- Email: [email protected]
Low power consumption micro C2H5OH gas sensor based on micro-heater and ink jetting technique
Accepted Manuscript Title: Low Power Consumption Micro C2 H5 OH Gas Sensor based on Micro-heater and Ink jetting Technique Author: S.E. Moon H.-K. Lee N-J. Choi H.T. Kang J. Lee S.D. Ahn S.Y. Kang PII: DOI: Reference:
S0925-4005(14)01244-1 http://dx.doi.org/doi:10.1016/j.snb.2014.10.034 SNB 17530
To appear in:
Sensors and Actuators B
Received date: Revised date: Accepted date:
16-6-2014 15-9-2014 8-10-2014
Please cite this article as: S.E. Moon, H.-K. Lee, N.-J. Choi, H.T. Kang, J. Lee, S.D. Ahn, S.Y. Kang, Low Power Consumption Micro C2 H5 OH Gas Sensor based on Micro-heater and Ink jetting Technique, Sensors and Actuators B: Chemical (2014), http://dx.doi.org/10.1016/j.snb.2014.10.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
IMCS 2014, paper ID: TPS-T1-16
Low Power Consumption Micro C2H5OH Gas Sensor based on Micro-heater and Ink
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jetting Technique
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S. E. Moon, H-K. Lee, N-J. Choi, H. T. Kang, J. Lee, S. D. Ahn, and S. Y. Kang
Phone: +82-42-860-5608
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E-mail: [email protected]
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FAX: +82-42-860-5603
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Corresponding author: Ph.D. S. E. Moon
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ETRI, 138 Gajeong-ro, Yuseong-gu, Dejeon 305-700, Korea
Address: 305-700, Convergence Components & Materials Research Laboratory, Electronics and Telecommunications Research Institute, 138, Gajeong-ro, Yuseong-Gu, Daejeon, South Korea
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IMCS 2014, paper ID: TPS-T1-16
Low Power Consumption Micro C2H5OH Gas Sensor based on Micro-heater and Ink jetting
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Technique
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S. E. Moon, H-K. Lee, N-J. Choi, H. T. Kang, J. Lee, S. D. Ahn, and S. Y. Kang
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ETRI, 138 Gajeong-ro, Yuseong-gu, Dejeon 305-700, Korea
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Abstract
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Micro alcohol gas sensor was fabricated based on micro-heater by using CMOS compatible MEMS process and ink jetting
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technique. The paste for ink jetting deposition was based on semiconducting In2O3 powder. In the structure of micro-heater,
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two semi-circled Pt heaters, where some etching holes including etching hole in the center of the micor-heater exist, are
connected to the spreader for thermal uniformity and reduction of the Si etching time. Based on the above design, low power
consumption alcohol gas sensor was fabricated, which showed substantial sensitivity down to 0.05 ppm alcohol at low power
consumption (24mW).
Keyword: gas sensor, In2O3, micro-heater, surface micromachining, alcohol
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IMCS 2014, paper ID: TPS-T1-16
1. Introduction Metal-oxide powders based chemiresistive gas sensors have been applied to various fields with other technologies to
detect
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inflammable, toxic, and odorless gases, such as, H2, NO2, CO, NH3, and volatile organic chemicals (VOC), because of low cost,
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is needed in many fields; industrial, environmental and human monitoring [12-17].
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small size, measurement simplicity, ease of fabrication, and low detection limit [1-11]. Among them, alcohol detection sensor
Moreover to reduce the power consumption of the device, the micro-heater to enhance the sensing and desorption of the target
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gas has been normally adopted. Due to the difficulties in MEMS technique and higher production cost for micro gas sensor,
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few commercial devices are selling by pioneering company. This technology needs further improvement in handling device
wafer and sensor fabrication processes including packaging process [18-24].
