• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.137-137
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• 2006

본 연구에서는 FeRAM 적용을 위한 BLT 캐패시터 제조시 CMP 공정압력 변화에 따른 Leakage Current의 특성에 대해서 연구하였다. 6-inch Pt/Ti/Si 웨이퍼를 사용하였으며, 기판 위에 졸-겔(Sol-Gel)법으로 모든 BLT를 스핀코팅을 이용하여 증착시켰다. 증착된 BLT는 $200^{\circ}C$에서 기본 열처리 후 다시 $700^{\circ}C$에서 후속 열처리 하였다. 이러한 과정을 두번 반복하였며, FeRAM 적용을 위한 BLT 캐패시터 제조시 CMP 공정 중 압력 변화를 달리하여 BLT 캐패시터를 제조한 후 Leakage Current를 측정하였다. 결과적으로 CMP 공정 시 압력의 증가에 따라 Leakage Current값이 증가하였다. CMP 공정시 압력과 박막 표면의 스크레치로 증가로 인해 Leakage Current의 증가하였다고 판단된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.865-870
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• 2003

The MFIS (Metal-Ferroelectric-Insulator-Semiconductor) capacitors were fabricated using a metalorganic decomposition method. Thin layers of CeO$_2$ were deposited as a buffer layer on Si substrate and BLT thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated. X -ray diffraction was used to determine the phase of the BLT thin films and the quality of the CeO$_2$ layer. The morphology of films and the interface structures of the BLT and the CeO$_2$ layers were investigated by scanning electron microscopy. The width of the memory window in the C-V curves for the MFIS structure is 2.82 V. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory FETs with large memory window.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.305-309
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• 2002

We have successfully fabricated a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure using Bi$\sub$4-x/La$\sub$x/Ti$_3$O$\sub$12/ (BLT) ferroelectric thin film and SiO$_2$/Nitride/SiO$_2$ (ONO) stacked buffer layers for single transistor type ferroelectric nonvolatile memory applications. BLT films were deposited on 15 nm-thick ONO buffer layer by sol-gel spin-coating. The dielectric constant and the leakage current density of prepared ONO film were measured to be 5.6 and 1.0 x 10$\^$-8/ A/$\textrm{cm}^2$ at 2MV/cm, respectively, It was interesting to note that the crystallographic orientations of BLT thin films were strongly effected by pre-bake temperatures. X-ray diffraction patterns showed that (117) crystallites were mainly detected in the BLT film if pre-baked below 400$^{\circ}C$. Whereas, for the films pre-baked above 500$^{\circ}C$, the crystallites with preferred c-axis orientation were mainly detected. From the C-V measurement of the MFIS capacitor with c-axis oriented BLT films, the memory window of 0.6 V was obtained at a voltage sweep of ${\pm}$8 V, which evidently reflects the ferroelectric memory effect of a BLT/ONO/Si structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.371-374
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• 2002

Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/$SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10 % excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of n9 and dielectric loss of 1.85[%]. The BLT thin films showed little polarization fatigue test up to 3.5 x $10^{9}$ bipolar switching cycling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.265-271
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• 2003

Ferroelectric lanthanum-substituted Bi$_4$Ti$_3$O$_{12}$(BLT) thin films were fabricated by spin-coating onto a Pt/Ti/SiO$_2$/Si substrate by metalorganic decomposition technique. The grain size in BLT thin films were prepared with controlled by various drying process. The effect of grain size on the crystallization and ferroelectric properties were investigated by x-ray diffraction and field emission scanning electron microscope. The dependence of crystallization and electrical properties are related to the grain size in BLT thin films with different drying temperature. The remanent polarization of BLT thin film increases with the increasing grain size. The value of 2P$_{r}$ and E$_{c}$ of BLT thin film dried at 45$0^{\circ}C$ were 25.9 $\mu$C/$\textrm{cm}^2$ and 85 kV/cm, respectively. The BLT thin film with larger grain size has better fatigue properties. The fatigue properties revealed that small grained film showed more degradation of switching charge than large grained films.lms.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.186-189
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• 2003

The MFIS capacitors were fabricated using a metalorganic decomposition method. Thin layers of $ZrO_2$ and $CeO_2$ were deposited as a buffer layer on Si substrate and BLT thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated. X -ray diffraction was used to determine the phase of the BLT thin films and the quality of the $ZrO_2$ and $CeO_2$ layer. AES show no interdiffusion and the formation of amorphous $SiO_2$ layer is suppressed by using the $ZrO_2$ and $CeO_2$ film as buffer layer between the BLT film and Si substrate. The width of the memory window in the C-V curves for the $BLT/ZrO_2/Si$ and $BLT/CeO_2/Si$ structure is 2.94 V and 1.3V, respectively. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory FETs with large memory window.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.174-177
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• 2003

$Cl_2$ 플라즈마를 이용한 BLT 박막의 식각에서 Ar 가스의 첨가에 따른 식각 속도, 선택비 및 식각 형상의 변화에 대하여 관찰하였다. BLT 박막의 식각 속도는 100% Ar 플라즈마에서 100 % $Cl_2$ 플라즈마에서의 식각 속도보다 약 1.5배정도 빨랐으며, 80% Ar/20% $Cl_2$ 조건에서 $503{\AA}/min$ 최대 식각의 최대 시각 속도를 얻었다. RF 전력과 직류 바이어스 전압을 증가함에 따라 식각 속도는 증가하였으며, $Ar/Cl_2$ 플라즈마의 식각 속도가 $Cl_2$ 플라즈마의 식각 속도 보다 높았다. 식각 공정 변수의 변화에 의한 플라즈마 변수가 BLT 식각 속도에 미치는 영향을 관찰하기 위하여 LP(Lanmuir porbe)와 OES(optical emission spectroscopy)분석을 수행하였다. Ar 첨가량이 증감함에 따라 LP 분석에서 전자의 온도는 증가하였으나 전자밀도는 감소하였다. 이는 Ar의 이온화 준위가 Cl 보다 높기 때문에 이온화 윷이 낮아지기 때문으로 판단된다, 또한, OES 분석에서 Ar 첨가량이 증가함에 따라 Cl 원자의 부피 밀도는 감소하였다. Ar 첨가에 의한 BLT 박막의 식각 속도의 변화와 LP 및 OES 분석을 고려하면, BLT 박막은 화학적 식각의 도움을 받는 무리적 식각에 의하여 식각됨을 확인하였다,

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.87-90
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• 2002

In recent year, BLT($Bi_{3.25}La_{0.75}Ti_{3}O_{12}$) 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 properly as a functions of post annealing temperatures. The BLT thin films showed a promoted ferroelectric characteristics at the post annealied sample of ${700^{\circ}C}$. This sample exhibited the (117) preferred crystal orientation, current density of $3{\times}10^{-8}A/cm^2$, a remanent polarization of $8{\mu}C/cm^2$ and a coercive field of 42.1 KV/cm respectively.