• 한국세라믹학회지
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• 제33권11호
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• pp.1195-1202
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• 1996

To prepare the dielectric thin films of (Pb1-xSrx)TiO3 (x=0.1, 0.2, 0.3, 0.35, 0.5) by the sol-gel process titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) and Pb Sr, acetate were used therefore the thin films were fabricated by dip-coating method. Stability of the sol decreased with addition of Sr content thin films could be fabricated up to 35mol% Over this range precipitation of sol occured thin films couldn't be obtained. Transmittance of thin films at visible range decreased with the increase of heat-treatment temperature but exhibited transmit-tance above 60% in all case. Moreover transmittance of thin films at visible range slightly increased with of addition of Sr,. When thin film containing 30 mol% srontium was heated at 600℃ the best perovskite phase was obtained. The dielectric constant (ε) was 280 and dielectric loss factor (tan δ) was 0.021 and curie tempera-ture (Tc) decreased with the increase of addition of Sr.

• 한국진공학회지
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• 제4권S1호
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• pp.138-144
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• 1995

It is commonly believed that high permittivity materials will be necessary for future high density Gbit DRAMs. In a first part, we explain the choice of SrTiO3 by ECR MOCVD for Gbit-scale DRAMs. In a second part, after describing the ECR MOCVD system and presenting the requirements SrTiO3 thin films should meet for use in Gbit-scale DRAMs, the physical and electrical properties of srTiO3 thi film prepared by ECR MOCVD are then studied. A stacked capacitor technology, suitable for use in 1 Gbit DRAM, and comprising high permittivity SrTiO3 thin films prepared by ECR MOCVD at $450^{\circ}C$ on electron beam and RIE patterned RuO2/TiN storage nodes is finally described.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.649-652
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• 1999

The (Ba, Sr)TiO$_3$(BST) thin films were fabricated on Pt/Ti/SiO$_2$/Si substrate by RF sputtering technique. The structural properties of the BST thin films were investigated with substrate temperature by XRD, SEM, EDS and AES depth profils. Increasing the substrate temperature, barium multi titanate phases were decreased. The BST thin film had a structure of perovskite type, and had peaks of (100), (200) at the substrate temperature of 50$0^{\circ}C$. When the BST thin films were deposited at the substrate temperature of 50$0^{\circ}C$, the composition ratio of Ba/sr was 52/48.

• 한국재료학회지
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• 제10권9호
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• pp.607-611
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• 2000

고밀도 DRAM에서 박막 커패시터로의 적용을 위해 Zr이 첨가된 (Ba(sub)1-x, Sr(sub)x)TiO$_3$<원문차조> 박막이 r.f. magnetron sputter-ing 법에 의해 제조되었다. 증착된 박막들은 다결정질 구조를 보였으며 증착압력이 감소함에따라 Zr/Ti의 비가 현저히 증가하였으며 본 연구에서는 얻어진 박막들은 100kHz에서 380∼525의 유전상수값을 나타냈다. 전압에 따른 커패시턴스와 분극량의 변화는 이력특성을 크게 보이지 않아 상유전상으로 형성되었음을 보였다. 누설전류밀도는 증착압력이 감소함에 따라 작아지는 경향을 보였고 10mTorr이상에서 증착된 박막의 경우 200kV/cm의 전계에서 10(sup)-7∼10(sup)-8A/$\textrm{cm}^2$의 차수를 갖는 누설전류밀도를 보여 본 연구에서 제조된 (Ba(sub)1-x, Sr(sub)x)(Ti(sub)1-x, Zr(sub)x)O$_3$<원문참조>박막은 고밀도 DRAm을 위한 커패시터에의 적용가능성을 보였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권5호
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• pp.265-269
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• 2000

$(Ba, Sr)TiO_3$thin films were etched with a magnetically enhanced inductively coupled plasma (MEICP) at different CF4/Ar gas mixing ratios. Experimental was done by varying the etching parameters such as rf power, dc bias and chamber pressure. The maximum etch rate of the BST films was $1800{AA}/min$ under $CF_4/(CF_4+Ar)$ of 0.1, 600 W/350 V and 5 mTorr. The selectivity of BST to Pt and PR was 0.6, 0.7, respectively. X-ray photoelectron spectroscopy (XPS) results show that surface reaction between Ba, Sr, Ti and C, F radicals occurs during the (Ba, Sr)TiO3 etching. To analyze the composition of surface residue after the etching, films etched with different CF_4/Ar$ gas mixing ratio were investigated using XPS and secondary ion mass spectroscopy (SIMS).

