ISSN 10637397, Russian Microelectronics, 2014, Vol. 43, No. 1, pp. 15–20. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © I.I. Bobrinetskii, V.K. Nevolin, K.A. Tsarik, A.A. Chudinov, 2014, published in Mikroelektronika, 2014, Vol. 43, No. 1, pp. 23–28.
The focused ionbeam (FIB) lithography is one of
the basic methods for creating nanodimensional pat
terns with a resolution up to 10 nm, having found
applications for designing different units and ele
ments. The output of this method is low, restricting
commercial use of this technology. The FIB is basi
cally used for the reconstruction of photomasks for
EUV lithography and creation of masterdies for
nanoimprint lithography (NIL).
One of the new lithography methods uses gallium
for forming masks directly on silicon . By using the
FIB it is possible to form nanodimensional gallium
doped regions in the nearsurface silicon substrate
layer, forming specified patterns of required elements.
The advantages of nanodimensional ion doping
enable us to obtain precision formations of profiles of
semiconductor instrument structures due to the possi
bility of controlling the precision dose by changing the
exposure time and accelerating voltage. Similar con
trol accuracy ensures the high resolution of the formed
nm) without recourse to a polymer for pat
tern transfer . The high efficiency of focused ion
beam systems enables a high throughput of the nano
lithography process in electronics. The combination
of the doping process and other manufacturing crystal
surface treatment processes and the capability of cre
ating virtually any distribution profiles due to step
doping open broad prospects for this technology, e.g.,
when 3D patterns are formed by volumetric masking.
The removal of these masks is a laborconsuming
problem since gallium atoms are implanted into sili
con, and destruction and changes caused by implanted
ions in silicon have not been sufficiently studied.
A great number of regulating parameters of the ion
doping process (dose, type, ion energy, etc.) allows
one within wide limits to change the properties of the
doped layers but, along with this fact, requires a deep
physical understanding of ion implantation processes,
their behavior in the crystal lattice, the kinetics of the
formation and elimination of radiationinduced
defects, being necessary for highquality technological
modeling and the final efficient implementation of
instrument structures and integrated circuits.
The characteristics of gallium ion implantation in
silicon for creating a nanodimensional topological
pattern were studied theoretically in this work. Ion
implantation parameters are necessary for evaluating
etching rates and determining nanostructure sizes.
ION DOPING MODEL
OF THE SILICON SUBSTRATE
The standard microelectronic technology implies
semiconductor doping with impurities for creating
different instrument structures by changing its electro
physical properties (type of electrical conduction, spe
cific resistance, and other characteristics). However,
local ion doping opens a possibility of forming a three
dimensional nanodimensional pattern by combining
FIB and plasmachemical etching (PCE) technologies.
Due to the difference in the etching rates of doped and
undoped silicon regions, a threedimensional object is
formed on silicon by the PCE technology.
The formed 3D nanodimensional pattern can be
used, e.g., as a die for nanoimprint lithography. The
sequence of nanostructure formation by FIB masking
is as follows. The FIB lithography forms on the silicon
surface a pattern, consisting of locally doped regions,
which are further used as a mask for plasmachemical
etching (PCE) (Fig. 1).
A possible reason why the plasmachemical etch
ing of silicon regions doped with
much slower than that of “pure” regions lies in the
A Distribution of Ga
Ions in a Silicon Substrate
for NanoDimensional Masking
I. I. Bobrinetskii, V. K. Nevolin, K. A. Tsarik, and A. A. Chudinov
National Research Institute MIET, Moscow, Russia
Received June 25, 2013
—A nanodimensional doping method of nearsurface silicon layers using the focused ion beam was
studied by software tools based on mathematical calculations of ion ranges in crystals. The sizes of local dop
ing regions and concentrations of impurity atoms as function of real process parameters of the nanodimen
sional exposure to the ion gallium beam are calculated. Theoretical boundaries of process doping parameters,
taking silicon sputtering into consideration are determined.