1063-7397/04/3306- © 2004 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 33, No. 6, 2004, pp. 350–352. Translated from Mikroelektronika, Vol. 33, No. 6, 2004, pp. 429–432.
Original Russian Text Copyright © 2004 by Yuryev, Kalinushkin, Lytkin, Lyapunov.
It has been reported that superlarge defects may
occur in B-doped Czochralski-grown Si single crys-
tals [1, 2]. They were observed by scanning laser
microscopy in the mid-wave infrared (MWIR) ,
by electron-beam-induced current analysis , and by
small-angle MWIR scattering . The resistivity of the
single crystals ranged between 1 and 20
The defects have been hypothetically associated
with growth cavities that are occasionally found in Czo-
chralski-grown Si ingots, reducing the yield . This
problem is encountered in the manufacture of inte-
grated circuits as well as solar cells. Regrettably, it has
not been possible to detect superlarge defects before
This paper reports an experiment on active infrared
(IR) imaging as a method of checking as-grown Si
ingots for superlarge defects (Fig. 1). The approach
proposed is simple and convenient. It is conceptually
the same as visual inspection of optical materials. Sili-
con ingots are transparent to IR radiation with wave-
lengths over 1.1
m. As-grown ingots have a smooth
lateral surface that does not seriously distort IR images.
Any suitably positioned uniformly heated body can
serve as the IR illuminator. The ingot can be rotated and
translated along its axis during inspection.
In fact, active IR imaging should also be suitable for
detecting bulk optical inhomogeneities caused by sufﬁ-
ciently large growth defects.
At the same time, the task places special require-
ments on the imager. First, its temperature sensitivity
should be as high as possible, 50–60 mK at least,
because it is this parameter that determines the resolu-
tion. Second, the imager should have a frame rate of
over 25 Hz so that it could work in real time. This ﬁgure
of merit determines the length of time necessary for
inspection. Third, the imager should be implemented as
an array of adequate size, 256
256 at least.
by Active IR Imaging
V. A. Yuryev*, V. P. Kalinushkin**, A. P. Lytkin***, and S. I. Lyapunov***
* Natural Science Center, Prokhorov Institute of General Physics, Russian Academy of Sciences, Moscow, Russia
** Prokhorov Institute of General Physics, Russian Academy of Sciences, Moscow, Russia
*** ZAO Matrichnye Tekhnologii, Moscow, Russia
e-mail: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Received July 15, 2003
t is demonstrated by experiment that active IR imaging can be used to detect internal inhomoge-
neities in silicon ingots, the IR illuminator being any uniformly heated body. The method proposed is concep-
tually the same as visual inspection of optical materials. It does not require any special preparation of ingots. It
is concluded that the simplicity of the method should make it convenient for the quality control of major semi-
conductor materials under production conditions.
MATERIALS AND MICROSTRUCTURE
Experimental arrangement: (
) IR illuminator, (
) test ingot, and (
) IR imager. The test ingot is a solar-cell multicrystalline
silicon ingot of diameter 200 mm. The IR illuminator is a uniformly heated body.