ASTM F1467-99

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

SCOPE
1.1 This guide covers recommended procedures for the use of X-ray testers (that is, sources with a photon spectrum having [approximate]10 keV mean photon energy and [approximate]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 by X rays and cobalt-60 gammas are expected to be small. Other cases where the differences could potentially be as great as a factor of four are described.
1.8 It should be recognized that neither X-ray testers nor cobalt-60 gamma sources will provide, in general, an accurate simulation of a specified system radiation environment. The use of either test source will require extrapolation to the effects to be expected from the specified radiation environment. In this guide, we discuss the differences between X-ray tester and cobalt-60 gamma effects. This discussion should be useful as background to the problem of extrapolation to effects expected from a different radiation environment. However, the process of extrapolation to the expected real environment is treated elsewhere (1, 2).  
1.9 The time scale of an X-ray irradiation and measurement may be much different than the irradiation time in the expected device application. Information on time-dependent effects is given.
1.10 Possible lateral spreading of the collimated X-ray beam beyond the desired irradiated region on a wafer is also discussed.
1.11 Information is given about recommended experimental methodology, dosimetry, and data interpretation.
1.12 Radiation testing of semiconductor devices may produce severe degradation of the electrical parameters of irradiated devices and should therefore be considered a destructive test.
1.13 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Jan-1999
• ICS: 31.020 - Electronic components in general
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.11 - Nuclear and Space Radiation Effects

Relations

• Replaced By: 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
• Referred By: ASTM F1892-12(2018) - Standard Guide for Ionizing Radiation (Total Dose) Effects Testing of Semiconductor Devices
• Effective Date: 10-Jan-1999

