• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.851-856
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• 2003

We have investigated the material and electrical properties of $Bi_{4-x}La_xTi_3O_{12}$ (BLT) ferroelectric thin film for ferroelectric nonvolatile memory applications of capacitor type and single transistor type. The 120nm thick BLT films were deposited on $Pt/Ti/SiO_2/Si$ and $SiO_2/Nitride/SiO_2$ (ONO) substrates by the sol-gel spin coating method and were annealed at $700^{\circ}C$. It was observed that the crystallographic orientation of BLT thin films were strongly affected by the excess Bi content and the intermediate rapid thermal annealing (RTA) treatment conditions regardeless of two type substrates. However, the surface microstructure and roughness of BLT films showed dependence of two different type substrates with orientation of (111) plane and amorphous phase. As increase excess Bi content, the crystallographic orientation of the BLT films varied drastically in BLT films and exhibited well-crystallized phase. Also, the conversion of crystallographic orientation at intermediate RTA temperature of above $450^{\circ}C$ started to be observed in BLT thin films with above excess 6.5% Bi content and the rms roughness of films is decreased. We found that the electrical properties of BLT films such as the P-V hysteresis loop and leakage current were effectively modulated by the crystallographic orientations change of thin films.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.574-577
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• 2002

In recent year, BLT$(Bi_{3.25}La_{0.75}Ti_3O_{12})$ has been one of promising substitute materials at the ferroelectric random access memory applications. We manufactured $(Bi_{3.25}La_{0.75}Ti_3O_{12})$ Target with a ceramic process. The BLT target was sintered at $1100^{\circ}C$ for 4 hours. Using RF magnetron sputtering, a deposited BLT thin films were estimated about ferroelectric property as a functions of post annealing time. The BLT thin films showed a promoted ferroelectric characteristics at the post annealied sample for 30 minutes. This sample exhibited the (117) preferred crystal orientation, current density of $2{\times}10^{-8}A/cm^2$, a remanent polarization of $10{\mu}C/cm^2$ and a coercive field of 62.1 KV/cm respectively.

• 한국전기전자재료학회논문지
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• 제15권9호
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• pp.783-787
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• 2002

In recent year, B $i_{4-}$x L $a_{x}$ $Ti_3$ $O_{12(BLT)}$ is one of promising substitute materials for the ferroelectric random access memory(FRAM) applications. But the systematic composition is still insufficient, so this experiment was carried out in ceramic ambient sintering process which has the very excellent ferroelectric property. Samples were prepared by a bulk and the purpose which was estimated with a suitability of thin films applications. The density of B $i_{3.75}$ L $a_{0.25}$ $Ti_3$ $O_{12}$ was high and the XRD pattern showed that the intensity of main peak (117) was increased at the argon ambient sintering. Controlling the quantity of oxygen, crystallization showed a thin, long plate like type, and we obtained the excellent dielectric and polarization properties at the argon atmosphere sintering. Also this sintering process was effective at the bulk sample. Argon ambient sintered sample produced higher permittivity of 154, the remanent polarization(2Pr) of 6.8 uC/$\textrm{cm}^2$ compared with that sintered in air and oxygen ambient. And this sintering process showed a possibility which could be applied to thin films process..

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.192-193
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• 2006

A 16Mb ITIC FeRAM device was fabricated with BLT capacitors. The average value of the switchable 2 polarization obtained m the 32k-array (unit capacitor size: 068 ${mu}m^2$) capacitors was about 16 ${\mu}C/cm^2$ at 3V and the uniformity within an 8-inch wafer was about 2.8%. But a lot of cells were failed randomly during the measuring the bit-line signal of each cell. It was revealed that the Grain size and orientation of the BLT thin film were severely non-uniform. Therefore, the uniformity of the grain size and orientation was improved by changing the process conditions of post heat treatment. The temperature of nucleation step was the very effective on varying the microstructure of the BLT thin film. The optimized temperature of the nucleation step was $560^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제15권6호
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• pp.486-491
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• 2002

We have fabricated $Bi_{3.25}La_{0.75}Ti_3O_12$ (BLT) thin films on the Pt/Ti/$SiO_2$/Si substrates using a metalorganic decomposition (MOD) method with annealing temperature from $550^{\circ}C$ to $750^{\circ}C$. The structural properties of BLT films examined by x-ray diffraction (XRD). From XRD analysis. BLT thin films show polycrystalline structure. The layered-perovskite phase was obtained by spin-on films at above $600^{\circ}C$ for 1h. Scanning electron microscopy (SEM) showed uniform surface composed of rodlike grains. The grain size of BLT films increased with increasing annealing temperature. The BLT film annealed at $650^{\circ}C$ was measured to have a dielectric constant of 279, dielectric loss of 1.85(%), remanent polarization of $25.66\mu C/\textrm{cm}^2$, and coercive field of 84.75 kV/cm. The BLT thin films showed little polarization fatigue test up to $3.5{\times}10^9$ bipolar cycling at 5 V and 100 kHz.