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In this study we report surface micromachined gas sensors based on the In2O3 nano-powders and micro-heater, which show low power consumption and high sensitivity for alcohol detection. The fabrication process for the micro gas sensor was based
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on the conventional complementary metal semiconductor (CMOS) compatible micro electro mechanical systems (MEMS)
processes for mass-production, which is easy to integrate with other devices and electronic circuitry.
2. Experimentals Semiconducting In2O3 nano-powders were purchased from Advanced Nano Products Co., Ltd., Korea. The paste containing In2O3 particles was dispersed in water and washed with ethyl acetate or diethyl ether to give In2O3 ink for ink jetting.
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The bulk X-ray diffraction (XRD) analysis of the powder was carried out for the Bragg angle (2) from 10 to 60o using Cu K
about the particles size and shape was obtained by using scanning electron microscope (SEM).
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radiations and the average grain size of the powder was calculated using Scherrer formula. In addition, further information
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To activate the gas sensing properties and to lessen the power consumption of the sensor, Si-based micro-heater was adapted,
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which was fabricated by using CMOS compatible MEMS processes. After micro-heater fabrication, metal oxide paste
including In2O3 nano-powders were deposited on the device by ink jetting technique and post-annealed by using the embedded
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micro-heater.
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Gas sensing properties were measured using a computer-controlled characterization system. The resistances of the sensor
materials upon the Si micromachined micro-heater were measured. The response, R, is given by the rate of change in the
air, respectively.
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resistance to the initial resistance, R = R/R0= |Rg-R0|/R0, where Rg and R0 are the resistance in the test gas and in humidified
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And the bridge deformation was measured by a three dimensional (3D) vibrometer with a variation of operating power and the
endurance of micro-heater with repetitive operation was tested by using DC power source and home-made switching set-up by PC control. The variation of micro-heater resistance, RHV, is given by the rate of change in the resistance to the initial resistance, RHV = RH/RH0 = |RH-RH0|/RH0, where RH and RH0 are the resistance of micro-heater before the repetition test and after the repetition test, respectively.
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3. Results and Discussion Fig. 1 (a) shows the XRD patterns of the In2O3 nano-powders. All peaks belong to cubic In2O3 phase. The calculated average
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grain size of the In2O3 nano-powders using Scherrer formula was 526 nm, which grain size was proper to detect gas as shown
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SEM image in Fig 1 (b).
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In the structure of the micro-heater, the lines of two semi-circular Pt heaters are connected to the power supply. The low power
consumption micro-heater was fabricated through a CMOS compatible MEMS processes, which was designed to endure high
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stress and to be suitable for ink jetting deposition [25]. By the way, there are some differences in the design and process, for
example, the shape of the etching holes was circular and the etching hole in the center of the micro-heater was added for short
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Si etching time and increasing mechanical stability. The process cost down for saving XeF2 gas usage and structural stability increase due to lower ething damage are subsidiary positive effects for adapting this design. The detailed fabrication processes
are shown in Fig. 2. The heating electrode and sensing electrode were chosen as Pt and Au/Pt, respectively, due to strong
thermal endurance and chemical endurance. All metal patterns except the area for sensing material deposition or wire bonding
were passivated to prevent deterioration by air and humidity, etc. After the dry Si etching process with XeF2 gas, sensing material deposition was done by using ink jetting technique. Because the sensing material deposition process was the last step
of the micro gas sensor fabrication processes and the sensing material post-annealing process can be done by using the
embedded micro-heater, mass-production and the integratation with other devices and electronic circuitry are more feasible
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and lower cost process.
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A photograph of the micro alcohol gas sensor based on metal oxide film is shown in the Fig. 3. In the left image of the micro gas sensor, about 50 m diameter donut shaped transparent sensing In2O3 film exists in the center of micro bridge with the
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circular shaped surface micromachined Si etching area with etching hole in the center of micro bridge, where heating element
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exists inside, which were fabricated based on 6 inch Si substrate, as shown in the right image of Fig. 3.
