Thermal microscope imaging system for semiconductor device
and IC invalidation analysis
GAO Meijinga,b JIN Weiqi a CHEN Yinana WANG Xia a
Department of Optical Engineering, Beijing Institute of Technology, Beijing 100081
Optoelectronic Department , Yanshan University, Qin Huangdao, Hebei province, 066004
In order to analyze the invalidation of the Semiconductor Device and IC, we proposed a novel digital thermal microscope
based on the uncooled focal plane detector. We give the operating principle, system’s construction and the mathematical
mode of noise equivalent temperature difference（NETD）.Based on the mathematical model, some measures were taken
to increase the system temperature resolution. Furthermore we proposed an adaptive nonuniformity correction algorithm
for the UFPA. The software for the thermal microscope is provided based on Visual C++. Results of real thermal image
experiments have shown that the digital thermal microscope is designed successfully and achieves good performance.
Thus it will become an effective means for invalidation Analysis. This method is a novel and unique contribution to field
of semiconductor device and IC invalidation analysis.
Keywords: invalidation analysis, digital thermal microscope, uncooled focal plane detector
Semiconductor Device and IC plays an increasingly role in recent years. The reliability of the Semiconductor Device and
IC is very important in the industry, and the performance of them can influence the whole system. So it is important to
test or make invalidation analysis for them. Unfortunately, testing for them is difficult. Since the electrical
interconnections are often only a few microns in width, physical contact with them for test purposes is not only difficult,
but is also dangerous to their mechanical and electrical integrity. Consequently, in most instances, only input and output
measurements are obtainable through the use of conventional test equipment. In the case of complex integrated circuitry,
this is inadequate, because it does not give information about the performance of the individual elements of the network.
For instance, the poor performance of one element could go undetected because of the compensating effect of another
element. Furthmore, several design or manufacturing defects that may eventually cause a failure are not detectable by
conventional testing. As a result, the nondestructive testing such as X-ray and ultrasonic were developed in recent years.
Few industrial functions have undergone so many significant technological changes in the last few years as has
nondestructive testing. In the test area, a new approach –infrared testing –is being developed as a promising technique
capable of yielding large amounts of information on thermal and electromechanical parameters affecting reliability that
conventional test equipment and methods are not capable of measuring. Since IR thermal imaging can gather
comprehensive temperature data from many points quickly and relatively accurately, it is well suited for PCB. Many
International Symposium on Photoelectronic Detection and Imaging 2007:
Photoelectronic Imaging and Detection, edited by Liwei Zhou, Proc. of SPIE Vol. 6621, 662117, (2008)
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Proc. of SPIE Vol. 6621 662117-1
hours and a lot of labor if thermocouples were used on the other hand, thermal imaging shows all details in a matter of
There are many infrared testing methods are used to analyze them. The TIP- I Electronic Circuit Fault Tester was
developed to detect and isolate electronic circuit fault nonintrusively, effectively and simply, which made up the short
coming of traditional methods and the thermal image of circuits could be applied in fault diagnosis easily. In addition to
that, there are some infrared systems for testing in our country. However, there are some disadvantages. These systems
are not microscope pattern, and the spatial resolution is low. As a result, some minute invalidation can not be found by
the infrared system. Although infrared microscope has not been produced in China, there are some infrared microscopes
in other countries.
An infrared microscope InfraScope III quickly, non-destructively, and without contact or liquid preparations, accurately
depicts a thermal image of your gallium arsenide or silicon circuit. The InfraScope III automatically corrects spatial
emissive variations on the device being tested, with an independent correction at every pixel. Figure 1 is the photo of the
InfraScope III and Figure 2 is the PCB and fuse thermal microscope images from the InfraScope III.
Another thermal microscope, the TVS-8000 has been jointly developed by Cincinnati Electronics Corporation and
Nippon Avionics Company, Ltd (Avio) of Japan. This unique system offers the user a wide variety of options for real
time display, analysis, and recording of thermal scenes.
However, most of the previous thermal microscopes have used cooled focal plane arrays (FPA). The cooled focal
plane detector is expensive and the refrigeration plant is big, so the application in our country is few, especially in the
field of testing and analysis for semiconductor and IC. In contrast, Uncooled focal plane arrays (UFPA) infrared
imaging devices have advantages such as low cost, light weight, superior reliability and little maintenance. The
uncooled focal plane arrays (UFPA) technology has been developing rapidly in recent years. However, the thermal
microscope based on UFPA has not been reported.
