• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.918-920
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• 1999

Recently, the ceramics of high permittivity are applied to DRAM and FRAM. In this study, (Ba, Sr)$TiO_3$ (BST) ceramics thin films were prepared by Sol-Gel method. BST solution was made and spin-coated on Pt/$SiO_2$/Si substrate at 4000[rpm] for 10 seconds. Coating process was repeated 3 times and then sintered at $750[^{\circ}C]$ for 30 minutes. Each specimen was analyzed structure and electrical characteristics. Thickness of BST ceramics thin films are about $2000[\AA]$. Dielectric constant and loss of thin films was little decreased at $1[kHz]{\sim}1[MHz]$. Dielectric constant and loss to frequency were 250 and 0.02 in BST3. In accordance with applied voltage, property of leakage current was stability when the was $0{\sim}3$[V]. According to voltage, leakage current was increased exponentially at $4{\sim}7$[V].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.29-32
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• 2004

This work was devoted to an investigation of etching mechanisms for $(Ba,Sr)TiO_3$ (BST) thin films in inductively coupled $CF_4/Ar$ plasma. We have found that an increase of the Ar content in $CF_4/Ar$ plasma causes non-monotonic behavior of BST etch rate, which reaches a maximum value of 40 nm/min at 80% Ar. Langmuir probe measurements show a weak sensitivity of both electron temperature and electron density to the change of $CF_5/Ar$ mixing ratio. O-D model for plasma chemistry gave monotonic changes of both volume densities and fluxes for active species responsible for the etching process. The analysis of surface kinetics confirms the possibility of non-monotonic etch rate behavior due to the concurrence of physical and chemical pathways in ion-assisted chemical reaction.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.33-39
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• 1998

The BST (Ba$_{1-x}$ Sr$_{x}$TiO$_{3}$)(50/50) thin film has been grown by RF magnetron reactive sputtering and its characteristics such as crystallization, surface roughness, and electrical properties have been investigated with varying the film thickness. The crystallization and surface roughness of BST thin film are investigated by using XRD and AFM, respectively The BST thin film anealed at 800.deg. C for 2 min has pure perovskite structure and good surface roughness of 16.1.angs.. We estimate that the thickness and dielectric constant of interface layer between BST film and electrode are 3nm and 18.9, respectively, by measuring the capacitance with various film thickness. As the film thickness increases form 80nm to 240nm, the dielectric constant at 10kHz increases from 199 to 265 and the leakage current density at 200kV/cm decreases from 0.682.mu.A/cm$^{2}$ to 0.181 .mu.A/cm$^{2}$. In the case of 240nm-thick BST thin film, the charge storage density and leakage current density at 5V are 50.5fC/.mu.m$^{2}$ and 0.182.mu.A/cm$^{2}$, respectively. The values indicate that the BST thin film is a very useful dielectric material for the DRAM capacitor.or.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.869-873
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• 2004

[ $Sr_xBa_{1-x}Nb_2O_6$ ] (SBN, $0.25{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient, piezoelectric, and a photo refractive properties. In this study, SBN60(x=0.6) thin film was manufactured by ion beam sputtering technique. Using the prepared SBN60 target in $Ar/O_2$ atmosphere as-deposited SBN60 thin film on Pt(100)/$TiO_2/SiO_2/Si$ substrate crystallization and orientation behavior as well as electric properties of SBN60 thin film were examined. SBN60 deposition up to $3000{\AA}$ in thickness, SBN60 thin film was heat-treated at $650^{\circ}C{\sim}800^{\circ}C$. The orientation was shown primarily along (001) plane from XRD pattern where working pressure was $4.3{\times}10^{-4}$ torr. The deposited layer was uniform, preferred orientatin and crystallization behavior resulted in the change of $O_2$ ratio was observed. In electric propertie of Pt/SBN60/Pt thin film capacitor remnant polarization (2Pr) value was $10{\mu}C/cm^2$, the coercive filed (Ec) 50 kV/cm, and the dielectric constant 615, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.79-79
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• 2008

We report the growth of $Ba_{0.5}Sr_{0.5}TiO_3$(BST) thin films and their substrate-dependent electrical characteristics. BST thin films were deposited on alumina(non-single crystal), $Al_2O_3$(100) substrates by Nd:YAG Pulsed Laser Deposition(PLD) with a 355nm wavelength at substrate temperature of $700^{\circ}C$ and post-deposition annealing at $750^{\circ}C$ in flowing $O_2$ atmosphere for 1hours. BST materials had been chosen due to high dielectric permittivity and tunability for high frequency applications, To analyze the oxygen partial pressure effects, deposited films at 1, 10, 50, 100, 150, 200, 300 mTorr. The effects of oxygen pressure on structural properties of the deposited films have been investigated by X-ray diffraction(XRD) and atomic force microscope(AFM), respectively. Then we manufactured a inter-digital capacitor(IDC) patterns twenty fingers and $10{\mu}m$ gap, $700{\mu}m$ length and electrical properties were characterized. The results provide a basis for understanding the growth mechanisms and basic structural and electrical properties of BST thin films as required for tunable microwave devices applications such as varactors and tunable filters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.249-249
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• 2009

We have grown large area BSTO($(Ba_{1-x}Sr_x)TiO_3$) thin films (x=0.4) on 2 inch diameter MgO (001) single crystal substrates using a pulse laser deposition(PLD) system. Substrate temperature and oxygen pressure in the deposition chamber, and the laser optics for ablating a target have been controlled to obtain the uniform thickness and preferred orientation of the films. Results of x-ray diffraction and rocking curve analysis revealed that the BSTO films were grown on MgO substrates with a preferred orientation (002), and the full width half maximum of the rocking curve was measured to be 0.86 degree at optimum condition. Roughness of the films have been measured to be $3.42{\AA}$ rms by using atomic force microscopy. We have successfully deposited the large area BSTO thin films of $4000{\AA}$ thickness on 50 mm diameter MgO substrates.