• 한국세라믹학회지
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• 제36권10호
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• pp.1075-1079
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• 1999

LaSrCoO3 thin films were spin-coated onto the SrTiO3(100) substrates by the chemical solution process. X-ray diffraction $\theta$-2$\theta$ scans and X-ray diffraction $\beta$ scans were used to determine the crystallinity and in -plane alignment behavior of the films. The X-ray diffraction pattern showed the film obtained by annealing at 80$0^{\circ}C$ was highly oriented. The X-ray diffraction pole-figure analysis and reciprocal-space mapping (2$\theta$-$\Delta$$\omega$ scans) of the resulting film showed that the film comprising the pseduocubic phase had an epitaxial relationship with the SriO3 substrate.

• 한국결정성장학회지
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• 제8권2호
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• pp.286-291
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• 1998

$RuO_2$를 하부 전극으로 적용하여 스퍼터링 가스의 주입비($Ar/O_2$ratio) 변화에 따른 $SrTiO_3$ 박막의 물성을 고찰하였다. 플라스마 가스내 $Ar/O_2$비 변화가 결정성, 표면 morphology등의 $SrTiO_3$ 박막의 미세구조에 큰 영향을 미치는 것을 확인할 수 있었다. 플라스마 가스내의 산소량이 증가함에 따라 박막의 표면 morpholgy 및 상형성의 향상을 통하여 $SrTiO_3$박막의 전기적 특성을 개선할 수 있음을 관찰하였다. 산소의 양이 증가할수록 ST 박막의 누설전류는 $2.0{\times}10^{-6}A/{\textrm}{cm}^2(Ar/O_2=10/0)$에서 $3.8{\times}10^{-7}A/{\textrm}cm^2(Ar/O_2=5/5)$로 감소하였고, 유전 상수값은 $70(Ar/O_2=10/0)$에서 $190(Ar/O_2=5/5)$으로 증가하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 전문대학교육위원 P
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• pp.31-34
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• 1999

In the present study, we fabricated stoichiometric $(Ba_{1-x}Sr_x)TiO_3$ thin films at various substrate temperature and contents using of magnetron sputtering method on optimized Pt-based electrodes (Pt/TiN/$SiO_2$/Si). The substate temperature deposited at 200[ $^{\circ}C$], 400[$^{\circ}C$] and 600[$^{\circ}C$] and crystalline BST thin films show above 400[$^{\circ}C$]. Also, the composition of $(Ba_{1-x}Sr_x)TiO_3$ thin films deposited on Si wafer substrate at 400[$^{\circ}C$] were closed to stoichiometry($1.015{\sim}1.093$ in A/B ratio), but compositional deviation from a stoichiometry is larger as $SrCO_3$ is added. The drastic decrease of dielectric constant and increase of dielectric loss in $(Ba_{1-x}Sr_x)TiO_3$thin films is observed above 100[kHz]. V-I characteristics of $(Ba_{1-x}Sr_x)TiO_3$ thin films show the decrease of leakage current with the increase of $SrCO_3$ contents.

• 한국전기전자재료학회논문지
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• 제15권11호
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• pp.933-938
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• 2002

(Ba,Sr)TiO$_{4}$ (BST) thin films on Pt/Ti/SiO$_{2}$/Si substrates were deposited by a sol-gel method and the etch characteristics of BST thin films have been investigated as a function of gas mixing ratio. The maximum etch rate of the BST films was 440 $AA$/min under such conditions as: CF$_{4}$(CF$_{4}$＋Ar) of 0.2, RF-power of 700 W, DC-bias voltage of -200 V, pressure of 15 mTorr and substrate temperature of 30 $^{circ}C$. The selectivities of BST to Pt, SiO$_{2}$ and PR were 0.38, 0.25 and 0.09, respectively. In the XPS (X-ray photoelectron spectroscopy) analysis, Barium (Ba) and Strontium (Sr) component in BST thin films formed low volatile compounds such as BaFx, SrFx, which are forms by the chemical reaction with F atoms and is removed by Ar ion bombardment. Titanium (Ti) is removed by chemical reaction such as TiF with ease. The result of secondary ion mass spectrometry (SIMS) analysis confirmed the existence of the BaFx, SrFK, TiFx.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.73-76
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• 2001

We deposited epitaxial $Ba_{0.6}$S $r_{0.4}$Ti $O_3$(BST) films having thickness of 400 nm on MgO(001) substrates, where a 10 nm thick $Ba_{1-x}$S $r_{x}$Ti $O_3$(x=0.1-0.7) interlayer was inserted between BST and MgO to manipulate the stress of the BST films. Since the main difference of those epitaxial BST films was the lattice constant of the interlayers, we were very successful in controlling the stress of the BST films. BST films under small tensile stress showed larger dielectric constant than that without stress as well as those under compressive stress. Stress relaxation was investigated using epitaxial BST films with various thicknesses grown on different interlayers. For BST films grown on $Ba_{0.7}$S $r_{0.3}$Ti $O_3$ interlayers, the critical thickness was about 600 nm. On the other hand, the critical thickness of single-layer BST film was less than 100 nm.00 nm.m.m.m.