1063-7397/02/3104- $27.00 © 2002 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 31, No. 4, 2002, pp. 257–259. Translated from Mikroelektronika, Vol. 31, No. 4, 2002, pp. 303–306.
Original Russian Text Copyright © 2002 by Panﬁlov.
Polarity-dependent electrical mass transfer is found
in both bulk  and planar  silicon structures. It con-
sists in electronic processes and the transfer of the elec-
trode material into the interelectrode space under the
action of appropriate electric signals. As a result, the
electrodes may become connected via a highly con-
ducting, metal-like bridge formed from the eutectic
alloy of the electrode metal and silicon. Afterward, the
mass transfer may break the bridge or change its resis-
tance by modifying its cross section. The bridge can be
regarded as a nonvolatile component: it retains its state
after the power supply is switched off. In addition, it
possesses elevated radiation and thermal stability. In
this form, polarity-dependent electrical mass transfer
was discovered at the Institute of Radio Engineering
and Electronics, Russian Academy of Sciences .
To ascertain the mechanism of polarity-dependent
mass transfer in silicon, one should address the forma-
tion of the metal-like bridge. This would give at least a
general understanding of physical processes that
remove the metal-like alloy from the interelectrode
space and modify the cross section of the bridge.
The ﬁrst question to be answered concerns the loca-
tion and shape of the bridge. For bulk structures, one
can easily ﬁnd where the bridge is located, so we pro-
ceed to the planar design.
There are three ways in which the bridge may be
(1) The bridge is formed by the spreading of a
metal-like alloy over the surface of silicon or, probably,
silicon dioxide under the action of an electric ﬁeld. The
surface is the projection of a thermal ﬁlament formed in
the bulk silicon. It can be shown by calculation or
experiment that the conditions for the formation of a
thermal ﬁlament are fulﬁlled. The process also involves
the Laplace forces, electrocapillarity, etc., . In this
case, the bridge should be situated on the surface of sil-
icon (or silicon dioxide) and the bridge cross section
should be a distorted circle.
(2) The bridge is formed as a result of the ﬁrst stage
(kinetic regime) of a physico-chemical process that
consists in the spreading of the liquid metal over the sil-
icon surface, which is the projection of the thermal ﬁl-
ament . In this case, the bridge should be situated on
the silicon surface under the silicon dioxide layer and
should appear as a strip.
(3) The bridge is formed in the region of the thermal
ﬁlament. In this case, it should lie in the bulk silicon
and have a circular cross section.
This paper outlines experimental results concerning
the location and shape of the metal-like bridge. The
experiment employed the angle-lap method.
According to the angle-lap method , the speci-
men is ground to a small angle
with respect to the
plane of its surface and the lap is analyzed with a
microscope in order to determine the distribution of
objects of interest in depth.
The model shown in Fig. 1 was used in this work.
The silicon wafer is covered with an oxide layer of
. A circular metallic wire of radius
located at a depth
. The angle lap is made along the
at an angle
with the wafer surface. It
follows from Fig. 1 that the
region is a virgin
portion of the wafer surface. The
region is the
lap across the oxide,
is the lap across the silicon,
is the lap across the wire. It follows from
Fig. 1 that
. The depth of the wire is
Polarity-Dependent Electrical Mass Transfer in Silicon:
The Location and Shape of the Metal-like Bridge
B. A. Panfilov
Institute of Radio Engineering and Electronics (Fryazino Branch), Russian Academy of Sciences, pl. Vvedenskogo 1,
Fryazino, Moscow oblast, 141120 Russia
Received November 26, 2001
—It is demonstrated that knowing the location and shape of the metal-like bridge is vital for under-
standing the mechanism and constructing a physical model of polarity-dependent electrical mass transfer in sil-
icon. A model of a silicon structure with the metal-like bridge is described. Experimental results on the deter-
mination of the location and shape of the bridge by the angle-lap method and the model are presented. They
imply that the bridge is formed in the bulk and has an almost cylindrical shape. This enables us to formulate
fundamental concepts of a qualitative physical model for the phenomenon.