ASTM F1467-99(2005)e1

Standard Guide for Use of an X-Ray Tester ([approximate]10 keV Photons) in Ionizing Radiation Effects Testing of Semiconductor Devices and Microcircuits

SIGNIFICANCE AND USE
Electronic circuits used in many space, military and nuclear power systems may be exposed to various levels of ionizing radiation dose. It is essential for the design and fabrication of such circuits that test methods be available that can determine the vulnerability or hardness (measure of nonvulnerability) of components to be used in such systems.
Manufacturers are currently selling semiconductor parts with guaranteed hardness ratings, and the military specification system is being expanded to cover hardness specification for parts. Therefore test methods and guides are required to standardize qualification testing.  
Use of low energy (≈10 keV) X-ray sources has been examined as an alternative to cobalt-60 for the ionizing radiation effects testing of microelectronic devices (3, 4, 5, 6). The goal of this guide is to provide background information and guidance for such use where appropriate.
Note 3—Cobalt-60The most commonly used source of ionizing radiation for ionizing radiation (“total dose”) testing is cobalt-60. Gamma rays with energies of 1.17 and 1.33 MeV are the primary ionizing radiation emitted by cobalt-60. In exposures using cobalt-60 sources, test specimens must be enclosed in a lead-aluminum container to minimize dose-enhancement effects caused by low-energy scattered radiation (unless it has been demonstrated that these effects are negligible). For this lead-aluminum container, a minimum of 1.5 mm of lead surrounding an inner shield of 0.7 to 1.0 mm of aluminum is required. (See 8.2.2.2 and Practice E1249.)
The X-ray tester has proven to be a useful ionizing radiation effects testing tool because:
It offers a relatively high dose rate, in comparison to most cobalt-60 sources, thus offering reduced testing time.
The radiation is of sufficiently low energy that it can be readily collimated. As a result, it is possible to irradiate a single device on a wafer.
Radiation safety issues are more easily managed with an X-ray irradiator than w...
SCOPE
1.1 This guide covers recommended procedures for the use of X-ray testers (that is, sources with a photon spectrum having ≈10 keV mean photon energy and ≈50 keV maximum energy) in testing semiconductor discrete devices and integrated circuits for effects from ionizing radiation.  
1.2 The X-ray tester may be appropriate for investigating the susceptibility of wafer level or delidded microelectronic devices to ionizing radiation effects. It is not appropriate for investigating other radiation-induced effects such as single-event effects (SEE) or effects due to displacement damage.
1.3 This guide focuses on radiation effects in metal oxide silicon (MOS) circuit elements, either designed (as in MOS transistors) or parasitic (as in parasitic MOS elements in bipolar transistors).
1.4 Information is given about appropriate comparison of ionizing radiation hardness results obtained with an X-ray tester to those results obtained with cobalt-60 gamma irradiation. Several differences in radiation-induced effects caused by differences in the photon energies of the X-ray and cobalt-60 gamma sources are evaluated. Quantitative estimates of the magnitude of these differences in effects, and other factors that should be considered in setting up test protocols, are presented.
1.5 If a 10-keV X-ray tester is to be used for qualification testing or lot acceptance testing, it is recommended that such tests be supported by cross checking with cobalt-60 gamma irradiations.
1.6 Comparisons of ionizing radiation hardness results obtained 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 the physical effects caused by X-ray and cobalt-60 gamma irradiations is used to provide an estimate of the ratio (number-of-holes-cobalt-60)/(number-of-holes-X-ray). Several cases are defined where the differences in the effects caused...

General Information

• Status: Historical
• Publication Date: 31-Dec-2004
• ICS: 31.020 - Electronic components in general
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.11 - Nuclear and Space Radiation Effects

Relations

• Replaces: ASTM F1467-99(2005) - Standard Guide for Use of an X-Ray Tester ([approximate]10 keV Photons) in Ionizing Radiation Effects Testing of Semiconductor Devices and Microcircuits
• Effective Date: 01-Jan-2005
• Replaced By: ASTM F1467-11 - Standard Guide for Use of an X-Ray Tester (<span class='unicode'>&#x2248;</span>10 keV Photons) in Ionizing Radiation Effects Testing of Semiconductor Devices and Microcircuits
• Effective Date: 01-Oct-2011
• Referred By: ASTM F1892-12(2018) - Standard Guide for Ionizing Radiation (Total Dose) Effects Testing of Semiconductor Devices
• Effective Date: 01-Jan-2005

