1063-7397/04/3306- © 2004 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 33, No. 6, 2004, pp. 342–349. Translated from Mikroelektronika, Vol. 33, No. 6, 2004, pp. 419–428.
Original Russian Text Copyright © 2004 by Volk, Gornev, Novikov, Ozerin, Plotnikov, Rakov.
The scanning electron microscope (SEM) is often
used in linear measurements [1–5], for which purpose
precision techniques have recently been developed
6]. At the same time, some calibration issues have
yet to be resolved. Current practices presuppose that the
magniﬁcation and beam diameter remain unchanged in
proceeding from calibration to measurement [4, 7]
despite the fact that replacing a standard with a speci-
men entails altering the parameters.
The beam-diameter issue was addressed by
[7–9]. Those studies have yielded prac-
tical methods of image focusing that should be fol-
lowed in measurements in order to minimize errors
related to beam diameter.
The present study is concerned with the magniﬁca-
tion issue. This may be seen as having two facets. One
of them is how to measure feature sizes with the same
magniﬁcation that has been set in calibration. The sec-
ond facet is how to change magniﬁcation if, e.g., the
specimen turns out to be too large to ﬁt in an image with
the preset magniﬁcation.
Below we propose a solution to the problem of
changing SEM magniﬁcation in proceeding from cali-
bration to measurement.
2. THEORETICAL FRAMEWORK
The problem of magniﬁcation calibration may be
solved by means of an entity that would be directly
related to the magniﬁcation but would not depend on
the beam diameter, linear standards, or specimens. The
independence of the beam diameter is essential because
changing magniﬁcation entails adjusting beam diame-
ter. Note also that it is not possible to check whether
beam diameter remains the same on a specimen, and
the video waveform obtained from any surface is very
sensitive to beam diameter .
An entity that meets the above requirements is the
reference marker displayed on the screen of an SEM.
2.1 Traditional Use
of the Reference Marker
be the length of the reference marker on the
be the true length represented by the marker,
be the length represented by the marker as
declared by the manufacturer of the SEM (
indicated on the screen). In what follows,
be referred to as the true effective length and the
declared effective length, respectively.
vary with magniﬁcation, and
also related to the scanning range
and other SEM
parameters. If imaging satisﬁes the condition
is the magniﬁcation, then the marker can serve
as a linear standard that enables one to measure the
magniﬁcation at any
. In this case, it is possible to
properly measure the linear dimensions of a specimen.
Unfortunately, it is almost impossible to satisfy con-
dition (1), a conclusion supported by an enormous
number of experiments by many workers and with
many types of SEM. For this reason the marker is cur-
rently used for estimation rather than accurate measure-
ment. The latter is performed only after magniﬁcation
calibration [4, 6, 8] with special linear standards [3, 4,
6, 8, 10]. However, magniﬁcation calibration also has
some inherent drawbacks (see above). This fact stimu-
lates search for novel ways of using the marker as a lin-
ear standard. They must include calibration of the
marker, i.e., experimental identiﬁcation of the relation-
SEM Linear Measurement in a Wide Magnification Range
Ch. P. Volk*, E. S. Gornev*, Yu. A. Novikov**, Yu. V. Ozerin*,
Yu. I. Plotnikov*, and A. V. Rakov**
*OAO NIIME and Mikron Fabrication Plant, Moscow, Russia
**Natural Sciences Research Center, Institute of General Physics, Russian Academy of Sciences, Moscow, Russia
Received July 15, 2003
—A method of SEM linear measurement is proposed in which the reference marker displayed on the
screen is used as a standard. The method works in a wide range of magniﬁcation without magniﬁcation calibra-
tion. Calibration of the marker against the MShPS-2.0K linear standard is described. The characteristics of the
marker are investigated as functions of scanning range and declared effective marker length for the CamScan
S-4 model of SEM. The maximum allowable calibration interval is determined for this SEM.
MATERIALS AND MICROSTRUCTURE