ISSN 1063-7397, Russian Microelectronics, 2007, Vol. 36, No. 6, pp. 409–414. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © Yu.P. Snitovsky, V.V. Nelaev, V.A. Efremov, 2007, published in Mikroelektronika, 2007, Vol. 36, No. 6, pp. 465–471.
A standard approach to the design of silicon bipolar
transistors evolved out of efforts to strike a balance
between their power-handling and frequency capabili-
ties [1, 2]. However, it appears to have reached its limit.
Aside from process-technology considerations, there
are reasons of a fundamental nature. First, upper limits
exist on the temperature and electric ﬁeld that the semi-
conductor materials employed can tolerate in operation
. One must consider the possibility of breakdown,
given that power dissipation and ﬁeld strength can
V/cm, respectively. Other
important factors include drift-velocity saturation and
the skin effect . As a result, output power falls as
with increasing frequency,
A need therefore exists to ﬁnd ways of improving
bipolar-transistor performance. One promising strategy
is the method of self-alignment, with the horizontal
dimensions and shape of the collector, base, and emitter
regions being ﬁxed [6, 7].
Calculations and measurements have revealed that
the common-emitter output characteristic is adversely
affected by the lateral parts of the emitter junction as
injection increases, with both the gain and the cutoff
frequency reduced .
Snitovsky [7, 8] has put forth a novel concept of the
bipolar transistor that utilizes lateral injection to
enhance the injection efﬁciency. With more carriers
injected into the base region, the transistor should show
better performance parameters and common-emitter
output characteristics [6, 7]. It should also become
more resistant to ionizing radiation [7, 9, 10].
He has further proposed that the distance from each
emitter junction to the collector junction be made equal
to the thickness of the active base region, each emitter
junction be provided with a uniform concentration gra-
dient, and the minimum depth of the inactive base
region be made comparable with the thickness of the
active one . The injection efﬁciency would be
improved by formation of a plane depletion edge near
the collector junction. The above conditions should also
make for higher power, efﬁciency, power gain, and cut-
From a manufacturing point of view, the main
advantages of the novel concept over the standard
approach are as follows:
(1) It does not require a process step in which an
emitter mask and a base mask are aligned.
(2) Implantation into the active and the inactive base
region is performed in one process step, through both
the oxide and the emitter windows in it, a procedure
that is called self-formation.
(3) The emitter windows are also used for implanta-
tion into the emitter region, which provides self-align-
ment and prevents deformation of the base region
beneath the emitter.
(4) The diffusion annealing of the base regions takes
place in argon, which raises the proportion of electri-
cally active dopant atoms, allowing one to lower the
(5) The annealing is performed at a reduced temper-
ature and therefore ends in a sharper doping proﬁle of
This paper reports on a two-dimensional computer
simulation in which advanced physical models were
used to represent the formation of a vertical bipolar-
transistor structure. A comparison is made between the
new and the standard approach in the context of a
New Approach to the Manufacturing of Power Microwave
Bipolar Transistors: A Computer Simulation
Yu. P. Snitovsky, V. V. Nelayev, and V. A. Efremov
Belarussian State University, Minsk, Belarus
Received March 13, 2007
—A new manufacturing technology for power microwave silicon npn transistors is evaluated by 2D
computer simulation in Silvaco’s SSUPREM4. It enables one to increase the effective emitter area, which
makes for better power-handling and frequency capabilities, radiation hardness, and common-emitter output
characteristics. Advantages of the new technology over the standard one are demonstrated.
PACS numbers: 85.40.-e