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.
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 singleevent
effects (SEE) or effects due to displacement damage.
This guide focuses on radiation effects in metal oxide
semiconductor (MOS) circuit elements, either designed (as in MOS
transistors) or parasitic (as in parasitic MOS elements in bipolar
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.
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.
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.
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-ofholes-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
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).2
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.
Possible lateral spreading of the collimated X-ray beam beyond
the desired irradiated region on a wafer is also discussed.
Information is given about recommended experimental methodology,
dosimetry, and data interpretation.
Radiation testing of semiconductor devices may produce severe
degradation of the electrical parameters of irradiated devices and
should therefore be considered a destructive test.
The values stated in SI units are to be regarded as standard. No
other units of measurement are included in this standard.
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.
2 The boldface numbers in parentheses refer to the
list of references at the end of this guide
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