1063-7397/05/3404- © 2005 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 34, No. 4, 2005, pp. 210–216. Translated from Mikroelektronika, Vol. 34, No. 4, 2005, pp. 251–259.
Original Russian Text Copyright © 2005 by Petrin.
Low-pressure microwave plasma reactors are
widely used for surface treatment and ﬁlm deposition in
microelectronics . However, decreasing the chamber
pressure leads to enhanced electron diffusion from the
plasma to the walls, so that the problem arises of how
to maintain the electron density at a level required for
the applications .
The electron escape is commonly reduced by means
of magnetic traps. In a magnetic ﬁeld, transverse elec-
tron diffusion is caused by collisions with neutrals and
ions and so is less intense at lower pressures [3, 4].
Magnetic traps often employ electromagnets because
these allow one to easily adjust the magnetic ﬁeld and
trap parameters [5–7]. On the other hand, such designs
are rather cumbersome, requiring a high-power current
source and, usually, water cooling. An alternative
approach is to use strong permanent magnets [6, 7].
Such traps are preferable in many cases as no current
source is required. Moreover, permanent magnets allow
one to build distributed plasma sources for uniform pro-
cessing of large areas [8, 9].
Thus, the main problem with magnetic-trap micro-
wave reactors is how to heat the conﬁned electrons
while preventing their escape. As we shall show,
intense electron heating occurs in the regions of elec-
tron cyclotron resonance (ECR), i.e., where the cyclo-
tron frequency of electrons is close to the applied
In this study the mechanism of ECR heating is ﬁrst
investigated by computer simulation of electron motion
in a permanent-magnet trap. The simulation results
serve to deﬁne basic requirements on microwave
sources and magnets. As an illustration, we show how
this strategy can improve the design of a particular
Electron Cyclotron Resonance Used in Low-Pressure Microwave
Plasma Reactors with Permanent Magnets
A. B. Petrin
Institute for High Energy Density, Russian Academy of Sciences, Russia
Received August 24, 2004
—Methods are discussed for sustaining low-pressure microwave plasmas in which ionization is by
high-energy electrons conﬁned to permanent-magnet traps. Regions of electron cyclotron resonance are con-
sidered, which play a key role in wave–electron coupling. The results are presented of a computer simulation
of electron heating in a permanent-magnet trap. Against this background, basic requirements are set out con-
cerning the design of such plasma reactors.
Electron trap formed by two magnetic dipoles.