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
Designation:F 1467–99
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 F 1467; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope and cobalt-60 gammas are expected to be small. Other cases
where the differences could potentially be as great as a factor
1.1 This guide covers recommended procedures for the use
of four are described.
ofX-raytesters(thatis,sourceswithaphotonspectrumhaving
1.8 It should be recognized that neither X-ray testers nor
'10keVmeanphotonenergyand '50keVmaximumenergy)
cobalt-60 gamma sources will provide, in general, an accurate
in testing semiconductor discrete devices and integrated cir-
simulation of a specified system radiation environment. The
cuits for effects from ionizing radiation.
use of either test source will require extrapolation to the effects
1.2 The X-ray tester may be appropriate for investigating
tobeexpectedfromthespecifiedradiationenvironment.Inthis
the susceptibility of wafer level or delidded microelectronic
guide, we discuss the differences between X-ray tester and
devices to ionizing radiation effects. It is not appropriate for
cobalt-60 gamma effects. This discussion should be useful as
investigating other radiation-induced effects such as single-
background to the problem of extrapolation to effects expected
event effects (SEE) or effects due to displacement damage.
from a different radiation environment. However, the process
1.3 This guide focuses on radiation effects in metal oxide
of extrapolation to the expected real environment is treated
silicon (MOS) circuit elements, either designed (as in MOS
elsewhere (1, 2).
transistors) or parasitic (as in parasitic MOS elements in
1.9 The time scale of an X-ray irradiation and measurement
bipolar transistors).
may be much different than the irradiation time in the expected
1.4 Information is given about appropriate comparison of
device application. Information on time-dependent effects is
ionizing radiation hardness results obtained with an X-ray
given.
tester to those results obtained with cobalt-60 gamma irradia-
1.10 Possible lateral spreading of the collimated X-ray
tion. Several differences in radiation-induced effects caused by
beam beyond the desired irradiated region on a wafer is also
differences in the photon energies of the X-ray and cobalt-60
discussed.
gamma sources are evaluated. Quantitative estimates of the
1.11 Information is given about recommended experimental
magnitude of these differences in effects, and other factors that
methodology, dosimetry, and data interpretation.
shouldbeconsideredinsettinguptestprotocols,arepresented.
1.12 Radiation testing of semiconductor devices may pro-
1.5 If a 10-keV X-ray tester is to be used for qualification
duce severe degradation of the electrical parameters of irradi-
testing or lot acceptance testing, it is recommended that such
ated devices and should therefore be considered a destructive
tests be supported by cross checking with cobalt-60 gamma
test.
irradiations.
1.13 The values stated in International System of Units (SI)
1.6 Comparisons of ionizing radiation hardness results ob-
are to be regarded as standard. No other units of measurement
tained with an X-ray tester with results obtained with a linac,
are included in this standard.
with protons, etc. are outside the scope of this guide.
1.14 This standard does not purport to address all of the
1.7 Current understanding of the differences between the
safety concerns, if any, associated with its use. It is the
physical effects caused by X-ray and cobalt-60 gamma irradia-
responsibility of the user of this standard to establish appro-
tions is used to provide an estimate of the ratio (number-of-
priate safety and health practices and determine the applica-
holes-cobalt-60)/(number-of-holes-X-ray). Several cases are
bility of regulatory limitations prior to use.
defined where the differences in the effects caused by X rays
2. Referenced Documents
2.1 ASTM Standards:
This guide is under the jurisdiction ofASTM Committee F-1 on Electronicsand
is the direct responsibility of Subcommittee F01.11 on Quality and Hardness
Assurance.
Current edition approved Jan. 10, 1999. Published March 1999. Originally The boldface numbers in parentheses refer to the list of references at the end of
published as F 1467–93. Last previous edition F 1467–94. this guide.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1467
E 170 Terminology Relating to Radiation Measurements radiation-induced trapped charge. These are also sometimes
and Dosimetry referred to as “total dose effects.”
E666 PracticeforCalculatingAbsorbedDosefromGamma
3.1.6 time dependent effects, n—the change in electrical
or X-Radiation
parameterscausedbytheformationandannealingofradiation-
E 668 Practice for theApplication of Thermoluminescence-
induced electrical charge during and after irradiation.
Dosimetry(TLD)SystemsforDeterminingAbsorbedDose
in Radiation-Hardness Testing of Electronic Devices
4. Significance and Use
E 1249 Practice for Minimizing Dosimetry Errors in Radia-
4.1 Electronic circuits used in many space, military and
tion Hardness Testing of Silicon Electronic Devices Using
nuclear power systems may be exposed to various levels of
Cobalt-60 Sources
ionizing radiation dose. It is essential for the design and
E 1894 Guide for Selecting Dosimetry Systems for Appli-
fabrication of such circuits that test methods be available that
cation in Pulsed X-Ray Sources
can determine the vulnerability or hardness (measure of
2.2 International Commission on Radiation Quantities and
nonvulnerability) of components to be used in such systems.
Units Reports:
4.2 Manufacturers are currently selling semiconductor parts
ICRU Report 33—Radiation Quantities and Units
with guaranteed hardness ratings, and the military specification
2.3 United States Department of Defense Standards:
system is being expanded to cover hardness specification for
MIL-STD-883, Method 1019, Ionizing Radiation (Total
parts. Therefore test methods and guides are required to
Dose) Test Method
standardize qualification testing.
4.3 Use of low energy ('10 keV) X-ray sources has been
3. Terminology
examined as an alternative to cobalt-60 for the ionizing
3.1 Definitions:
radiation effects testing of microelectronic devices (3, 4, 5, 6).
3.1.1 absorbed-dose enhancement, n—increase (or de-
The goal of this guide is to provide background information
crease)intheabsorbeddose(ascomparedwiththeequilibrium
and guidance for such use where appropriate.
absorbed dose) at a point in a material of interest; this can be