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation:F1467–99(Reapproved2005)
Standard Guide for
Use of an X-Ray Tester ('10 keV Photons) in Ionizing
Radiation Effects Testing of Semiconductor Devices and
Microcircuits
This standard is issued under the fixed designation F1467; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Inch-pound units were removed editorially and this guide was made a solely-SI standard in January 2011.
1. Scope holes-cobalt-60)/(number-of-holes-X-ray). Several cases are
defined where the differences in the effects caused by X rays
1.1 This guide covers recommended procedures for the use
and cobalt-60 gammas are expected to be small. Other cases
ofX-raytesters(thatis,sourceswithaphotonspectrumhaving
where the differences could potentially be as great as a factor
'10keVmeanphotonenergyand '50keVmaximumenergy)
of four are described.
in testing semiconductor discrete devices and integrated cir-
1.8 It should be recognized that neither X-ray testers nor
cuits for effects from ionizing radiation.
cobalt-60 gamma sources will provide, in general, an accurate
1.2 The X-ray tester may be appropriate for investigating
simulation of a specified system radiation environment. The
the susceptibility of wafer level or delidded microelectronic
use of either test source will require extrapolation to the effects
devices to ionizing radiation effects. It is not appropriate for
tobeexpectedfromthespecifiedradiationenvironment.Inthis
investigating other radiation-induced effects such as single-
guide, we discuss the differences between X-ray tester and
event effects (SEE) or effects due to displacement damage.
cobalt-60 gamma effects. This discussion should be useful as
1.3 This guide focuses on radiation effects in metal oxide
background to the problem of extrapolation to effects expected
silicon (MOS) circuit elements, either designed (as in MOS
from a different radiation environment. However, the process
transistors) or parasitic (as in parasitic MOS elements in
of extrapolation to the expected real environment is treated
bipolar transistors).
elsewhere (1, 2).
1.4 Information is given about appropriate comparison of
1.9 The time scale of an X-ray irradiation and measurement
ionizing radiation hardness results obtained with an X-ray
may be much different than the irradiation time in the expected
tester to those results obtained with cobalt-60 gamma irradia-
device application. Information on time-dependent effects is
tion. Several differences in radiation-induced effects caused by
given.
differences in the photon energies of the X-ray and cobalt-60
1.10 Possible lateral spreading of the collimated X-ray
gamma sources are evaluated. Quantitative estimates of the
beam beyond the desired irradiated region on a wafer is also
magnitude of these differences in effects, and other factors that
discussed.
shouldbeconsideredinsettinguptestprotocols,arepresented.
1.11 Information is given about recommended experimental
1.5 If a 10-keV X-ray tester is to be used for qualification
methodology, dosimetry, and data interpretation.
testing or lot acceptance testing, it is recommended that such
1.12 Radiation testing of semiconductor devices may pro-
tests be supported by cross checking with cobalt-60 gamma
duce severe degradation of the electrical parameters of irradi-
irradiations.
ated devices and should therefore be considered a destructive
1.6 Comparisons of ionizing radiation hardness results ob-
test.
tained with an X-ray tester with results obtained with a linac,
1.13 The values stated in SI units are to be regarded as
with protons, etc. are outside the scope of this guide.
standard. No other units of measurement are included in this
1.7 Current understanding of the differences between the
standard.
physical effects caused by X-ray and cobalt-60 gamma irradia-
1.14 This standard does not purport to address all of the
tions is used to provide an estimate of the ratio (number-of-
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
This guide is under the jurisdiction of ASTM Committee F01 on Electronics
bility of regulatory limitations prior to use.
and is the direct responsibility of Subcommittee F01.11 on Nuclear and Space
Radiation Effects.
Current edition approved Jan. 1, 2005. Published January 2005. Originally
approved in 1993. Last previous edition approved in 1999 as F1467–99. DOI: The boldface numbers in parentheses refer to the list of references at the end of
10.1520/F1467-99R05E01. this guide.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F1467–99 (2005)
2. Referenced Documents any interface with another material. This minimum distance
beinggreaterthantherangeofthemaximumenergysecondary
2.1 ASTM Standards:
