• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.560-565
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• 2008

$(Pb_{0.98}La_{0.08})(Zr_{0.65}Ti_{0.35})O_3$ (PLZT) thin films with $TiO_2$ buffer layers were deposited on Pt/Ti/$SiO_2$/Si substrates by an R.F. magnetron sputtering method in order to improve the ferroelectric characteristics of the films. And the ferroelectric properties and crystallinities of the PLZT thin films were investigated in terms of the effects of the post annealing temperatures of $TiO_2$ buffer layers between a platinum bottom electrode and PLZT thin film. The ferroelectric properties of the PLZT thin films improved as increasing of the post annealing temperatures of $TiO_2$ layers, thereby reaching their maximum at $600^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.51-59
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• 1996

A flow sensor has been fabricated by preparing thin film Pt-heater and Bi-Sb thermocouples array on 150 nm-$Si_{3}N_{4}$/300 nm-$SiO_{2}$/150 nm-$Si_{3}N_{4}$ dielectric diaphragm which has low thermal conductivity and balanced stress with silicon substrate for the purpose of improving the thermal isolation between heater and silicon substrate. Pt-heater showed nonlinear I-V characteristics due to the thermal isolation effect of the diaphragm. Its temperature coefficient of resistance was about $0.00378\;/^{\circ}C$ and Seebeck coefficient of Bi-Sb thermocouple was about $97\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and flow sensitivity increased as heater voltage increased or as the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_{2}$-flow sensitivity and thermal response time of the sensor were about $1.27\;mV{\cdot}(sccm)^{-1/2}$ and 0.13 sec., respectively.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.56-62
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• 1997

Using a rf-magnetron sputtering method, highly c-axis oriented La modified $PbTiO_{3}$ (PLT) ferroelectric thin films with compositions of $(Pb_{1-x}La_{x})Ti_{1-x/4}O_{3}$, where x=0.05, x=0 and x=0.15, have been obtained on (100)MgO single crystal substrate under conditions of low gas pressure. The degree of c-axis orientation of PLT films decreases with increasing gas pressure and with increasing La contant. These films were characterized by X-ray diffraction and SEM. PLT thin films of x=0.05, 0.1 and 0.15 show a low dielectric constant of 218, 246 and 361 at 1 kHz and remanent polarization(Pr) of $9{\mu}C/cm^{2}$, $8{\mu}C/cm^{2}$ and $7{\mu}C/cm^{2}$.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.6-15
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• 1997

This paper presents the multi-objective optimal design of thermopile sensor having beam or membrane structure. The thermopile sensor is composed of $Si_{3}N_{4}/SiO_{2}$ dielectric membrane, Al-polysilicon thermocouples and $RuO_{2}$ thin film for black body. The sensing method is based on the Seebeck effect which is originated from the temperature difference of the two positions, black body and silicon rim. The objective functions of the presented design are sensitivity, detectivity and thermal time constant. The modelling of the sensor is proposed including the package. The multi-objective optimization technique is applied to the design of the sensor not only inspecting the modelling equation but also simulating mathematical programming method. Especially, fuzzy optimization technique is adapted to get the optimal solution which enables the designer to reach the more practical solution. The design constraint of the voltage output originated from the change of the environmental temperature is included for practical use.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.285-292
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• 1992

Ultrathin(8nm) oxynitride (SiOxNy) film have been formed on Si(100) by rapid thermal processing(RTP) in $O_2$and $N_2$O as reactants. Compared with conventional furnace $O_2$ oxide, the oxynitride dielectrics shows better characteristics of I-V and TDDB, and less flat-band voltage shift. The oxynitride has a behavior of Fowler-Nordheim tunneling in the region of V 〉${\varphi}_0$ simialr to pure Si$O_2$oxide. The relative dielectric constant of oxynitride is higher than that of conventional pure oxide. Excellent diffusion harrier property to dopant(B$F_2$) is also observed. Nitrogen depth profiles by SIMS, AES, and XPS show nitrogen pile - up at Si$O_2$/Si interface, which can explain the improved properties of oxynitride dielectrics.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.158-165
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• 2010

This study reviewed terahertz technologies of time domain spectroscopy, T-ray imaging, and high rate wireless data transfer. The main topics of the terahertz research area were investigation of materials and package modules for terahertz wave generation and detection, and setup of the terahertz system for time domain spectroscopy(TDS), T-ray imaging and sub-THz wireless communication. In addition to Poly-GaAs film as a photoconductive switching antenna material, a table-top scale for the THz-TDS/imaging system and terahertz continuous wave(CW) generation systems for sub-THz data transfer and narrow band T-ray imaging were designed. Dielectric properties of ferroelectric BSTO($Ba_xSr_{1-x}TiO_3$) films and chalcogenide glass systems were characterized with the THz-TDS system at the THz frequency range. Package modules for terahertz wave transmitter/receiver(Tx/Rx) photoconductive antenna were developed.

