• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1988-1990
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• 1996

In this work, we have grown or evaporated thermal oxide and E-beam oxide on the (100) oriented n-type silicon wafers, respectively and they were directly bonded with another silicon wafer after hydrophilization using solutions of three types of $HNO_3$, $H_{2}SO_{4}$ and $NH_{4}OH$. Changes of average surface roughness after hydrophilizations of the single crystalline silicon wafer, thermal oxide and E-beam evaporated silicon oxide were studied using atomic force microscope. Bonding interfaces of the bonded pairs were inspected using scanning electron microscope. Void and non-contact area of the bonded pairs were also inspected using infrared transmission microscope.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.556-561
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• 2001

We prepared a new a SOS(silicon-on-silicide) wafer pair which is consisted of Si(100)/1000$\AA$-NiSi Si (100) layers. SOS can be employed in MEMS(micro- electronic-mechanical system) application due to low resistance of the NiSi layer. A thermally evaporated $1000\AA$-thick Ni/Si wafer and a clean Si wafer were pre-mated in the class 100 clean room, then annealed at $300~900^{\circ}C$ for 15hrs to induce silicidation reaction. SOS wafer pairs were investigated by a IR camera to measure bonded area and probed by a SEM(scanning electron microscope) and TEM(transmission electron microscope) to observe cross-sectional view of Si/NiSi. IR camera observation showed that the annealed SOS wafer pairs have over 52% bonded area in all temperature region except silicidation phase transition temperature. By probing cross-sectional view with SEM of magnification of 30,000, we found that $1000\AA$-thick uniform NiSi layer was formed at the center area of bonded wafers without void defects. However we observed debonded area at the edge area of wafers. Through TEM observation, we found that $10-20\AA$ thick amourphous layer formed between Si surface and NiSix near the counter part of SOS. This layer may be an oxide layer and lead to degradation of bonding. At the edge area of wafers, that amorphous layer was formed even to thickness of $1500\AA$ during annealing. Therefore, to increase bonding area of Si NiSi ∥ Si wafer pairs, we may lessen the amorphous layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.147-150
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• 2003

In this paper, We fabricated a high temperature pressure sensor using SBD(silicon- direct-bonding) wafer of $Si/SiO_2$/Si-sub structure. This sensor was very sensitive because the piezoresistor is fabricated by single crystal silicon of the first layer of SDB wafer. Also, it was possible to operate the sensor at high temperature over $120^{\circ}C$ which is the temperature limitation of general silicon sensor because the piezoresistor was dielectric isolation from silicon substrate using silicon dioxide of the second layer. The sensitivity of this sensor is very high as the measured result of D2200 shows $183.6\;{\mu}V/V{\cdot}kPa$. Also, the output characteristic of linearity was very good. This sensor was available at high temperature as $300^{\circ}C$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.588-592
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• 2004

This paper presents the preliminary fabrication results of colloid thrusters which can provide thrust of the order of micro to milli-Newtons. MEMS technology has been used for fabrication, and four essential fabrication techniques - deep etching with nested masks, isotropic plasma etching, anisotropic reactive ion etching, and direct fusion wafer bonding - have been newly developed. Among diverse models which have been designed and fabricated, the fabrication results of 4-inch wafer-based colloid thrusters are presented.

• The Korean Journal of Ceramics
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• v.7 no.1
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• pp.36-40
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• 2001

In order to fabricate uncooled IR sensors for pyroelectric applications, multilayered thin films of Pt/PbTiO$_3$/Pt/Ti/Si$_3$N$_4$/SiO$_2$/Si and thermally isolating membrane structures of square-shaped/cantilevers-shaped microstructures were prepared. Cavity was also fabricated via direct silicon wafer bonding and etching technique. Metallic Pt layer was deposited by ion beam sputtering while PbTiO$_3$ thin films were prepared by sol-gel technique. Micromachining technology was used to fabricate microstructured-membrane detectors. In order to avoid a difficulty of etching active layers, silicon-nitride membrane structure was fabricated through the direct bonding and etching of the silicon wafer. Although multilayered thin film deposition and device fabrications were processed independently, these could b integrated to make IR micro-sensor devices.

