ISSN 10637397, Russian Microelectronics, 2013, Vol. 42, No. 7, pp. 420–423. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © P.K. Skorobogatov, 2012, published in Izvestiya Vysshikh Uchebnykh Zavedenii. Elektronika, 2012, No. 5, pp. 39–43.
The use of pulse laser sources for simulating vol
ume (transient) ionization effects in semiconductors
and microcircuits is based on the abilities of quanta
with energies that exceed the forbidden gap width of
the semiconductor to ionize the device volume .
The multiple performed studies and experiments [2–4]
confirmed the efficiency of laser ionization sources
and revealed a number of factors limiting their appli
cation. One of the most important factors is the
restriction related to the nonuniformity of ionizing the
device volume due to its surface metallization shading.
ANALYSIS OF THE LASER RADIATION
TRANSMISSION IN THE LAWS
OF GEOMETRICAL OPTICS
The basic features of the influence of surface met
allization in the “on top” microcircuit irradiation
conditions can be analyzed on the optical model,
shown in Fig. 1.
The metallization effect can be repro
duced by a set of
lightnontransmitting strips, recur
ring with period
, the distance between which is equal
. When the wavelength of the light radiation is
much smaller than the metallization period, the laws
of geometrical optics act, in accordance with which
the plane wave of radiation forms sharp shadows deep
inside the semiconductor.
Studies [3, 4] showed that, when the metallic
transition coverage is up to 75%, the metallization
strip width is up to 20
m, and the laser radiation is of
a relatively low intensity (about 10
responding to the equivalent absorbed dose rate of
rad (Si)/s), the metallization weakly effects the
shape of the ionization current of the
This is attributed to the fact that, for the operation
time of the laser radiation pulse (10–15 ns), the side
diffusion of nonequilibrium charge carriers has time to
virtually equalize their concentration over the semi
conductor volume, and the metallization effect is
taken into account by using the correction metalliza
tion transmission factor :
= 1 –
= 1 –
is the crystal area occupied by
is the surface area of the crystal.
= 1 –
takes into account atten
uation of the light flux by the metal and is determined
in the process of the dosimetric maintenance of tests.
The possibility of using a relatively simple expression
for evaluating the metallization effect is based on the
laws of geometrical optics, which are true only for the
wavelength of the laser radiation, which substantially
exceeds the typical sizes of the metallization strips .
When the radiation wavelength of Radon laser simula
tors, being 1.06–1.08
m in the fundamental har
monic conditions, is used, the applicability limit of the
simple geometrical approximation is limited by small
Laser Simulation of Volume Ionization Effects
in Submicron VLSI circuits
P. K. Skorobogatov
National Research Nuclear University MIFI, Moscow, Russia
Received April 26, 2012
—The adequacy of the laser simulation of volume ionization effects (dose rate) in microcircuits is
violated due to the influence of surface metallization. It is shown that the optical diffraction of the laser emis
sion restricts possible applications of this method by 0.18
m design rules and higher.
dose rate, laser simulation, metallization, diffraction
Optical model for evaluating the metallization
effect on laser radiation transmission in a semiconductor.