1 DiscussionFor practical purposes the equilibriumabsorbed dose is the absorbed dose value that exists in amaterial at a distance in
25、 excess of a minimum distance fromany interface with another material. This minimum distancebeing greater than the range of the maximum energy secondaryelectrons generated by the incident photons.3.1.5 ionizing radiation effects, nthe changes in the elec-trical parameters of a microelectronic device
26、 resulting fromradiation-induced trapped charge. These are also sometimesreferred to as “total dose effects.”3.1.6 time dependent effects, nthe change in electricalparameters caused by the formation and annealing of radiation-induced electrical charge during and after irradiation.4. Significance and
27、 Use4.1 Electronic circuits used in many space, military andnuclear power systems may be exposed to various levels ofionizing radiation dose. It is essential for the design andfabrication of such circuits that test methods be available thatcan determine the vulnerability or hardness (measure ofnonvu
28、lnerability) of components to be used in such systems.4.2 Manufacturers are currently selling semiconductor partswith guaranteed hardness ratings, and the military specificationsystem is being expanded to cover hardness specification forparts. Therefore test methods and guides are required tostandar
29、dize qualification testing.4.3 Use of low energy (10 keV) X-ray sources has beenexamined as an alternative to cobalt-60 for the ionizingradiation effects testing of microelectronic devices (3, 4, 5, 6).The goal of this guide is to provide background informationand guidance for such use where appropr
30、iate.NOTE 3Cobalt-60The most commonly used source of ionizingradiation for ionizing radiation (“total dose”) testing is cobalt-60. Gammarays with energies of 1.17 and 1.33 MeV are the primary ionizing radiationemitted by cobalt-60. In exposures using cobalt-60 sources, test specimensmust be enclosed
31、 in a lead-aluminum container to minimize dose-enhancement effects caused by low-energy scattered radiation (unless ithas been demonstrated that these effects are negligible). For this lead-aluminum container, a minimum of 1.5 mm of lead surrounding an innershield of 0.7 to 1.0 mm of aluminum is req
32、uired. (See 8.2.2.2 and PracticeE1249.)4.4 The X-ray tester has proven to be a useful ionizingradiation effects testing tool because:4.4.1 It offers a relatively high dose rate, in comparison tomost cobalt-60 sources, thus offering reduced testing time.4.4.2 The radiation is of sufficiently low ener
33、gy that it canbe readily collimated. As a result, it is possible to irradiate asingle device on a wafer.4.4.3 Radiation safety issues are more easily managed withan X-ray irradiator than with a cobalt-60 source. This is dueboth to the relatively low energy of the photons and due to thefact that the
34、X-ray source can easily be turned off.4.4.4 X-ray facilities are frequently less costly than compa-rable cobalt-60 facilities.4.5 The principal radiation-induced effects discussed in thisguide (energy deposition, absorbed-dose enhancement,electron-hole recombination) (see Appendix X1) will remainapp
35、roximately the same when process changes are made toimprove the performance of ionizing radiation hardness of apart that is being produced. This is the case as long as thethicknesses and compositions of the device layers are substan-tially unchanged. As a result of this insensitivity to process3For
36、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.4Available from International Commission on Radiation Units and Me
37、asure-ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814.5Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094.F1467 99 (2005)12variables, a 10-keV X-ray tester is expected to be an excellentapparatus for process improvement and c
38、ontrol.4.6 Several published reports have indicated success inintercomparing X-ray and cobalt-60 gamma irradiations usingcorrections for dose enhancement and for electron-hole recom-bination. Other reports have indicated that the present under-standing of the physical effects is not adequate to expl
39、ainexperimental results. As a result, it is not fully certain that thedifferences between the effects of X-ray and cobalt-60 gammairradiation are adequately understood at this time. (See 8.2.1and Appendix X2.) Because of this possible failure of under-standing of the photon energy dependence of radi
40、ation effects,if a 10-keV X-ray tester is to be used for qualification testingor lot acceptance testing, it is recommended that such testsshould be supported by cross checking with cobalt-60 gammairradiations. For additional information on such comparison,see X2.2.4.4.7 Because of the limited penetr
41、ation of 10-keV photons,ionizing radiation effects testing must normally be performedon unpackaged devices (for example, at wafer level) or onunlidded devices.5. Interferences5.1 Absorbed-Dose EnhancementAbsorbed-dose en-hancement effects (see 8.2.1 and X1.3) can significantlycomplicate the determin
42、ation of the absorbed dose in the regionof interest within the device under test. In the photon energyrange of the X-ray tester, these effects should be expected whenthere are regions of quite different atomic number withinhundreds of nanometers of the region of interest in the deviceunder test.NOTE
43、 4An example of a case where significant absorbed doseenhancement effects should be expected is a device with a tantalumsilicide metallization within 200 nm of the SiO2gate oxide.5.2 Electron-Hole RecombinationOnce the absorbed dosein the sensitive region of the device under test is determined,inter
44、pretation of the effects of this dose can be complicated byelectron-hole recombination (see 8.2.1 and X1.5).5.3 Time-Dependent EffectsThe charge in device oxidesand at silicon-oxide interfaces produced by irradiation maychange with time. Such changes take place both during andafter irradiation. Beca
45、use of this, the results of electricalmeasurements corresponding to a given absorbed dose can behighly dependent upon the dose rate and upon the time duringand after the irradiation at which the measurement takes place(see X1.7 for further detail).NOTE 5The dose rates used for X-ray testing are freq
46、uently muchhigher than those used for cobalt-60 testing. For example, cobalt-60testing is specified by Military Test Method 1019.4 to be in the range of0.5 to 3 Gy(Si)/s (50 to 300 rads/(Si)/s). For comparison, X-ray testing iscommonly carried out in the range of 2 to 30 Gy(Si)/s (200 to 3000rads(Si
47、)/s).5.4 HandlingAs in any other type of testing, care must betaken in handling the parts. This especially applies to parts thatare susceptible to electrostatic discharge damage.6. Apparatus6.1 X-Ray Tester A suitable X-ray tester (see Ref (3)consists of the following components:6.1.1 Power Supply T
48、he power supply typically supplies10 to 100 mA at 25 to 60 keV (constant potential) to the X-raytube.6.1.2 X-Ray TubeIn a typical commercial X-ray tube apartially focused beam of electrons strikes a water-cooledmetal target. The target material most commonly used forionizing radiation effects testin
49、g is tungsten, though some workhas been done using a copper target. X-ray tubes are limited bythe power they can dissipate. A maximum power of 3.5 kW istypical.6.1.3 CollimatorA collimator is used to limit the regionon a wafer which is irradiated. A typical collimator is con-structed of 0.0025 cm of tantalum.6.1.4 FilterA filter is used to remove the low-energyphotons produced by the X-ray tube. A typical filter is 0.0127cm of aluminum.6.1.5 DosimeterA dosimetric system is required to mea-sure the dose delivered by the X-ray tube (see Guide E1894).NOT