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Fig. 4 shows the result of a bridge depth profile and deformation for our sensor, which was measured by a 3D vibrometer. The
z-axis deformation map and bridge deformation depth profile across line aa’ of our sensor with about 60 mW DC power are shown in Fig. 4(a) and (b), where the donut shape sensing film with about 2 m thickness is located on the micro-heater in the center, which was thinner than that of screen printed sensing material as previous work [25]. As shown in Fig. 4(c), there is a deformation of about 4.5 m when no power is applied to the micro-heater, which was smaller than that of previous work because of the lighter sensing film weight and smaller micro-heater size. And the bridge is not bent over about 6.4 m even though the direct current (DC) power into the micro-heater is about 60 mW, which is larger than two times of the value of our
sensor operating power.
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As shown in Fig. 5, In2O3 nano-powders (generally n-type semiconductor) devices showed a conductance decrease at different
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concentrations of 0.05 to 1 ppm C2H5OH gas and the sensing response increased with an increasing C2H5OH concentration. The flow time of the target gas was 60 seconds, the response was nearly saturated for all the concentrations, and the initial
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resistance was recovered after the air gas was purged. The power consumption of the sensor was about 24 mW, which is much
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lower than that of the commercial semiconducting gas sensor and the previous work [25]. The sensor device showed response
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(R) values of about 0.2 and 0.53 for 0.1 and 1 ppm C2H5OH, respectively.
One of empirical phenomenological formula with flat-band condition, it is known that the formulae assumes the power law form, R = Κ pgα, wherein response R = ∆R/Ro, Κ is a reaction constant, pg is a gas concentration or a partial pressure, and α is an exponent between 0 and 1 [26-27]. For our sensor, which consists of In2O3 nano-powders, may satisfy the flat-band condition, and. the data from fitting with the aforementioned equation were Κ = 0.54 and α = 0.41, which are reasonable data
that can be easily found elsewhere, as shown in Fig. 6.
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The successive alcohol gas sensing properties for our sensor was confirmed, as shown in Fig. 7, where the alcohol
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concentration was 0.2 ppm and the target gas flow on and off time duration were about 30 and 40 sec, respectively. The curve
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shape of the ratio of the sensing resistance to the base resistance (Rg/R0) for the micro gas sensor with 24 mW power
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consumption was similar to each other and the sensing curve was fully saturated with target gas and fully recovered without
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target gas.
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With low power consumption, some test results for endurance characteristics of our sensor are shown in Fig. 8, the variation of the micro-heater resistance was measured for repetitive input pulse DC power for 2104 times. Applied successive input DC
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power pulse pattern into the micro-heater with 25 mW amplitude on for 1 s and off for 1 s. The variation of the normalized micro-heater resistance RHV after 2104 times repetition operation test are shown in Fig. 8, where the variation rate of the micro-heater resistance, RHV, is below 0.3% for 2104 times repetitive 25 mW pulse operations.
4. Summary
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Low power consumption and high sensitive micro C2H5OH gas sensor was fabricated based on micro-heater using In2O3 nanopowders, which was fabricated by using CMOS compatible MEMS process. Micro gas sensor showed substantial sensitivity
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down to 0.05 ppm alcohol at lower power consumption (24 mW) with respect to that of commercial product and high
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endurance.
Acknowledgements
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This work was supported by the Ministry of Trade, Industry and Energy 'Technology development project associated with
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commercialization and by the “Sensitivity touch platform development and new industrialization support program” through the
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Biographies
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Seung Eon Moon received the BS, MS, and PhD degree in Physics from Seoul National University, Seoul, Korea in 1990, 1994 and 2000, respectively. Since 2000, he has been working for Electronics and Telecommunications Research Institute (ETRI) in the area of various application devices based on oxide materials. His current research
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activities are the development of MEMS gas sensor, piezoelectric energy harvester, ferroelectric phase shifter and
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ferroelectric or oxide non-volatile memory.
