• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.179-179
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• 2009

This is for the electrical characterization by IDC pattern using BST$(Ba_{0.5}Sr_{0.5}TiO_3)$ thin film. BST materials had been chosen for high frequency applications due to it's high permitivity and tunability. The BST thin films have been deposited on $Al_2O_3$ Substrates by Nd-YAG pulsed laser deposition with a 355nm wavelength at $700\;^{\circ}C$. The post deposition annealing at $750^{\circ}C$ in flowing $O_2$ atmosphere for 1 hours. The capacitance of IDC patterns have been measured from 1 to 10 GHz as a function of electric field ($\pm40$ KV/cm) at room temperature using inter-digital Au electrodes deposited on top of BST. The IDC patterns have three type of fingers number. For the 10 pairs finger was the best capacitance onto $Al_2O_3$ substrate. The capacitance was 0.9pF. Also Dielectric constant was been 351 at 100 mTorr and annealing temperature $750^{\circ}C$ for 1 hour. The loss tangent was been 0.00531.

• 전자공학회논문지D
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• 제36D권4호
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• pp.63-69
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• 1999

본 연구에서는 급속 열처리 온도와 분위기를 변화 시키면서 Pt/BST/Pt 커패시터의 전기적 특성 변화를 알아보고, 특성 개선에 대한 체계적인 원인을 분석하였다. 급속 열처리의 온도와 분위기에 따른 Pt/BST/Pt 커패시터의 전기적 특성 변화는 BST 박막 내의 산소 결핍과 관련이 있는 것으로 보인다. 이러한 사실을 확인하기 위하여 450℃, 20mttorr에서 산소와 산소 플라즈마 분위기에서 각각 열처리를 수행한 후 전기적 특성을 비교하였다. 산소 플라즈마에서 열처리를 수행한 BST 커패시터의 누설전류 전류밀도가 단순히 산소 분위기에서 열처리 한 시편과 비교하여 훨씬 낮았다. 또한, 산소 분위기에서 열처리를 수행한 BST 커패시터의 유전율이 약14%정도 감소한 반면, 산소 플라즈마에서 열처리를 수행한 유전율은 거의 감소가 없었다. 위의 결과는 반응성이 강한 산소 원자를 많이 포함하고 있는 산소 플라즈마가 산소 결핍을 보상하는데 있어서 매우 효과적임을 시사하고 있다. 결과적으로, BST박막 내의 산소 결핍이 BST커패시터의 누설전류 밀도와 유전율에 큰 영향을 미치고 있음을 추정할 수 있다. 그리고, 산소 플라즈마에서 열처리를 수행함으로써 유전율의 감소 없이 누설전류 밀도가 크게 개선된 BST커패시터를 얻을 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.45-48
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• 2000

High dielectric (Ba,Sr)TiO$_3$ thin films were etched in an inductively coupled plasma (ICP) as a function of C1$_2$/Ar gas mixing ratio. Under Cl$_2$(20)/Ar(80), the maximum etch rate of the BST films was 400$\AA$/min and selectivities of BST to Pt and PR were obtained 0.4 and 0.2, respectively. We investigated the etched surface of BST by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and x-ray diffraction (XRD). From the result of XPS analysis, we found that residues of Ba-Cl and Ti-Cl bonds remained on the surface of the etched BST for high boiling point. The surface roughness decreased as Cl$_2$ increases in Cl$_2$/Ar plasma because of non-volatile etching products. This changed the nature of the crystallinity of BST. From the result of XRD analysis, the crystalliility of etched BST film maintained as similar to as-deposited BST under Ar only and Cl$_2$(20)/Ar(80). However, (100) orientation intensity of etched BST film abruptly decreased at Cl$_2$ only plasma. It was caused that Cl compounds were redeposited on the etched BST surface and damaged to crystallinity of BST film during the etch process.

• 한국전기전자재료학회논문지
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• 제17권10호
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• pp.1061-1067
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• 2004

In this study, ferroelectric (Ba,Sr)TiO$_3$ and high temperature superconductor YBCO thin films were fabricated by PLD (Pulsed Laser Deposition) method and tuneable bandstop filters were implemented with two different IDC(Interdigital Capacitance) gap patterns, 20${\mu}{\textrm}{m}$ and 30${\mu}{\textrm}{m}$ using these two thin film layers. The resonant frequency was changed by DC bias voltage. By comparing measured results with simulation, the dielectric properties of ferroelectric thin film have been extracted. The permittivity was 820 ～ 900 at 30 K and had an acceptable error range but the loss tangent had a great difference, 0.018 in 30${\mu}{\textrm}{m}$ IDC gap pattern and 0.037 in 20 ${\mu}{\textrm}{m}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.28-28
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• 2010

This study realized low-temperature crystallization process of the $Ba_{0.6}Sr_{0.4}TiO_3$ (BST) thin films without thermal damage of substrate using excimer laser annealing (ELA) and structural and electrical characteristics were investigated. The amorphous BST thin films were prepared on Pt/Ti/$SiO_2$/Si substrate by sol-gel method at $250^{\circ}C$. The ELA was carried out using KrF excimer laser which provided excitation wavelength of 248 nm. The beam homogenizing system was used in order to homogenize beam shape of Gaussian fit. The XRD and SEM were used to analyze structural characteristics and the microwave capacitance, dielectric loss and tunability of the BST films were measured by a symmetrical stripline resonator method with shorted end. Consequently, the crystallinity of BST thin films were improved after ELA process and RF tunable capacitor was demonstrated at low temperature below $300^{\circ}C$.

