ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 9, pp. 1509!1514. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + I.L. Baranov, L.V. Tabulina, L.S. Stanovaya, T.G. Rusal’skaya, Yu.A. Shostak, 2007, published in Zhurnal Prikladnoi Khimii,
2007, Vol. 80, No. 9, pp. 1473!1478.
AND CORROSION PROTECTION OF METALS
Specific Features of Synthesis, Chemical Composition,
and Thermal Stability of Anodic Borosilicate Coatings
I. L. Baranov, L. V. Tabulina, L. S. Stanovaya, T. G. Rusal’skaya, and Yu. A. Shostak
Belarussian State University of Informatics and Radioelectronics, Educational Institution, Minsk, Belarus
Received October 3, 2006; in final form, January 2007
Abstract-Thickness and resistivity of anodic borosilicate coatings synthesized on n-type silicon were studied
in relation to the conditions in which the final forming potentials are reached and to the content of boric acid
in an ethylene glycol solution. A method for synthesis of the coatings for use in nanoelectronics was suggested
on the basis of data on the thermal stability of their chemical composition.
The development of the modern technology of
integrated circuits (ICs) is based on use of nanosize
intercomponent connections for their fabrication .
This brings up an urgent demand for diminishing
the smearing of the structural profiles formed in ICs.
A promising solution of this problem is use of elec-
trochemical methods for obtaining layers with re-
quired properties on the surface of semiconducting
silicon. In particular, oxide coatings doped with phos-
phorus- or boron-containing impurities can be syn-
thesized by anodic oxidation of silicon in ethylene
glycol solutions containing phosphoric or boric acid
. It has been suggested to use films of this kind
in the IC technology as thin-film diffusion sources
serving to form diode regions with improved switch-
ing characteristics in semiconducting silicon.
The advantages of the electrochemical method for
synthesis of such diffusion sources, compared to the
conventional high-temperature methods, consist in
that it is performed at room temperature and the
dopant content can be controlled by varying the com-
position of the electrolytic solution, and the film
thickness in the course of growth, by changing the
forming voltage [4, 5]. This method requires equip-
ment that is simple in design and convenient in use.
Because, in addition, the electrochemical method is
based on passing electric current through the semi-
conductor silicon regions being treated, this provides a
highly local transformation of their surface properties.
For this reason, it has been suggested to perform
selective anodic treatment of thermal silicon oxide
layers in order to change their dielectric properties by
varying the applied voltage [6, 7]. A particular advant-
age of the electrochemical method for synthesis of
anodic silicon coatings is that it uses low-cost and
environmentally safe reagents.
However, despite the indubitable process advant-
ages, this method has not been used in the IC tech-
nology so far. The main reason is that the dopant dis-
tribution in the forming oxide coatings over the sur-
face of semiconducting silicon is nonuniform. Re-
moval of such coatings after diffusion doping of the
starting silicon substrate gives rise to traces of erosion
on the surface of the starting material. This adversely
affects the electrical characteristics of p!n junctions.
This effect is particularly pronounced in the case of
diffusion sources based on anodic borosilicate coat-
ings, whose structure shows increased friability [2,
To eliminate this effect, it has been suggested to
use nitrate ethylene glycol solutions containing nitric
acid as a current-conducting additive and a mixture of
boric and arsenic acids (H
ratio 5 : 0.002) as dopant . However, the electrolyt-
ic solution suggested is characterized by increased
toxicity because of the use of arsenic acid, which is
a noxious substance, and by the formation of ex-
plosive ethylene glycol nitrate in preparation of this
solution from ethylene glycol and nitric acid .
This study is concerned with specific features of
synthesis of anodic borosilicate (ABS) coatings on