• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.247-248
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• 2006

Carbon nitride films were evaluated that they had many advantages for miniature micro-humidity-sensors using the standard CMOS technology humidity sensing properties and CV characteristics of the carbon nitride films have been investigated for fabricating one chip HUSFET(Humidity Sensitive Field Effect Transistor) humidity sensors Carbon nitride films were deposited on silicon substrate with meshed electrodes by reactive RF magnetron sputtering system. The capacitor-type humidity sensor revealed good humidity-impedance characteristics with a wide range of relative humidity changes, decreasing $254k{\Omega}$ to $16k{\Omega}$ according to increase of relative humidity between 5% ~ 95% and the films were very stable on the Si wafer. These results reveal that $CN_x$ thin films can be used for Si based or HUSFET structure one chip micro-humidity sensors.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.507-513
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• 1999

8mol%-yttria-stabilized zirconia(YSZ) thin films as oxygen ion conductor were deposited by rf-magnetron sputtering, and the oxygen gas sensors with the structure of $SiO_2$ substrate/Ni-NiO mixed reference layer/Pt/YSZ/Pt were fabricated and their oxygen sensing properties were investigated. The steady-state electro-motive force (EMF) values were measured as a function of oxygen partial pressure ($PO_2;form 1.013\times10^3 \textrm{Pa \;to}\; 1.013\times10^5$Pa) and operating temperature ($300^{\circ}C$ to $700^{\circ}C$). The fabricated YSZ oxygen sensor showed the best oxygen sensing properties at 50$0^{\circ}C$. However, oxygen sensing properties were very low at the temperature lower than 30$0^{\circ}C$ due to the lack of oxygen ion mobility and at the temperature higher than $700^{\circ}C$ due 새 intermixing of materials between the layers. Especially, the YSZ sensor operating at $500^{\circ}C$ and oxygen partial pressure above $1.565\times10^4$Pa showed the oxygen sensing properties close to the values predicted by ideal Nernst equation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1296-1300
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• 2004

SnO$_2$ is one of the most suitable gas sensor materials. The microstructure and surface morphology of films must be controlled because the electrical and optical properties of SnO$_2$ films depend on these characteristics. The effects of chemical mechanical polishing(CMP) on the variation of morphology of SnO$_2$ films prepared by RF sputtering system were investigated. The commercially developed ceria-based oxide slurry, silica-based oxide slurry, and alumina-based tungsten slurry were used as CMP slurry. Non-uniformities of all slurries met stability standards of less than 5 %. Silica slurry had the highest removal rate among three different slurries, sufficient thin film topographies and suitable root mean square(RMS) values.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.888-891
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• 2003

This paper describes on the fabrication and characteristics of micro ceramic thin-film type pressure sensors based on Ta-N strain-gauges for high-temperature applications. The Ta-N thin-film strain-gauges are deposited onto thermally oxidized Si diaphragms by RF sputtering in an argon-nitrogen atmosphere($N_2$ gas ratio: 8 %, annealing condition: $900^{\circ}C$, 1 hr.), Patterned on a wheatstone bridge configuration, and use as pressure sensing elements with a high stability and a high gauge factor. The sensitivity is $1.097{\sim}1.21mV/V.kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS. The fabricated pressure sensor presents a lower TCR, non-linearity than existing Si piezoresistive pressure sensors. The fabricated micro ceramic thin-film type pressure sensor is expected to be usefully applied as pressure and load sensors that is operable under high-temperature environments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.13-13
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• 2010

Piezoelectric sensors are extensively used to measure force because of their high sensitivity and low cost. however, the development of device with reduced size but with improved sensitivity is highly important. Low-temperature co-fired ceramic (LTCC) is one of promising materials for this application than a silicon substrate because it has very good electrical and mechanical properties as well as possibility of making various three dimensional (3D) structures. In this work, piezoelectric pressure sensors based on hybrid LTCC technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The piezoelectric sensing layer consists of PZT thin film deposited by RF magnetron sputtering method on between top and bottom Au electrodes. The PZT films deposited on LTCC diaphragms were successfully grown and were analyzed by using X-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM).