Figure 1: The Infrascope III Figure 2: The PCB and fuse thermal microscope imaging
Motivated by these, based on uncooled focal plane detector, we proposed a novel nondestructive digital thermal
microscope to analyze the invalidation of the semiconductor and IC. With the digital thermal microscope, you can
quickly evaluate thermal behavior of semiconductors, hybrid circuits and multi chip modules of incredibly small size.
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The system designed by us work quickly and accurately. The time and labor savings for real time, 2D graphical thermal
analysis are considerable. Furthermore it can measure temperatures in real time, non-destructively, without contact and
without cooling system.
We give the operating principle, system’s construction and the mathematical mode of noise equivalent temperature
difference （NETD）. Based on the mathematical model, some measures were taken to increase the system temperature
resolution. Furthermore we proposed an adaptive nonuniformity correction algorithm for the UFPA. The software for the
thermal microscope is provided based on Visual C++. In addition, some result and discussion will be given in this paper.
The novelty of our method is the application of uncooled focal plane detector in the thermal microscope, the construction
of the system, the software of imaging capturing and image processing based on Visual C++.
2. OPERATING PRINCIPLE
Anything will emit energy in the form of electromagnetic when it’s temperature is above absolute zero. And the
radioactive energy includes various wave lengths. And the wave length between 0.76～1 000 microns is infrared light
wave. It is known that infrared light has powerful thermometric effect and as a result it is fit for radiation thermometry.
The radiation thermometry is based on the Planck distribution law:
c1 λ −5
E bλ = (1)
exp[c 2 (λT )] − 1
E bλ -blackbody spectral radiant energy density, Wcm −2 µm −1
c1 -the first radiation constant, c1 = 3.7415 × 10 −12 W cm 2
c2 -the second radiation constant, c2 = 1.43879 cm K
λ -spectral radiant wavelength, µm
T-the absolute temperature of blackbody, K
With the Joule-Lenz’s law, wherever electrical current flows, a fraction of it turns into heat. This is generally called
power dissipation and result in a temperature rise of the element through which the current flows. This thermal rise
increases the power of the infrared radiation emitted by the surface of the element, and in turn this variation can be
measured by an adequate infrared detector. Thus, a direct correlation can be established between the electrical power
dissipation of an electronic part of a given design and the infrared radiation emitted by it, this correlation is the key to
the infrared evaluation of electrically energized microelectronic circuits. Thus the thermal microscope gets the circuit
thermal image. If the element gets out of order, the thermal imaging is different from the normal thermal imaging.
Proc. of SPIE Vol. 6621 662117-3
Consequently the fault location can be found with nondestructive method and then we complete the invalidation
3. THE CONSTRUCTION OF THE THERMAL MICROSCOPE
The thermal microscope is composed of special infrared microscopic objective, uncooled focal plane array mount,
imaging collector, the nonuniformity correction modular, image processor, imaging analyzing and processing system,
thermal microscope supporter and source of power.
The thermal microscopic objective is used to imaging the infrared radiation emitted by the surface of the element on the
uncooled focal plane arraymount. Large than normal optics with several unique properties were deliberately chosen for
infrared microscope. The detector aperture requirements dictated the use of a magnifying system: 2×、1.84×， ×和 1.44×
system was used, And the object aperture size is 0.24, the focal length is 66mm, and the field of view isφ9 and
Figure 3 is the photo of the infrared microscope object lens.
Figure 3: The photo of the thermal microscope object lens
With the uncooled focal plane array mount, the infrared radiation image is changed into the electron image. The size of
the UFPA is 320×240 pixels. And the working waveband is between 8 to 12µm, and the image surface is φ18
The image collector inverts the thermal electronic image into the digital image. In order to reducing the system volume,
the image collector is a portable collector with the USB interface card. It is known that sensitivity of the uncooled focal
plane array of is low. As a result, the thermal microscope imaging has many striping noise. The new adaptive
nonuniformity correction modular is used to delete the striping noise. The thermal microscopic image processing system
completes the display, analysis, storage and other processing. The thermal microscope supporter is for the thermal
microscope system integration and the source of power supplys the power for the whole system. And the circuit or object
can be retained on the top of four small bearers, and the bearers can be moved on the platform. In order to improve the
whole system’s performance. We designed some other mechanical parts for the system. Figure 4 shows the block
diagram of the digital thermal microscope and Figure 5 is the photo of the digital thermal microscope.
Proc. of SPIE Vol. 6621 662117-4
microscopical and Display Printer
Figure 4: The block diagram of the digital thermal microscope
Figure 5: The photo of the digital thermal microscope.