Hyung-Kun Lee is a senior researcher of Components & Materials Research Laboratory at Electronics and Telecommunications Research Institute (ETRI) in South Korea. Prior to joining ETRI, he carried out postdoctoral
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experience in Center for Smart Supramolecules, Korea in 2004 and Materials Science and Engineering at Northwestern University, USA from 2005 until 2006. He completed Ph.D. in Chemistry from the Pohang University of Science and Technology (POSTECH) in 2004, studying self-assembly of soft materials such as liquid
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crystals and supramolecular vesicles. His current research interests are mainly focused on gas sensors and their applications in actuators.
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Nak-Jin Choi received his B.S. from Pukyong National University, Korea in 1996 and M.S. and Ph.D from Kyungpook National University in 1998 and 2005, respectively. Since 2005, he has been working for Electronics
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and Telecommunications Research Institute (ETRI) in the area of various application devices based on oxide polymer.
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materials. He has been involved with research on e-nose since 1997, and also conducted research on actuators by
Hyuntae Kang received his MS degree in Chemistry from Pusan National University in 2010. He is currently pursuing a Ph.D. degree under the supervision of K.H. Park. His research interest is focused on the development of nanocatalysts for organic reaction and gas sensor. Jaewoo Lee received the B.S. degree in electrical and electronics engineering from Korea University, Seoul, Korea, in 2000, and the M.S. degree in information and communication engineering from Gwang-Ju Institute of Science and Technology (GIST), Gwangju, Korea, in 2002. After that, He joined a micro-system team at Electronics and Telecommunication Research Institute (ETRI), Daejeon, Korea. He focused on RF MEMS switches for the frontend Antenna module. Since 2006, he has developed MEMS microphones for mobile application. Seong Deok Ahn received his BS degree in Inorganic Materials Science & Engineering from Hanyang University, Seoul, Korea, in 1991, BS degree in Electronic Materials Science & Engineering from KAIST, Daejeon, Korea, in 1994, and PhD degree in Materials Science & Engineering from KAIST, Daejeon, Korea in 2000. He is
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currently a principal researcher at Components & Materials Research Laboratory in Electronics and Telecommunications Research Institute (ETRI). His current research activities are the development of touch sensors, haptic devices, flexible devices and disaplys, electronics papers and oxide TFT.
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Seong Yeol Kang received his BS degree in Physics from Seoul National University, Seoul, Korea, in 1988, BS degree and PhD in Physics from KAIST, Daejeon, Korea, in 1991 and 1994 respectively. He is currently a principal researcher at Components & Materials Research Laboratory in Electronics and Telecommunications Research
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Institute (ETRI). His current research activities are the development of touch sensors, haptic devices, flexible
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devices and disaplys, electronics papers and oxide TFT.
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20
30
40
2 (Degree)
50
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1k
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2k
(422)
(400)
3k
(440)
(a)
4k
0 10
10 μm
(a) XRD patterns and (b) SEM image of In2O3 nano-powders, which were deposited on Si substrate.
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Fig. 1.
(222)
5k
(b)
(211)
Intensity (A.U.)
6k
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Fabrication processes for C2H5OH gas sensor by using CMOS compatible MEMS process
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Fig. 2.
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Enlarged image of the C2H5OH sensor (left) and the gas sensor wafer (right).
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Fig. 3.
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(a)
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(b)
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(c)
Fig. 4. The results of (a) a sensor z-axis deformation map, (b) a bridge deformation depth profile with 70.5 mW applied power
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across line aa’ and (c) a bridge z-axis deformation as a function of operating power for our sensor measured by a 3D
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vibrometer.
Fig. 5.
C2H5OH gas sensing properties of the fabricated micro gas sensor with 24 mW power consumption.
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Gas-concentration-dependent sensing properties of micro gas sensor for 0.05-1 ppm C2H5OH gas.
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Fig. 6.
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Fig. 7.