• Progress in Superconductivity
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• 제11권1호
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• pp.47-51
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density ($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers in $YBa_2Cu_3O_{7-{\delta}}$ films for enhancement of their $J_c$. We studied the microstructures and characteristic of $YBa_2Cu_3O_{7-{\delta}}$ films fabricated on $SrTiO_3$ (100) substrates with ZnO nanorods as pinning centers. Au catalyst nanoparticles were synthesized on STO substrates with self assembled monolayer to control the number of ZnO nanorods. The density of Au nanoparticles is approximately $240{\sim}260{\mu}m^{-2}$ with diameters of $41{\sim}49nm$. ZnO nanorods were grown on STO by hot-walled PLD with Au nanoparticles. Typical size of ZnO nanorod was around 179 nm in diameter and $2{\sim}6{\mu}m$ in length respectively. YBCO films deposited directly on STO substrates show the c-axis orientation, while YBCO films with ZnO nanorods exhibit any mixed phases without any typical crystal orientation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.719-722
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• 2004

In this work, we applied the chemical mechanical polishing (CMP) process to the planarization of ferroelectric film. We compared the structural characteristics of BST $(Ba_{0.6}Sr_{0.4}TiO_3)$ films before and after the CMP process. Their dependence on slurry composition was also investigated. Finally, we suggest the self-developed titania $(TiO_2)$ mixed abrasive slurry (MAS) for FRAM applications. Our experimental results on the ferroelectric film are encouraging for the next generation of FRAM applications.

• 한국초전도ㆍ저온공학회논문지
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• 제8권4호
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• pp.15-18
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• 2006

REBCO coated conductors (RE: rare earth elements) have recently drawn great attention since they are known to possess stronger flux pinning centers in high magnetic fields compared with YBCO coated conductors. In this study, $GdBa_2Cu_3O_{7-d}(GdBCO)$ was selected to investigate the influence of the distance between target and substrate and substrate temperature on the superconducting properties of GdBCO films on the $SrTiO_3(100)$ substrate. Samples were fabricated by pulsed laser deposition (PLD) with a Nd:YAG laser (355nm). Under a given oxygen pressure of 800mTorr, we changed the distance between target and substrate from 5.5cm to 7.0cm and the substrate temperature from $750^{\circ}C\;to\;850^{\circ}C$. The crystallinity and texture of GdBCO films were analyzed by X-ray diffraction (XRD), and the surface morphology was observed by the scanning electron microscopy (SEM). Tc and Jc values were measured by the four point probe method. High quality GdBCO films with Tc of 89.7K and Jc over $1MA/cm^2$ at 77 K in self field were successfully fabricated by optimizing processing parameters. The detailed processing conditions, microstructure and superconducting properties will be presented for a discussion.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 추계학술대회논문집
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• pp.45-48
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• 2000

High dielectric (Ba,Sr)TiO$_3$thin films were etched in an inductively coupled plasma (ICP) as a function of C1$_2$/Ar gas mixing ratio. Under Cl$_2$(20)/Ar(80), the maximum etch rate of the BST films was 400$\AA$/min and selectivities of BST to Pt and PR were obtained 0.4 and 0.2, respectively. We investigated the etched surface of BST by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and x-ray diffraction (XRD). From the result of XPS analysis, we found that residues of Ba-Cl and Ti-Cl bonds remained on the surface of the etched BST for high boiling point. The surface roughness decreased as Cl$_2$increases in C1$_2$/Ar plasma because of non-volatile etching products. This changed the nature of the crystallinity of BST. From the result of XRD analysis, the crystallinity of etched BST film maintained as similar to as-deposited BST under Ar only and Cl$_2$(20)/Ar(80). However, (100) orientation intensity of etched BST film abruptly decreased at Cl$_2$only plasma. It was caused that Cl compounds were redeposited on the etched BST surface and damaged to crystallinity of BST film during the etch process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.200-200
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• 2008

This paper reports on electrical characterization by IDC pattern using BST$(Ba_{0.5}Sr_{0.5}TiO_3)$ thin film. BST thin films have been deposited on $Al_2O_3$ Substrates by Nd-YAG pulsed laser deposition with a 355nm wavelength at $700^{\circ}C$. The post deposition annealing at $750^{\circ}C$ in flowing $O_2$ atmosphere for I hours. The capacitance of IDC patterns have been measured from 1 to 10 GHz as a function fo electric field (${\pm}40$ KV/cm) at room temperature using interdiigitated Au electrodes deposited on top of BST. The IDC patterns have three type of fingers number. For the finger paris was increased onto $Al_2O_3$, the capacitance increased. The capacitance of 5 pairs finger was 0.3pF and 10 pairs finger was 0.9pF.