1063-7397/04/3303- © 2004 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 33, No. 3, 2004, pp. 169–182. Translated from Mikroelektronika, Vol. 33, No. 3, 2004, pp. 209–224.
Original Russian Text Copyright © 2004 by Kazanskii, V. Kolpakov, A. Kolpakov.
Anisotropic dry etching is extensively employed in
microelectronics and diffractive optics. In the former
ﬁeld, it is used for making vertical-walled diffusion
windows that provide abrupt pn junctions, thus reduc-
ing cross coupling . Vertical-walled etch proﬁles are
also important in diffractive optics . Reviews of
anisotropic dry etching are given in [3–8].
At the same time, it should be pointed out that reac-
tor designs and plasma-generation methods in common
use suffer from serious drawbacks:
(i) Plasma particles contaminate the surfaces of the
wafer, ﬁxtures, and work chamber .
(ii) The wafer surface is also contaminated by cath-
(iii) The plasma parameters vary with process con-
ditions, so that the etch rate is not uniform over the
wafer surface; this is known as the loading effect .
(iv) It is not possible to process a number of wafers
(v) Process equipment tends to be too complex and
bulky, and reactor designs are poorly compatible with
each other in terms of process conditions; these factors
hinder integration .
(vi) Plasma processes are power-consuming and use
expensive gases; hence high cost of ﬁnished product.
The above problems could be solved by using a
plasma stream satisfying the following conditions:
(i) The electrodes should be outside the plasma region.
(ii) The charged and reactive plasma species should not
strike the chamber sidewalls. (iii) The plasma stream
should be uniform in transverse directions. It is also
desired to reduce the complexity, dimensions, mass,
cost, and power consumption of plasma sources. Fur-
thermore, these should be compatible with any type of
vacuum machine in industrial use.
Published results suggest that the requirements may
be met by high-voltage gas-discharge (HVGD) plasma
sources [9–12]. In particular, Kolpakov  has shown
that HVGD is in principle suitable for plasma etching
(PE) and reactive ion etching (RIE). At the same time,
we are unaware of current reports in which the mecha-
nism of anisotropic HVGD etching is explored in a
The aim of this work was to experimentally investi-
gate and evaluate anisotropic HVGD etching of SiO
material widely used in microelectronics and diffrac-
tive optics. The process was also applied to some other
The HVGD etching of SiO
ﬁlms was carried out in
a UVN-2M-1 vacuum evaporator supplemented with
an HVGD plasma source designed for a wafer of diam-
eter 200 mm, as shown in Fig. 1. Having a grid anode,
the source generates plasma jets with a particle energy
of up to 6 keV and a current variable from 0 to 140 mA,
with the voltage adjustable over the range 0.3–6 kV.
The cathode is made of aluminum in order to enhance
emission. The plasma source is so small that the evapo-
rator can accommodate four such units operated simul-
taneously. The process gas is CF
or a CF
Prior to ﬁring, the work chamber is pumped down to
torr, and process gas is allowed to ﬂow into
the chamber until the pressure reaches 10
On applying an operating voltage to the cathode, a
plasma jet directed toward the wafer is produced down-
Anisotropic Etching of SiO
in High-Voltage Gas-Discharge Plasmas
N. L. Kazanskii*, V. A. Kolpakov*, and A. I. Kolpakov**
*Image Processing Systems Institute, Russian Academy of Sciences, Russia
**Korolev State Aerospace University, Samara, Russia
Received October 12, 2003
—An experiment is reported on anisotropic etching in a CF
plasma produced by high-voltage gas
discharge. The process is applied to SiO
and is also effected on SiC, Si, C (diamond), and As
. It is shown
that the etch rate is mainly dependent on the oxygen percentage, plasma parameters, and the wafer temperature.
It is established that etch rate is maximal at oxygen percentages of 0.8–1.5%, discharge currents of 80–140 mA,
and wafer temperatures of 390–440 K. The etching is found to be uniform within 1%.