ISSN 10637397, Russian Microelectronics, 2011, Vol. 40, No. 6, pp. 371–378. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.M. Efremov, A.V. Yudina, V.I. Svettsov, 2011, published in Mikroelektronika, 2011, Vol. 40, No. 6, pp. 405–412.
371
1. INTRODUCTION
The lowtemperature gasdischarge plasma of the
mixtures of hydrogen halogenides HX (X = Cl, Br, I)
with noble (Ar, He) and molecular (
H
2
, O
2
, N
2
) gases
had found the application in the technology of micro
and nanoelectronics upon carrying out dry etching
and cleaning the surface of semiconductor wafers and
functional layers of integrated microcircuits [1, 2].
Interest in binary systems is based on the possibility of
flexibly controlling the plasma parameters, concentra
tions of active particles, and, as a consequence, the
final effect of the treatment of the material upon vary
ing the initial composition of the plasmaforming
mixture. For example, it was shown [3] that the hydro
gen addition to HBr provides a decrease in the rough
ness and conservation of the stoichiometric composi
tion of the treated surface upon etching III–V semi
conductors (mainly GaAs, AlGaAs, and InP).
The main advantages of HCl in comparison with
conventional chlorinecontaining gases (
BCl
3
, CCl
4
,
Cl
2
) are as follows: (i) the absence of deposition of
solid products of plasmachemical reactions on the
surfaces in contact with plasma and (ii) the lower con
centrations of chlorine atoms and the ratios of the
density of neutral and charged particles compared
with the
Cl
2
plasma [4, 5]. The latter leads to better
characteristics of anisotropy and selectivity of the pro
cess with an insignificant loss in the rate. Unfortu
nately, the potential advantages of HClbased binary
mixtures are not realized in full because of insufficient
knowledge of the mechanisms of physicochemical
processes determining the steadystate parameters and
composition of the plasma. The absence of such infor
mation does not provide the optimal modes of carry
ing out the etching processes with the use of the HCl
plasma and does not determine the ways of searching
and the criteria of attaining optimality.
It was previously shown that the addition of noble
gas to chemically active gas (for example, to
Cl
2
[6, 7],
BCl
3
[8], or HCl [9]) plays the role of not only an inert
diluent but also affects the kinetics of plasmachemical
processes through the variation in electrical parameters
of the plasma. The goal of this work was the model anal
ysis of these questions as applied to the
HCl–H
2
plasma
in the conditions of a dc glow discharge.
2. METHODICAL PART
2.1. Experimental Installation and Procedure
To investigate experimentally the parameters of the
dc glow discharge plasma in HCl, we used a glass
cylindrical flow reactor (with radius
r
= 0.9 cm and
length
l
= 40 cm). The external (specified) parameters
of the discharge were the discharge current (
i
p
= 15–
35 mA), the gas pressure (
p
= 40–200 Pa), and the gas
consumption (
q
= 2 cm
3
/s under the standard condi
tions). The temperature of neutral particles (
T
) was
calculated when solving the heat balance equation of
the reactor [10] with the use of the experimental data
on the temperature of the outer wall. The probe diag
nostics provided the data on the axial electric field
strength in the zone of the positive discharge column
(
E
). When determining the reduced field strength
E
/
N
(
N
=
p
/
k
B
T
is the total concentration of the particles
in the reactor and when modeling the discharge, we
averaged the temperature and particle concentration
on the assumption of the specified (Bessel) profiles of
the radial distribution of these parameters.
Electrical Parameters and the Plasma Composition
in HCl–H
2
Mixtures
A. M. Efremov*, A. V. Yudina, and V. I. Svettsov
Ivanovo State University of Chemistry and Technology, pr. F. Engel’sa 7, Ivanovo, 153000 Russia
*email: efreniv@usust.ru
Received June 9, 2011
Abstract
—The influence of the initial composition of an
HCl–H
2
mixture on the steadystate parameters
and composition of a dc glow discharge plasma (
p
= 40–200 Pa,
i
p
= 15–35 mA) is investigated. The calcu
lated data on the electron energy distributions, integral characteristics of the electron gas, and plasma com
position are gathered. It is shown that the dilution of HCl with hydrogen is not accompanied by a noticeable
variation either in the efficiency of processes under the electron impact or in the intensity of the ion bom
bardment of the surface in contact with the plasma.
DOI:
10.1134/S1063739711060059
LOWTEMPERATURE PLASMA DIAGNOSTICS
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