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.7
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• pp.711-717
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• 2007

Location information will become increasingly important for future Pervasive Computing applications. Location tracking system of a moving device can be classified into two types of architectures: an active mobile architecture and a passive mobile architecture. In the former, a mobile device actively transmits signals for estimating distances to listeners. In the latter, a mobile device listens signals from beacons passively. Although the passive architecture such as Cricket location system is inexpensive, easy to set up, and safe, it is less precise than the active one. In this paper, we present a passive location system using Cricket Mote sensors which use RF and ultrasonic signals to estimate distances. In order to improve accuracy of the passive system, the transmission speed of ultrasound was compensated according to air temperature at the moment. Upper and lower bounds of a distance estimation were set up through measuring minimum and maximum distances that ultrasonic signal can reach to. Distance estimations beyond the upper and the lower bounds were filtered off as errors in our scheme. With collecting distance estimation data at various locations and comparing each distance estimation with real distance respectively, we proposed an equation to compensate the deviation at each point. Equations for proposed algorithm were derived to calculate relative coordinates of a moving device. At indoor and outdoor tests, average location error and average location tracking period were 3.5 cm and 0.5 second, respectively, which outperformed Cricket location system of MIT.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.46-53
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• 1997

The TMA gas sensors are fabricated with the ZnO-based thin films grown by a RF magnetron sputtering method. The hall effect measurement and AES analysis are carried out to investigate the effects of the sputtering gases and dopants which effect on the electrical resistivity and sensitivity to TMA gas. We measure the cfhanges of the surface carrier concentration, haall electron mobility, electrical resistivity, surface condition, and depth profile of the films. The ZnO-based thin film sensors sputtered in oxygen, or added with dopants showed a high sruface carrier concentration, film sensors sputtered in oxygen and doped with 4.0 wt.% $Al_{2}$O$_{3}$, 1.0 wt.% TiO$_{2}$, and 0.2 wt% v$_{2}$O$_{5}$ showed the highest surface carrier concentration of 5.952 * 10$^{20}$ cm$^{-3}$ , hall electron mobility of 176.7 cm$^{2}$/V.s, lowest electrical resistivity of 6*10$^{-5}$ .ohm.cm and highest sensitivity of 12. These results were measured at a working temperature of 300.deg. C to 8 ppm TMA gas.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3_1spc
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• pp.607-614
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• 2013

This paper proposes a robot driving system and sensor implementation for use with an education robot. This robot has multiple functions and was designed so that children could use it with interest and ease. The robot recognizes the location of a user and follows that user at a specific distance when the robot and user communicate with each other. In this work, the robot was designed and manufactured to evaluate its performance. In addition, an embedded board was installed with the purpose of communicating with a smart phone, and a camera mounted on the robot allowed it to monitor the environment. To allow the robot to follow a moving user, a set of sensors combined with an RF module and ultrasonic sensors were adopted to measure the distance between the user and the robot. With the help of this ultrasonic sensors arrangement, the location of the user couldbe identified in all directions, which allowed the robot to follow the moving user at the desired distance. Experiments were carried out to see how well the user's location could be recognized and to investigate how accurately the robot trackedthe user, which eventually yielded a satisfactory performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.152-155
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• 2006

Carbon nitride ($CN_X$) films were prepared by reactive RF magnetron sputtering system at various deposition conditions and the C-V characteristics of MIS(metal - insulator - semiconductor) capacitors that have the structures of Al/$CN_x$/p-Si/Al and Al/$CN_x$/$Si_3N_4$/p-Si/Al were investigated. The resistivity of carbon nitride was above $2.40{\times}10^8{\Omega}{\cdot}cm$ at room temperature. The C-V plot showed a typical capacitance-voltage characteristics of semiconductor insulating layers, while it showed hysterisis due to interface charges. Amorphous carbon nitride (a-$CN_x$) films, that have relatively high resistivity and low dielectric constant could be useful as interlayer insulator materials of VLSI(very large-scale integration) and ULSI(ultra large-scale integration).

• Journal of Surface Science and Engineering
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• v.40 no.6
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• pp.258-261
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• 2007

Relationships between the electrical resistivity and the growth characteristic of $SnO_2$ thin films were investigated. $SnO_2$ thin films with thickness from 64 nm to 91 nm were made by controlling the RF deposition energy from 80 to 150 W. These $SnO_2$ thin films were annealed at $200^{\circ}C{\sim}700^{\circ}C$ temperature range of $100^{\circ}C$ interval in the $O_2$ gas condition. After annealing treatments, the microstructures of the $SnO_2$ thin films were changed mixed structure(amorphous & crystalline) to lamina columnar crystalline structure. Both the film thickness and the grain size were increased with increasing the local crystallization of $SnO_2$ microstructure of thin films by annealing treatment. Their electrical resistivity increased up to the annealing temperature of $400^{\circ}C$, and then slowly decreased.