Optical Microscopy Lab Report
Eshita Gurung
Micro and Nano System Technology
University of South-Eastern Norway
Horten, Norway
230738@usn.no
Sharaban Tahora
Micro and Nano System Technology
University of South-Eastern Norway
Horten, Norway
230734@usn.no
Neda Ghiasi
Micro and Nano System Technology
University of South-Eastern Norway
Horten, Norway
230742@usn.no
Abit Babu
Micro and Nano System Technology
University of South-Eastern Norway
Horten, Norway
230736@usn.no
Samarbir Sing
Micro and Nano System Technology
University of South-Eastern Norway
Horten, Norway
230739@usn.no
Abstract: This essay reports the measurement of several
dimensions of a RF MEMS-switch using a Leica microscope.
Bright field, dark field mode, depth of focus, depth of field and
their relationship with resolution and numerical aperture are
discussed.
I.
INTRODUCTION
With the advent of technology, there has been an
enormous growth in the application of optical microscopy
for micron and submicron level investigations in a wide
variety of disciplines. Early microscopes were hindered
by optical aberration, blurred images, and poor lens
design but advances in digital imaging and analysis have
also enabled microscopes to acquire quantitative
measurements quickly and efficiently.
II.
IV.
RESULT & DISCUSSION
The smallest magnification of objective lens to view the
whole structure is 2.5x. Hence, total magnification will be
25x due to 10x magnification of the microscope lens and
the field of view is equal to 4574 x 3382 μm.
The microscopic image of the test pattern is displayed in
the below figure 1.
MATERIALS REQUIRED
Leica Optical Microscope
Sample pattern – RF switch
PC with Leica application suite
III.
METHODES
The sample pattern (RF Switch) was kept under the Leica
microscope and was adjusted in the correct position and
magnification. By adjusting the focus, a clear image of the
sample was obtained. After that, the sample pattern was
viewed in the ocular and in the Leica application suite in
the bright mode initially. In this mode sample roughness
could be reviewed. The lateral measurement/dimensions,
height differences, areas and angles of the sample pattern
were measured and the values were recorded. In order to
go over the details of edges, the sample was reviewed in
dark filed mode also.
Figure 1: Microscopic image of the test patter (RF switch)
Figure 2. Transversal cut of the MEMS structure portraying the
elements to be measured [2]
The values of the L1, L2, L3, V1, W1, W2, Z1 and Z2
which were measured with the help of Leica software are
tabulated below.
Figure 2b: Measurement of the length (L2) of the bridges in the
Microsystem
Table 1: Measurement values of the different cross section
of the RF switch
Sl.No
1
2
3
4
5
6
7
8
Structure
L1
L2
L3
V1
W1
W2
Z1
Z2
Measurement (μm)
284.254 μm
2482.498 μm
74.757 μm
46.469
77.701 μm
194.754 μm
1 μm
1 μm
In figure 2a and figure 2b measurement of length, withs
and angle of the bridges are illustrated.
Figure 2a: Measurement of the lengths (L1 & L3), widths
(W1 & W2) and angle(V1) of the bridges in the microsystem
Figure 2c: Measurement of Z1 and Z2 i.e. height difference
between the layers recorded with the depth of focus.
Dark Field Mode: It provides a higher contrast due to the
scattered light in order to observe defects and edges of the
test pattern. It also provides a sense of depth difference
not clearly visualized in bright field mode due to the
darker tone in the background at least for the
magnification observed in figure 3a. Dark filed mode
imaging
complements
the
optical
microscopy
observations when contamination and edge observation is
relevant.[3]
In comparison to the bright mode, dark field mode is
highly suitable to identify the edges, outlines, topography
and the surface defects on the sample. In figure 3a sample
defects are shown clearly. Damaged parts are viewed as
bright points or disturbed edges.
Relationship between the depth of focus and the
numerical aperture (NA)
Depth of focus is inversely proportional to numerical
aperture i.e
Dfocus=
Relationship between the resolution and NA
From the equation above, it is evident that “R”
(Resolution) is inversely proportional to the numerical
aperture, hence smaller features can be resolved with a
higher numerical aperture value.
Figure 3a: Microscopy image with dark field mode
V. CONCLUSION
This experiment can be concluded with the following
understanding that Leica optical microscope is an efficient
device to take the measurements of various samples but
the accuracy of the dimensions would be more accurate
with the automated process than to the manual process as
human error are prone to occur. The depth of Field and
depth of Focus for magnification of 100x and 2.5x
lenses, relationship between the depth of focus and the
numerical aperture and relationship between the
resolution and NA were discussed.
Figure 3b: Microscopy image with bright field mode
References
[1]
Depth of Field and Depth of Focus for 100x lens and
2.5x lens
As lower NA(Numerical aperture) increases the depth of
focus and depth of field hence both depth of field and
focus is higher for 2.5x lens in comparison to 100x lens as
it has lower numerical aperture i.e. NA = 0.07 and NA=
0.09 for 100x lens.[4]
where λ is the “Wavelength” and NA is the “Numerical
aperture”.
s=0.61
[2]
[3]
[4]
ScienceDirect."OpticalMicroscope."
https://www.sciencedirect.com/topics/engineering/opticalmicroscope
Measurement course lab shit
https://www.ruf.rice.edu/~bioslabs/methods/microscopy/dfield.htm
l
Microstructural Characterization of Materials - 2nd Edition
David Brandon and Wayne D. Kaplan © 2008 John Wiley &
Sons,Ltd. ISBN: 978-0-470-02784-4