1063-7397/00/2906- $25.00 © 2000 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 29, No. 6, 2000, pp. 391–396. Translated from Mikroelektronika, Vol. 29, No. 6, 2000, pp. 442–448.
Original Russian Text Copyright © 2000 by Budagyan, Sherchenkov, Berdnikov, Chernomordik.
Today, amorphous hydrogenated a-Si (a-Si : H) is
used largely in photoelectric devices (solar cells, radia-
tion detectors, etc.). These devices fully exploit the
basic advantages of this material: high absorption coef-
ﬁcient, high photosensitivity in the visible spectral
range, the possibility of fabricating large-area semicon-
ducting structures, low process cost, the compatibility
with conventional IC technologies, and others . Fur-
ther application of this and related materials in solid-
state devices requires that two fundamental problems in
physics and technology of disordered semiconductors
be tackled. These are (1) a considerable increase in the
growth rate of the ﬁlms with a low defect concentration
) and high photosensitivity (~10
called device-grade ﬁlms) and (2) an increase in the sta-
bility of a-Si ﬁlm properties to various external actions
(long-term radiation, high temperature, etc.).
In this work, we report a high-rate method for the
deposition of a-Si : H ﬁlms in a low-frequency glow
discharge initiated at 55 kHz. The structure and proper-
ties of the ﬁlms were also investigated.
At present, a-Si : H ﬁlms are basically obtained by
decomposing silane-containing gaseous mixtures in a
plasma of a glow discharge initiated at 13.56 MHz [1, 2].
The growth rate in this case is low (about 1 Å/s), which
limits the industrial use of this technique. The growth
rate is usually raised by increasing the discharge power;
however, ﬁlms thus obtained become structurally inho-
mogeneous, their electronic properties degrade, and the
stability severely worsens .
Over recent years, new growth methods have been
reported. In particular, it has been suggested to use a
high-frequency (30–170 MHz) glow discharge, which
signiﬁcantly improves the growth rate (to 20 Å/s) and,
at the same time, preserves the device grade of the ﬁlms
. However, the ﬁlms obtained under such conditions
are, as a rule, structurally inhomogeneous. Therefore, a
number of practical issues, such as stability and inter-
face quality in heterostructures, remain unsolved.
We will consider the properties and stability of the
ﬁlms and also electronic states at the interfaces of het-
erostructures based on these ﬁlms.
The setup for the deposition of a-Si : H ﬁlms in a
low-frequency glow discharge plasma is shown in Fig. 1.
It consists of a tubular quartz reactor with coaxially
arranged resistive heater and four graphite electrodes.
The electrodes, running parallel to the gas ﬂow, serve
also as substrate holders. The plasma is initiated
between two pairs of the holders. The alternate holders
are connected to the balanced output of the generator in
pairs. The reactor was evacuated with an oil fore pump
through a throttle valve, which maintains a desired
pressure. The ﬂow rate of a working gas (100% SiH
chamber pressure, discharge power, and substrate tem-
perature were varied within 50–200 sccm, 40–190 Pa,
50–400 W, and
C, respectively. Deposition was
carried out both in a continuous discharge and in a low-
frequency discharge modulated by pulses of certain
duration and duty ratio. Physicochemical processes
taking place in the plasma were studied by optical
emission spectroscopy and mass spectrometry. In addi-
tion, the discharge electrical characteristics were mea-
a-Si : H ﬁlms were deposited on glass (Corning
7059), quartz, and single-crystal KDB-10 (boron-
doped, resistivity 10
cm) silicon substrates. To take
measurements, aluminum contacts were applied on the
ﬁlms either through a mask or by photolithography.
The structure of the ﬁlms was examined by atomic
force microscopy (AFM) , IR spectroscopy , elec-
tron paramagnetic resonance (EPR) , and differen-
tial scanning calorimetry . The total concentration
of bonded hydrogen in the film and microstructure
High-Rate Deposition of Amorphous Silicon
B. G. Budagyan*, A. A. Sherchenkov*, A. E. Berdnikov**, and V. D. Chernomordik**
Moscow Institute of Electronic Engineering (Technical University), Zelenograd, Moscow oblast, Russia
Institute of Microelectronics, Russian Academy of Sciences, ul. Universitetskaya 21, Yaroslavl, 150007 Russia
Received January 17, 2000
—A method for rapid deposition of amorphous silicon (a-Si) ﬁlms in a low-frequency (55 kHz) glow
discharge plasma is suggested. The structure and electrophysical properties of the ﬁlms were investigated. It is
shown that the use of the low-frequency discharge makes it possible to independently control the stability and
concentration of recombination centers in a-Si. This fact, along with the possibility of fabricating heterostruc-
tures with a low density of surface states, makes this method promising for mass production of a-Si-based elec-