Since the smallest elements of an integrated circuit are the junctions which can be only a few microns wide, the area
resolution of an adequate infrared system should be able to view them. An even finer resolution capability might be
4.THE MATHEMATICAL MODEL OF NETD
Based on radiometry and the performance of the detector, the mathematical mode of NETD was established for the
thermal microscope. And the mathematical model can provide the foundation for system design and optimization. Figure
6 is the ray path of the micro thermal imaging
u0 u1 E
ds 0 ds
l l ′
Figure 6: The ray path of the thermal microscope imaging
After the complex derivation, we get the NETD for the thermal microscope is
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∆f n 4l ′2
NETD = (1 + ), (2)
Ad WT (TB )τ 0 D02
λ2 ∂M 0 (λ , T )
Where WT (T ) = ∫ D* (λ ) dλ
Considering the numerical aperture of the image field NA′=sin (u1), substituting NA′=sin (u1) into (1), we get
∆f n 1
NETD = . (3)
Ad WT (TB )τ 0 NA′2
It is just the NETD general expression of the thermal microscope. Under some conditions, the expression can be
simplified. From the equation, we can see that reducing the frequency can decrease the NETD. So, we can improve the
temperature resolution with the approach of frame addition.
5. THE ADAPTIVE NONUNIFORMITY CORRECTION MODULAR
The UFPA has inherent non-uniformities, e.g. the UFPA suffers from the vertical and horizontal striping fixed pattern
noise (FPN), especially for the vertical striping fixed pattern noise, which severely degrades the system performance and
can hardly be removed cleanly by many scene-based nonuniformity correction methods.
The simplest calibration methods assume a linear relationship between the detector signal and the target's temperature or
radiance. In reality, however, this relationship is complex and may require more sophisticated calibration approaches.
To cope with this problem, a new adaptive nonuniformity correction algorithm is proposed, which can complete NUC
with only one frame successfully.
The application results were shown in Figure 7 and Figure 7 a) is the raw thermal image of dime in China. It was obvious
that there is a great deal of striping noise remained. In contrast，The final corrected image is displayed as Figure 7 b),
apparently all striping artifacts are effectively removed and the original resolution is remained. Initial results of our
thermal microscope have proved that NUC can weaken striping noise greatly.
Figure 7: Thermal images of dime in China
With the nonuniformity correction modular, the thermal microscope system has reached the level of practical application.
Proc. of SPIE Vol. 6621 662117-6
In order to examine availability of the whole system, the LED circuit is applied into the experiment. Figure 8 is the photo
of the LED circuit and dime in China. From the photo we can see that the LED circuit is small. Figure 9 is thermal
microscope image of the LED circuit. We can see the double “s” figure in the centre of the LED circuit form the right
photo clearly, but we can’t see them in the left figure, and the stripping noise is clearly removed. Results indicate that
our system is designed successfully.
6. THE VISUAL C++ DIGITAL THERMAL MICROSCOPE SYSTEM
Figure 8: The photo of the LED circuit Figure 9: The thermal microscope image of the LED circuit
Based on the proposed approach and Visual C++, the thermal microscope software has been developed. The software
includes functions of imaging capturing, nonuniformity correction and imaging enhancement. The software of imaging
capturing and real time image processing based on Visual C++ makes the system more easily and practical.
RESULTS AND DISCUSSION
In order to analyze the Semiconductor Device and IC, we proposed a novel digital thermal microscope based on the
uncooled focal plane detector. The system’s construction, the detection principle, the component of hardware, the
mathematical modes of NETD and the adaptive nonuniformity correction for the UFPA and software for the system were
introduced in this thesis.
With the digital thermal microscope designed, minute sized thermal analysis can be achieved. Thus it will become an
effective means for invalidation Analysis. The system is very meaningful for academic analysis and is promising for
practical applications. This method is a novel and unique contribution to the field of semiconductor device and IC
invalidation analysis. The application of the system designed has turned out the availability of the system. And the
designed system can improve the field of the Semiconductor Device and IC. Furthmore the system can be used in the
field of biomedical and MEMS.
There are still some problems to be resolved such as the low area resolution. So further studies should be done to im
-prove the spatial resolution. And high-resolution imaging may be obtained under the conditions of low-level detectors. Next,
we will study the optical micro-scanning technique to expand the digital and analog processing capabilities of the system.
Authors would like to acknowledge for the support of BEIJING DALI macro source scientific technical incorporated
Proc. of SPIE Vol. 6621 662117-7
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