Successive gas sensing properties of the fabricated micro gas sensor with 24 mW power consumption for 0.2 ppm C2H5OH.
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Fig. 8. The temporal drift observed on the micro-heater for repetitive DC power pulse operation.
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S0925-4005(14)01244-1 http://dx.doi.org/doi:10.1016/j.snb.2014.10.034 SNB 17530
To appear in:
Sensors and Actuators B
Received date: Revised date: Accepted date:
16-6-2014 15-9-2014 8-10-2014
Please cite this article as: S.E. Moon, H.-K. Lee, N.-J. Choi, H.T. Kang, J. Lee, S.D. Ahn, S.Y. Kang, Low Power Consumption Micro C2 H5 OH Gas Sensor based on Micro-heater and Ink jetting Technique, Sensors and Actuators B: Chemical (2014), http://dx.doi.org/10.1016/j.snb.2014.10.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
IMCS 2014, paper ID: TPS-T1-16
Low Power Consumption Micro C2H5OH Gas Sensor based on Micro-heater and Ink
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jetting Technique
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S. E. Moon, H-K. Lee, N-J. Choi, H. T. Kang, J. Lee, S. D. Ahn, and S. Y. Kang
Phone: +82-42-860-5608
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E-mail: [email protected]
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FAX: +82-42-860-5603
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Corresponding author: Ph.D. S. E. Moon
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ETRI, 138 Gajeong-ro, Yuseong-gu, Dejeon 305-700, Korea
Address: 305-700, Convergence Components & Materials Research Laboratory, Electronics and Telecommunications Research Institute, 138, Gajeong-ro, Yuseong-Gu, Daejeon, South Korea
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IMCS 2014, paper ID: TPS-T1-16
Low Power Consumption Micro C2H5OH Gas Sensor based on Micro-heater and Ink jetting
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Technique
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S. E. Moon, H-K. Lee, N-J. Choi, H. T. Kang, J. Lee, S. D. Ahn, and S. Y. Kang
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ETRI, 138 Gajeong-ro, Yuseong-gu, Dejeon 305-700, Korea
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Abstract
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Micro alcohol gas sensor was fabricated based on micro-heater by using CMOS compatible MEMS process and ink jetting
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technique. The paste for ink jetting deposition was based on semiconducting In2O3 powder. In the structure of micro-heater,
Ac ce p
two semi-circled Pt heaters, where some etching holes including etching hole in the center of the micor-heater exist, are
connected to the spreader for thermal uniformity and reduction of the Si etching time. Based on the above design, low power
consumption alcohol gas sensor was fabricated, which showed substantial sensitivity down to 0.05 ppm alcohol at low power
consumption (24mW).
Keyword: gas sensor, In2O3, micro-heater, surface micromachining, alcohol
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IMCS 2014, paper ID: TPS-T1-16
1. Introduction Metal-oxide powders based chemiresistive gas sensors have been applied to various fields with other technologies to
detect
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inflammable, toxic, and odorless gases, such as, H2, NO2, CO, NH3, and volatile organic chemicals (VOC), because of low cost,
us
is needed in many fields; industrial, environmental and human monitoring [12-17].
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small size, measurement simplicity, ease of fabrication, and low detection limit [1-11]. Among them, alcohol detection sensor
Moreover to reduce the power consumption of the device, the micro-heater to enhance the sensing and desorption of the target
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gas has been normally adopted. Due to the difficulties in MEMS technique and higher production cost for micro gas sensor,
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few commercial devices are selling by pioneering company. This technology needs further improvement in handling device
wafer and sensor fabrication processes including packaging process [18-24].
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In this study we report surface micromachined gas sensors based on the In2O3 nano-powders and micro-heater, which show low power consumption and high sensitivity for alcohol detection. The fabrication process for the micro gas sensor was based
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on the conventional complementary metal semiconductor (CMOS) compatible micro electro mechanical systems (MEMS)
processes for mass-production, which is easy to integrate with other devices and electronic circuitry.