electrons generated by the incident photons.
E170 TerminologyRelatingtoRadiationMeasurementsand
3.1.5 ionizing radiation effects, n—the changes in the elec-
Dosimetry
trical parameters of a microelectronic device resulting from
E666 PracticeforCalculatingAbsorbedDoseFromGamma
radiation-induced trapped charge. These are also sometimes
or X Radiation
referred to as “total dose effects.”
E668 Practice for Application of Thermoluminescence-
3.1.6 time dependent effects, n—the change in electrical
Dosimetry(TLD)SystemsforDeterminingAbsorbedDose
parameterscausedbytheformationandannealingofradiation-
in Radiation-Hardness Testing of Electronic Devices
induced electrical charge during and after irradiation.
E1249 Practice for Minimizing Dosimetry Errors in Radia-
tion Hardness Testing of Silicon Electronic Devices Using
4. Significance and Use
Co-60 Sources
E1894 Guide for Selecting Dosimetry Systems forApplica- 4.1 Electronic circuits used in many space, military and
tion in Pulsed X-Ray Sources nuclear power systems may be exposed to various levels of
2.2 International Commission on Radiation Quantities and ionizing radiation dose. It is essential for the design and
Units Reports:
fabrication of such circuits that test methods be available that
ICRU Report 33—Radiation Quantities and Units can determine the vulnerability or hardness (measure of
2.3 United States Department of Defense Standards:
nonvulnerability) of components to be used in such systems.
MIL-STD-883, Method 1019, Ionizing Radiation (Total 4.2 Manufacturers are currently selling semiconductor parts
Dose) Test Method
withguaranteedhardnessratings,andthemilitaryspecification
system is being expanded to cover hardness specification for
3. Terminology
parts. Therefore test methods and guides are required to
standardize qualification testing.
3.1 Definitions:
4.3 Use of low energy ('10 keV) X-ray sources has been
3.1.1 absorbed-dose enhancement, n—increase (or de-
examined as an alternative to cobalt-60 for the ionizing
crease)intheabsorbeddose(ascomparedwiththeequilibrium
radiation effects testing of microelectronic devices (3, 4, 5, 6).
absorbed dose) at a point in a material of interest; this can be
The goal of this guide is to provide background information
expected to occur near an interface with a material of higher or
and guidance for such use where appropriate.
lower atomic number.
3.1.2 average absorbed dose, n—mass weighted mean of
NOTE 3—Cobalt-60—The most commonly used source of ionizing
the absorbed dose over a region of interest.
radiation for ionizing radiation (“total dose”) testing is cobalt-60. Gamma
3.1.3 average absorbed-dose enhancement factor, n—ratio rayswithenergiesof1.17and1.33MeVaretheprimaryionizingradiation
emittedbycobalt-60.Inexposuresusingcobalt-60sources,testspecimens
of the average absorbed dose in a region of interest to the
must be enclosed in a lead-aluminum container to minimize dose-
equilibrium absorbed dose.
enhancement effects caused by low-energy scattered radiation (unless it
NOTE 1—For a description of the necessary conditions for measuring
has been demonstrated that these effects are negligible). For this lead-
equilibrium absorbed dose see the term “charged particle equilibrium” in
aluminum container, a minimum of 1.5 mm of lead surrounding an inner
Terminology E170 which provides definitions and descriptions of other
shield of 0.7 to 1.0 mm of aluminum is required. (See 8.2.2.2 and Practice
applicable terms of this guide. In addition, definitions appropriate to the
E1249.)
subject of this guide may be found in ICRU Report 33.
4.4 The X-ray tester has proven to be a useful ionizing
NOTE 2—The SI unit for absorbed dose is the gray (Gy), defined as one
radiation effects testing tool because:
J/kg. The commonly used unit, the rad, is defined in terms of the SI units
4.4.1 It offers a relatively high dose rate, in comparison to
by1rad = 0.01Gy.(Foradditionalinformationoncalculationofabsorbed
dose see Practice E666.) most cobalt-60 sources, thus offering reduced testing time.
4.4.2 The radiation is of sufficiently low energy that it can
3.1.4 equilibrium absorbed dose, n—absorbed dose at some
be readily collimated. As a result, it is possible to irradiate a
incremental volume within the material in which the condition
single device on a wafer.
of electron equilibrium (the energies, number, and direction of
4.4.3 Radiation safety issues are more easily managed with
charged particles induced by the radiation are constant
an X-ray irradiator than with a cobalt-60 source. This is due
throughout the volume) exists (see Terminology E170).
both to the relatively low energy of the photons and due to the
3.1.4.1 Discussion—For practical purposes the equilibrium