• 한국전기전자재료학회논문지
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• 제16권5호
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• pp.378-384
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• 2003

Etching species in CF$_4$/Ar plasma and the behavior of etching rate of Bi$_4$-$_{x}$L$_{x}$rTi$_3$O$_2$ (BLT) films were investigated in inductively coupled plasma (ICP) reactor in terms of etch parameters. The etching rate as functions of CF$_4$ contents showed the maximum 803 $\AA$/min at 20% CF$_4$ addition in CF$_4$/Ar plasma. The increase of RF power and DC bias voltage caused to an increase of etch rate. The variation of relative volume densities for F and he atoms were measured with the optical emission spectroscopy (OES). The chemical states of BLT were investigated with using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that La-fluorides remained on the etched surface. The presence of maximum etch rate at CF$_4$(20%)/Ar(80%) may be explained by the concurrence of two etching mechanisms such as physical sputtering and chemical reaction. The roles of he ion bombardment include destruction of metal (Bi, La, Ti)-O bonds as well as assistant for chemical reaction of metals with fluorine atoms.oms.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.565-568
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• 2001

We have fabricated $Bi_{3.25}La_{0.75}Ti_{3}O_{12}(BLT)$ thin(200nm) films on the $Pt/Ti/SiO_{2}/Si$ substrates using a MOD(Metalorganic decomposition) method with annealing temperature from $550^{\circ}C$ to $750^{\circ}C$. The structural properties of the films examined by x-ray diffraction. The layered-perovskite phase obtained above $600^{\circ}C$. Scanning electron micrographs showed uniform surface composed of rodlike grains. The grain size increased with increasing annealing temperature. The BLT thin films showed little polarization fatigue test up to $3.5{\times}10^{9}$ bipolar cycling at a 5V and 100kHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.565-568
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• 2001

We have fabricated $Bi_{3.25}$$La_{0.75}$ti$_3$O$_{12}$ (BLT) thin(200nm) films on the Pt/Ti/SiO$_2$/Si substrates using a MOD(Metalorganic decomposition) method with annealing temperature from 55$0^{\circ}C$ to 75$0^{\circ}C$. The structural properties of the films examined by x-ray diffraction. The layered-perovskite phase obtained above $600^{\circ}C$. Scanning electron micrographs showed uniform surface composed of rodlike grains. The grain size increased with increasing annealing temperature. The BLT thin films showed little polarization fatigue test up to 3.5x10$^{9}$ bipolar cycling at a 5V and 100kHz.kHz.

• 마이크로전자및패키징학회지
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• 제10권2호
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• pp.7-12
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• 2003

졸-겔(Sol-Gel)법으로 $SiO_2/Si$ 기판 위에 $Bi_{3.3}La_{0.7}O_{12}$(BLT) 강유전체 박막을 스핀코팅하여 Metal-Ferroelectric-Insulator-Silicon 구조의 캐패시터 소자를 제작하였다. 열처리하지 않은 BLT 박막시료를 $650^{\circ}C$와 $700^{\circ}C$의 온도에서 열처리함으로서 임의 배향을 가지는 퍼롭스카이트 결정구조를 나타내었다. 열처리 온도를 $650^{\circ}C$에서 $700^{\circ}C$로 증가시킴에 따라서 (117) 주피크의 full width at half maximum(FWHM)값이 약 $0.65^{\circ}$에서 $0.53^{\circ}$로 감소하여 결정성이 개선되었으며 결정립 크기와 $R_rms$ 값이 증가하면서 박막표면이 거칠어지는 경향을 보여주었다. $700^{\circ}C$에서 열처리한 BLT 박막시료에 대해 인가 전압에 따른 정전용량(C-V)값을 측정한 결과 5V의 인가전압에서 메모리 원도우 값이 약 0.7V를 보여주었으며, 3V의 인가전압에서 누설전류 값이 약 $3.1{\times}10^{-8}A/cm^2$을 나타내었다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.173-176
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• 2002

B $i_{3.3}$L $a_{0.7}$ $Ti_{3}$ $O_{12}$(BLT) 강유전체 박막을 Pt/Ti/ $SiO_2$/Si 기판위에 졸-겔법 (sol-gel method) 으로 스핀코팅하여 Metal-Ferroelectric-Metal(MFM) 구조의 커패시터를 형성하였다. BLT 박막의 결정성은 후속열처리 온도가 증가할수록 향상되었으며 $R_{근}$값은 as~coated된 BLT 박막의 경우 3.8$\AA$를 나타내었으나 열처리 온도를 $700^{\circ}C$로 증가한 경우 12.9$\AA$으로 거칠은 표면형상으로 변화되었다. $650^{\circ}C$로 열처리된 BLT 박막의 잔류분극 2Pr ($\pm$($P^{*}$ -$P^{ ^}$))값은 5V 인가전압에서 약 29.1 $\mu$C/$cm^2$을 나타내었다. 또한 $10^{10}$ 스위칭 cycles 가지 분극 스위칭을 반복한 후에도 뚜렷한 잔류분극의 변화를 발견할 수 없어서 우수한 피로특성을 나타내었다. 3V 전압에서 BLT 박막의 누설전류는 약 2.2$\times$$10^{-8}$ A/$cm^2$를 나타내었다.내었다.었다.