2. Experimentals Semiconducting In2O3 nano-powders were purchased from Advanced Nano Products Co., Ltd., Korea. The paste containing In2O3 particles was dispersed in water and washed with ethyl acetate or diethyl ether to give In2O3 ink for ink jetting.
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The bulk X-ray diffraction (XRD) analysis of the powder was carried out for the Bragg angle (2) from 10 to 60o using Cu K
about the particles size and shape was obtained by using scanning electron microscope (SEM).
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radiations and the average grain size of the powder was calculated using Scherrer formula. In addition, further information
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To activate the gas sensing properties and to lessen the power consumption of the sensor, Si-based micro-heater was adapted,
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which was fabricated by using CMOS compatible MEMS processes. After micro-heater fabrication, metal oxide paste
including In2O3 nano-powders were deposited on the device by ink jetting technique and post-annealed by using the embedded
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micro-heater.
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Gas sensing properties were measured using a computer-controlled characterization system. The resistances of the sensor
materials upon the Si micromachined micro-heater were measured. The response, R, is given by the rate of change in the
air, respectively.
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resistance to the initial resistance, R = R/R0= |Rg-R0|/R0, where Rg and R0 are the resistance in the test gas and in humidified
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And the bridge deformation was measured by a three dimensional (3D) vibrometer with a variation of operating power and the
endurance of micro-heater with repetitive operation was tested by using DC power source and home-made switching set-up by PC control. The variation of micro-heater resistance, RHV, is given by the rate of change in the resistance to the initial resistance, RHV = RH/RH0 = |RH-RH0|/RH0, where RH and RH0 are the resistance of micro-heater before the repetition test and after the repetition test, respectively.
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3. Results and Discussion Fig. 1 (a) shows the XRD patterns of the In2O3 nano-powders. All peaks belong to cubic In2O3 phase. The calculated average
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grain size of the In2O3 nano-powders using Scherrer formula was 526 nm, which grain size was proper to detect gas as shown
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SEM image in Fig 1 (b).
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In the structure of the micro-heater, the lines of two semi-circular Pt heaters are connected to the power supply. The low power
consumption micro-heater was fabricated through a CMOS compatible MEMS processes, which was designed to endure high
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stress and to be suitable for ink jetting deposition [25]. By the way, there are some differences in the design and process, for
example, the shape of the etching holes was circular and the etching hole in the center of the micro-heater was added for short
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Si etching time and increasing mechanical stability. The process cost down for saving XeF2 gas usage and structural stability increase due to lower ething damage are subsidiary positive effects for adapting this design. The detailed fabrication processes
are shown in Fig. 2. The heating electrode and sensing electrode were chosen as Pt and Au/Pt, respectively, due to strong
thermal endurance and chemical endurance. All metal patterns except the area for sensing material deposition or wire bonding
were passivated to prevent deterioration by air and humidity, etc. After the dry Si etching process with XeF2 gas, sensing material deposition was done by using ink jetting technique. Because the sensing material deposition process was the last step
of the micro gas sensor fabrication processes and the sensing material post-annealing process can be done by using the
embedded micro-heater, mass-production and the integratation with other devices and electronic circuitry are more feasible
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and lower cost process.
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A photograph of the micro alcohol gas sensor based on metal oxide film is shown in the Fig. 3. In the left image of the micro gas sensor, about 50 m diameter donut shaped transparent sensing In2O3 film exists in the center of micro bridge with the
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circular shaped surface micromachined Si etching area with etching hole in the center of micro bridge, where heating element
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exists inside, which were fabricated based on 6 inch Si substrate, as shown in the right image of Fig. 3.