fact that the X-ray source can easily be turned off.
absorbed dose is the absorbed dose value that exists in a
4.4.4 X-ray facilities are frequently less costly than compa-
material at a distance in excess of a minimum distance from
rable cobalt-60 facilities.
4.5 The principal radiation-induced effects discussed in this
guide (energy deposition, absorbed-dose enhancement,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
electron-hole recombination) (see Appendix X1) will remain
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approximately the same when process changes are made to
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
improve the performance of ionizing radiation hardness of a
Available from International Commission on Radiation Units and Measure-
part that is being produced. This is the case as long as the
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814.
thicknesses and compositions of the device layers are substan-
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094. tially unchanged. As a result of this insensitivity to process
´1
F1467–99 (2005)
variables, a 10-keV X-ray tester is expected to be an excellent 6.1.1 Power Supply— The power supply typically supplies
apparatus for process improvement and control. 10 to 100 mAat 25 to 60 keV (constant potential) to the X-ray
4.6 Several published reports have indicated success in tube.
intercomparing X-ray and cobalt-60 gamma irradiations using
6.1.2 X-Ray Tube—In a typical commercial X-ray tube a
corrections for dose enhancement and for electron-hole recom-
partially focused beam of electrons strikes a water-cooled
bination. Other reports have indicated that the present under-
metal target. The target material most commonly used for
standing of the physical effects is not adequate to explain
ionizingradiationeffectstestingistungsten,thoughsomework
experimental results. As a result, it is not fully certain that the has been done using a copper target. X-ray tubes are limited by
differences between the effects of X-ray and cobalt-60 gamma
the power they can dissipate.Amaximum power of 3.5 kW is
irradiation are adequately understood at this time. (See 8.2.1 typical.
and Appendix X2.) Because of this possible failure of under-
6.1.3 Collimator—A collimator is used to limit the region
standing of the photon energy dependence of radiation effects,
on a wafer which is irradiated. A typical collimator is con-
if a 10-keV X-ray tester is to be used for qualification testing
structed of 0.0025 cm of tantalum.
or lot acceptance testing, it is recommended that such tests
6.1.4 Filter—A filter is used to remove the low-energy
should be supported by cross checking with cobalt-60 gamma
photons produced by the X-ray tube. A typical filter is 0.0127
irradiations. For additional information on such comparison,
cm of aluminum.
see X2.2.4.
6.1.5 Dosimeter—A dosimetric system is required to mea-
4.7 Because of the limited penetration of 10-keV photons,
sure the dose delivered by the X-ray tube (see Guide E1894).
ionizing radiation effects testing must normally be performed
NOTE 6—X-ray testers typically use a calibrated diode to measure the
on unpackaged devices (for example, at wafer level) or on
dose delivered by the X-ray tube. These typically provide absorbed dose
unlidded devices.
in rads(Si).
5. Interferences
6.2 Spectrum—The ionizing radiation effects produced in
5.1 Absorbed-Dose Enhancement—Absorbed-dose en-
microelectronicdevicesexposedtoX-rayirradiationaresome-
hancement effects (see 8.2.1 and X1.3) can significantly
what dependent upon the incident X-ray spectrum.As a result,
complicatethedeterminationoftheabsorbeddoseintheregion
appropriate steps shall be taken to maintain an appropriate and
of interest within the device under test. In the photon energy
reproducible X-ray spectrum.
rangeoftheX-raytester,theseeffectsshouldbeexpectedwhen
NOTE 7—The aim is to produce a spectrum whose effective energy is
there are regions of quite different atomic number within
peaked in the 5 to 15 keV photon energy region. This is accomplished in
hundreds of nanometers of the region of interest in the device
three ways. First, a large fraction of the energy output of the X-ray tube
under test.
isinthetungstenLemissionlines.Second,someofthelow-energyoutput
ofthetubeisabsorbedbyafilterpriortoitsincidenceonthedeviceunder
NOTE 4—An example of a case where significant absorbed dose
test. Third, the high-energy output of the tube is only slightly absorbed in
enhancement effects should be expected is a device with a tantalum
the sensitive regions of device under test and thus has only a small effect
silicide metallization within 200 nm of the SiO gate oxide.
on the de
...