• Korean Journal of Materials Research
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• v.4 no.4
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• pp.401-405
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• 1994

The chemical composition and electrical properties were investigated for epitaxially crystallized $(Ba_{0.5}Sr_{0.5})Tio_3$ (BST) films deposited on Pt and $YBa_Cu_3O_{7-x}$(YBCO) electrodes by laser ablation technique. The crystalline quality of the heteroepitaxial BST films deposited on Pt bottom electrode was found to be better than that of BST film on YBCO electrode by the RBS analysis. Films deposited at $600^{\circ}C$ on Pt electrode showed a dielectric constant of 320 and a dissipation factor of 0.023 at 100kHz. Leakage current density of BST films on Pt electrode was smaller than that on YBCO bottom electrode. Their leakage current density was about 0.8$\mu \; A/ \textrm{cm}^2$ at an applied electric field of 0.15MV/cm.

• Korean Journal of Materials Research
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• v.4 no.4
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• pp.453-458
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• 1994

$(Ba_{0.5}Sr_{0.5)/TiO_3$(BST) thin films were prepared for the application of 256 Mb DRAM by RF magnetron sputtering. The crystallinity of BST thin films increased with increasing deposition tempera lure. The composition of thin films was $(Ba_{0.48}Sr_{0.48)/TiO_{2.93}$ Pt/Ti barrier layer suppressed the diffusion of Si into BST layer. The films showed a dielectric constant of 320 and a dissipation factor of 0.022 at 100 kHz. the change of capacitance of the films with applied voltage was small, showing paraelectric property. The charge storage density and leakage current density were 40fC/$\mu \textrm{m}^{2}$ and 0.8$\mu A/\textrm{cm}^2$, respectively at a field of 0.15 MV/cm. The BST films obtained by RF magnetron sputtering appeared to be potential thin film capacitors for 256 Mb DRAM application.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.454-458
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• 2012

Various adhesive materials are used in flip chip packaging for electrical interconnection and structural reinforcement. In cases of COF(chip on film) packages, low temperature bonding adhesive is currently needed for the utilization of low thermal resistance substrate films, such as PEN(polyethylene naphthalate) and PET(polyethylene terephthalate). In this study, the effects of anhydride and dihydrazide hardeners on the low-temperature snap cure behavior of epoxy based non-conductive pastes(NCPs) were investigated to reduce flip chip bonding temperature. Dynamic DSC(differential scanning calorimetry) and isothermal DEA(dielectric analysis) results showed that the curing rate of MHHPA(hexahydro-4-methylphthalic anhydride) at $160^{\circ}C$ was faster than that of ADH(adipic dihydrazide) when considering the onset and peak curing temperatures. In a die shear test performed after flip chip bonding, however, ADH-containing formulations indicated faster trends in reaching saturated bond strength values due to the post curing effect. More enhanced HAST(highly accelerated stress test) reliability could be achieved in an assembly having a higher initial bond strength and, thus, MHHPA is considered to be a more effective hardener than ADH for low temperature snap cure NCPs.

• Journal of the Korean Vacuum Society
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• v.12 no.1
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• pp.40-45
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• 2003

High quality $Ta_2O_5$ thin films have been obtained from the anodization of deposited tantalum (Ta). The as-deposited amorphous films of 750 $\AA$ thickness have excellent electrical properties. These properties include refractive indices 2.1~2.2 dielectric constants ~25, and leakage currents $10^{-8}$ /A$\textrm{cm}^{-2}$ at 1 MV$\textrm{cm}^{-1}$. We fabricated a MIM element with the $Ta_2O_5$ films. They have perfect current-voltage symmetry characteristics. A high performance MIM device was formed by newly developed processes based on our unique anodization and annealing treatment. The effects of various processing conditions (top-electrode metals, annealing conditions) on the MIM device performances will be extensively discussed throughout this work.