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Fig. 4 shows the result of a bridge depth profile and deformation for our sensor, which was measured by a 3D vibrometer. The
z-axis deformation map and bridge deformation depth profile across line aa’ of our sensor with about 60 mW DC power are shown in Fig. 4(a) and (b), where the donut shape sensing film with about 2 m thickness is located on the micro-heater in the center, which was thinner than that of screen printed sensing material as previous work [25]. As shown in Fig. 4(c), there is a deformation of about 4.5 m when no power is applied to the micro-heater, which was smaller than that of previous work because of the lighter sensing film weight and smaller micro-heater size. And the bridge is not bent over about 6.4 m even though the direct current (DC) power into the micro-heater is about 60 mW, which is larger than two times of the value of our
sensor operating power.
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As shown in Fig. 5, In2O3 nano-powders (generally n-type semiconductor) devices showed a conductance decrease at different
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concentrations of 0.05 to 1 ppm C2H5OH gas and the sensing response increased with an increasing C2H5OH concentration. The flow time of the target gas was 60 seconds, the response was nearly saturated for all the concentrations, and the initial
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resistance was recovered after the air gas was purged. The power consumption of the sensor was about 24 mW, which is much
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lower than that of the commercial semiconducting gas sensor and the previous work [25]. The sensor device showed response
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(R) values of about 0.2 and 0.53 for 0.1 and 1 ppm C2H5OH, respectively.
One of empirical phenomenological formula with flat-band condition, it is known that the formulae assumes the power law form, R = Κ pgα, wherein response R = ∆R/Ro, Κ is a reaction constant, pg is a gas concentration or a partial pressure, and α is an exponent between 0 and 1 [26-27]. For our sensor, which consists of In2O3 nano-powders, may satisfy the flat-band condition, and. the data from fitting with the aforementioned equation were Κ = 0.54 and α = 0.41, which are reasonable data
that can be easily found elsewhere, as shown in Fig. 6.
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The successive alcohol gas sensing properties for our sensor was confirmed, as shown in Fig. 7, where the alcohol
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concentration was 0.2 ppm and the target gas flow on and off time duration were about 30 and 40 sec, respectively. The curve
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shape of the ratio of the sensing resistance to the base resistance (Rg/R0) for the micro gas sensor with 24 mW power
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consumption was similar to each other and the sensing curve was fully saturated with target gas and fully recovered without
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target gas.
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With low power consumption, some test results for endurance characteristics of our sensor are shown in Fig. 8, the variation of the micro-heater resistance was measured for repetitive input pulse DC power for 2104 times. Applied successive input DC
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power pulse pattern into the micro-heater with 25 mW amplitude on for 1 s and off for 1 s. The variation of the normalized micro-heater resistance RHV after 2104 times repetition operation test are shown in Fig. 8, where the variation rate of the micro-heater resistance, RHV, is below 0.3% for 2104 times repetitive 25 mW pulse operations.
4. Summary
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Low power consumption and high sensitive micro C2H5OH gas sensor was fabricated based on micro-heater using In2O3 nanopowders, which was fabricated by using CMOS compatible MEMS process. Micro gas sensor showed substantial sensitivity
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down to 0.05 ppm alcohol at lower power consumption (24 mW) with respect to that of commercial product and high
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endurance.
Acknowledgements
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This work was supported by the Ministry of Trade, Industry and Energy 'Technology development project associated with
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commercialization and by the “Sensitivity touch platform development and new industrialization support program” through the
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Biographies
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Seung Eon Moon received the BS, MS, and PhD degree in Physics from Seoul National University, Seoul, Korea in 1990, 1994 and 2000, respectively. Since 2000, he has been working for Electronics and Telecommunications Research Institute (ETRI) in the area of various application devices based on oxide materials. His current research
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activities are the development of MEMS gas sensor, piezoelectric energy harvester, ferroelectric phase shifter and
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ferroelectric or oxide non-volatile memory.