• Journal of Biomedical Engineering Research
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• v.37 no.5
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.2
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• pp.95-100
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• 2006

The GaAs-on-insulator (GOI) wafer fabrication technique has been developed by using ion-cut process, based on hydrogen ion implantation and wafer direct bonding techniques. The hydrogen ion implantation condition for the ion-cut process in GaAs and the associated implantation mechanism have been investigated in this paper. Depth distribution of hydrogen atoms and the corresponding lattice disorder in (100) GaAs wafers produced by 40 keV hydrogen ion implantation were studied by SIMS and RBS/channeling analysis, respectively. In addition, the formation of platelets in the as-implanted GaAs and their microscopic evolution with annealing in the damaged layer was also studied by cross-sectional TEM analysis. The influence of the ion fluence, the implantation temperature and subsequent annealing on blistering and/or flaking was studied, and the optimum conditions for achieving blistering/splitting only after post-implantation annealing were determined. It was found that the new optimum implant temperature window for the GaAs ion-cut lie in $120{\sim}160^{\circ}C$, which is markedly lower than the previously reported window probably due to the inaccuracy in temperature measurement in most of the other implanters.

• Advances in nano research
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• v.2 no.1
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• pp.1-14
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• 2014

Dislocations are basic crystal defects and represent one-dimensional native nanostructures embedded in a perfect crystalline matrix. Their structure is predefined by crystal symmetry. Two-dimensional, self-organized arrays of such nanostructures are realized reproducibly using specific preparation conditions (semiconductor wafer direct bonding). This technique allows separating dislocations up to a few hundred nanometers which enables electrical measurements of only a few, or, in the ideal case, of an individual dislocation. Electrical properties of dislocations in silicon were measured using MOSFETs as test structures. It is shown that an increase of the drain current results for nMOSFETs which is caused by a high concentration of electrons on dislocations in p-type material. The number of electrons on a dislocation is estimated from device simulations. This leads to the conclusion that metallic-like conduction exists along dislocations in this material caused by a one-dimensional carrier confinement. On the other hand, measurements of pMOSFETs prepared in n-type silicon proved the dominant transport of holes along dislocations. The experimentally measured increase of the drain current, however, is here not only caused by an higher hole concentration on these defects but also by an increasing hole mobility along dislocations. All the data proved for the first time the ambipolar behavior of dislocations in silicon. Dislocations in p-type Si form efficient one-dimensional channels for electrons, while dislocations in n-type material cause one-dimensional channels for holes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.958-962
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• 2002

This paper reports on the fabrication of free-standing microstructures by DRIE (deep reactive ion etching). SOI (Si-on-insulator) structures with buried cavities are fabricated by SDB (Si-wafer direct bonding) technology and electrochemical etch-stop. The cavity was formed the upper handling wafer by Si anisotropic etch technique. SDB process was performed to seal the formed cavity under vacuum condition at -760 mmHg. In the SDB process, captured air and moisture inside of the cavities were removed by making channels towards outside. After annealing (100$0^{\circ}C$, 60 min.), the SDB SOI structure with a accurate thickness and a good roughness was thinned by electrochemical etch-stop in TMAH solution. Finally, it was fabricated free-standing microstructures by DRIE. This result indicates that the fabrication technology of free-standing microstructures by combination SDB, electrochemical etch-stop and DRIE provides a powerful and versatile alternative process for high-performance bulk micromachining in MEMS fields.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.682-691
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• 2005

This paper describes the design, fabrication, and testing of a microturbine developed at Seoul National University. Here, the term 'microturbine' refers to a radial turbine with a diameter on the order of a centimeter. Such devices can be used to transmit power for various systems. The turbine is designed using a commercial CFD code, and it has a design flow coefficient of 0.238 and work coefficient of 0.542. It has 31 stator blades and 24 rotor blades. A hydrodynamic journal bearing and hydrostatic thrust bearings counteract radial and axial forces on the rotor. The test turbine consists of a stack of five wafers and is fabricated by MEMS technology, using photolithography, DRIE, and bonding processes. The first, second, fourth, and fifth layers contain plumbing, and hydrostatic axial thrust bearings for the turbine. The third wafer contains the turbine's stator, rotor, and hydrodynamic journal bearings. Furthermore, a turbine test facility containing a flow control system and instrumentation has been designed and constructed. In performance tests, a maximum rotation speed of 11,400 rpm and flow rate of 16,000 sccm have been achieved.