expected to occur near an interface with a material of higher or
NOTE 3—Cobalt-60—The most commonly used source of ionizing
radiation for ionizing radiation (“total dose”) testing is cobalt-60. Gamma
lower atomic number.
rayswithenergiesof1.17and1.33MeVaretheprimaryionizingradiation
3.1.2 average absorbed dose, n—mass weighted mean of
emittedbycobalt-60.Inexposuresusingcobalt-60sources,testspecimens
the absorbed dose over a region of interest.
must be enclosed in a lead-aluminum container to minimize dose-
3.1.3 average absorbed-dose enhancement factor, n—ratio
enhancement effects caused by low-energy scattered radiation (unless it
of the average absorbed dose in a region of interest to the
has been demonstrated that these effects are negligible). For this lead-
equilibrium absorbed dose.
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
NOTE 1—For a description of the necessary conditions for measuring
E 1249.)
equilibrium absorbed dose see the term “charged particle equilibrium” in
Terminology E 170 which provides definitions and descriptions of other
4.4 The X-ray tester has proven to be a useful ionizing
applicable terms of this guide. In addition, definitions appropriate to the
radiation effects testing tool because:
subject of this guide may be found in ICRU Report 33.
4.4.1 It offers a relatively high dose rate, in comparison to
NOTE 2—The SI unit for absorbed dose is the gray (Gy), defined as one
most cobalt-60 sources, thus offering reduced testing time.
J/kg. The commonly used unit, the rad, is defined in terms of the SI units
by 1 rad 5 0.01 Gy. (For additional information on calculation of 4.4.2 The radiation is of sufficiently low energy that it can
absorbed dose see Practice E 666.)
be readily collimated. As a result, it is possible to irradiate a
single device on a wafer.
3.1.4 equilibrium absorbed dose, n—absorbed dose at some
4.4.3 Radiation safety issues are more easily managed with
incremental volume within the material in which the condition
an X-ray irradiator than with a cobalt-60 source. This is due
of electron equilibrium (the energies, number, and direction of
both to the relatively low energy of the photons and due to the
charged particles induced by the radiation are constant
fact that the X-ray source can easily be turned off.
throughout the volume) exists (see Terminology E 170).
4.4.4 X-ray facilities are frequently less costly than compa-
3.1.4.1 Discussion—For practical purposes the equilibrium
absorbed dose is the absorbed dose value that exists in a rable cobalt-60 facilities.
material at a distance in excess of a minimum distance from 4.5 The principal radiation-induced effects discussed in this
any interface with another material. This minimum distance guide (energy deposition, absorbed-dose enhancement,
being greater than the range of the maximum energy secondary electron-hole recombination) (see Appendix X1) will remain
electrons generated by the incident photons. approximately the same when process changes are made to
3.1.5 ionizing radiation effects, n—the changes in the elec- improve the performance of ionizing radiation hardness of a
trical parameters of a microelectronic device resulting from part that is being produced. This is the case as long as the
thicknesses and compositions of the device layers are substan-
tially unchanged. As a result of this insensitivity to process
Annual Book of ASTM Standards, Vol 12.02.
variables, a 10-keV X-ray tester is expected to be an excellent
Available from International Commission on Radiation Units and Measure-
apparatus for process improvement and control.
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814.
4.6 Several published reports have indicated success in
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094. intercomparing X-ray and cobalt-60 gamma irradiations using
F 1467
corrections for dose enhancement and for electron-hole recom- 6.1.2 X-Ray Tube—In a typical commercial X-ray tube a
bination. Other reports have indicated that the present under- partially focused beam of electrons strikes a water-cooled
standing of the physical effects is not adequate to explain metal target. The target material most commonly used for
experimental results. As a result, it is not fully certain that the ionizingradiationeffectstestingistungsten,thoughsomework
differences between the effects of X-ray and cobalt-60 gamma has been done using a copper target. X-ray tubes are limited by
irradiation are adequately understood at this time. (See 8.2.1 the power they can dissipate. A maximum power of 3.5 kW is
and Appendix X2.) Because of this possible failure of under- typical.
standing of the photon energy dependence of radiation effects, 6.1.3 Collimator—A collimator is used to limit the region
if a 10-keV X-ray tester is to be used for qualification testing on a wafer which is irradiated. A typical collimator is con-
or lot acceptance testing, it is recommended that such tests structed of 0.0025 cm of tantalum.
should be supported by cross checking with cobalt-60 gamma 6.1.4 Filter—A filter is used to remove the low-energy
irradiations. For additional information on such comparison, photons produced by the X-ray tube. A typical filter is 0.0127
see X2.2.4. cm (0.005 in.) of aluminum.
4.7 Because of the limited penetration of 10-keV photons, 6.1.5 Dosimeter—A dosimetric system is required to mea-
ionizing radiation effects testing must normally be performed sure the dose delivered by the X-ray tube (see Guide E 1894).
on unpackaged devices (for example, at wafer level) or on
NOTE 6—X-ray testers typically use a calibrated diode to measure the
unlidded devices.
dose delivered by the X-ray tube. These typically provide absorbed dose
in rads(Si).
5. Interferences
6.2 Spectrum—The ionizing radiation effects produced in
5.1 Absorbed-Dose Enhancement—Absorbed-dose en-
microelectronic devices exposed to X-ray irradiation are some-
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
of the tube is absorbed by a filter prior to its incidence on the device under
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 device. (See X1.2 for further detail.)
5.2 Electron-Hole Recombination—Once the absorbed dose
6.2.1 Control of Spectrum—The following steps shall be
in the sensitive region of the device under test is determined,
taken to insure adequate control of the X-ray spectrum:
interpretation of the effects of this dose can be complicated by
6.2.1.1 Anode Material— Unless otherwise specified, the
electron-hole recombinati
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