Hyung-Kun Lee is a senior researcher of Components & Materials Research Laboratory at Electronics and Telecommunications Research Institute (ETRI) in South Korea. Prior to joining ETRI, he carried out postdoctoral
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experience in Center for Smart Supramolecules, Korea in 2004 and Materials Science and Engineering at Northwestern University, USA from 2005 until 2006. He completed Ph.D. in Chemistry from the Pohang University of Science and Technology (POSTECH) in 2004, studying self-assembly of soft materials such as liquid
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crystals and supramolecular vesicles. His current research interests are mainly focused on gas sensors and their applications in actuators.
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Nak-Jin Choi received his B.S. from Pukyong National University, Korea in 1996 and M.S. and Ph.D from Kyungpook National University in 1998 and 2005, respectively. Since 2005, he has been working for Electronics
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and Telecommunications Research Institute (ETRI) in the area of various application devices based on oxide polymer.
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materials. He has been involved with research on e-nose since 1997, and also conducted research on actuators by
Hyuntae Kang received his MS degree in Chemistry from Pusan National University in 2010. He is currently pursuing a Ph.D. degree under the supervision of K.H. Park. His research interest is focused on the development of nanocatalysts for organic reaction and gas sensor. Jaewoo Lee received the B.S. degree in electrical and electronics engineering from Korea University, Seoul, Korea, in 2000, and the M.S. degree in information and communication engineering from Gwang-Ju Institute of Science and Technology (GIST), Gwangju, Korea, in 2002. After that, He joined a micro-system team at Electronics and Telecommunication Research Institute (ETRI), Daejeon, Korea. He focused on RF MEMS switches for the frontend Antenna module. Since 2006, he has developed MEMS microphones for mobile application. Seong Deok Ahn received his BS degree in Inorganic Materials Science & Engineering from Hanyang University, Seoul, Korea, in 1991, BS degree in Electronic Materials Science & Engineering from KAIST, Daejeon, Korea, in 1994, and PhD degree in Materials Science & Engineering from KAIST, Daejeon, Korea in 2000. He is
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currently a principal researcher at Components & Materials Research Laboratory in Electronics and Telecommunications Research Institute (ETRI). His current research activities are the development of touch sensors, haptic devices, flexible devices and disaplys, electronics papers and oxide TFT.
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Seong Yeol Kang received his BS degree in Physics from Seoul National University, Seoul, Korea, in 1988, BS degree and PhD in Physics from KAIST, Daejeon, Korea, in 1991 and 1994 respectively. He is currently a principal researcher at Components & Materials Research Laboratory in Electronics and Telecommunications Research
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Institute (ETRI). His current research activities are the development of touch sensors, haptic devices, flexible
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devices and disaplys, electronics papers and oxide TFT.
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20
30
40
2 (Degree)
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1k
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2k
(422)
(400)
3k
(440)
(a)
4k
0 10
10 μm
(a) XRD patterns and (b) SEM image of In2O3 nano-powders, which were deposited on Si substrate.
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Fig. 1.
(222)
5k
(b)
(211)
Intensity (A.U.)
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Fabrication processes for C2H5OH gas sensor by using CMOS compatible MEMS process
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Fig. 2.
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Enlarged image of the C2H5OH sensor (left) and the gas sensor wafer (right).
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Fig. 3.
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(a)
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(b)
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(c)
Fig. 4. The results of (a) a sensor z-axis deformation map, (b) a bridge deformation depth profile with 70.5 mW applied power
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across line aa’ and (c) a bridge z-axis deformation as a function of operating power for our sensor measured by a 3D
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vibrometer.
Fig. 5.
C2H5OH gas sensing properties of the fabricated micro gas sensor with 24 mW power consumption.
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Gas-concentration-dependent sensing properties of micro gas sensor for 0.05-1 ppm C2H5OH gas.
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Fig. 6.
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Fig. 7.
Successive gas sensing properties of the fabricated micro gas sensor with 24 mW power consumption for 0.2 ppm C2H5OH.
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Fig. 8. The temporal drift observed on the micro-heater for repetitive DC power pulse operation.
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