• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.313-322
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• 2001

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. Rosette and pyrochlore phase are observed in PLZT (10/40/60) thin film and the (100) orientation, the grain size, and the surface roughness of PLZT thin films increase due to the increase of Ti amount in Zr/Ti concentration ratio. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10KHz decrease from 600 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kY/cm decrease from 1.64$\times$10$^{-6}$ to 1.26$\times$10$^{-7}$ A/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$ 170 ㎸/cm, the remanent polarization and the coercive field increase from 6.62 to 12.86 $\mu$C/$\textrm{cm}^2$ and from 32.15 to 56.45 ㎸/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying 10$^{9}$ square pulses with $\pm$5V, the remanent polarization of the PLZT (10/40/60) thin film decreases 50％ from the initial state while that of the PLZT (10/0/100) thin film decreases 30％. In the results of retention measurements of 10$^{5}$ s, the remanent polarization of the PLZT (10/0/100) thin film decreases only 11％ from the initial state, while that of the PLZT (10/40/60) thin film decreases 40%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.7-14
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• 2000

A Bi$_{4}$Ti$_{3}$O$_{12}$ (BIT) thin film is prepared by sol-gel method using acetate precursors and evaluated whether it could be applied to NVFRAM (Non-Volatile Ferroelectric RAM). The drying and the annealing temperature are 40$0^{\circ}C$ and $650^{\circ}C$, respectively and they are determined from the DT-TG (Differential Thermal-Thermal Gravimetric) analysis. The BIT thin film deposited on Pt/Ta/SiO$_{2}$/Si substrate shows orthorhombic perovskite phase. The grain size and the surface roughness are about 100 nm and 70.2$\AA$, respectively. The dielectric constant and the loss tangent at 10 KHz are 176 and 0.038, respectively, and the leakage current density at 100 ㎸/cm is 4.71 $mutextrm{A}$/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$250 ㎸/cm, the remanent polarization (Pt) and the coercive field (Ec) are 5.92 $\mu$C/$\textrm{cm}^2$ and 86.3 ㎸/cm, respectively. After applying 10$^{9}$ square pulses of $\pm$5V, the remanent polarization of the BIT thin film decreases as much as about 33% from 5.92 $\mu$C/$\textrm{cm}^2$ of initial state to 3.95 $\mu$C/$\textrm{cm}^2$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1066-1072
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• 2005

The effects of La concentration in PLZT (z/30/70) thin film prepared by sol-gel method are investigated for the NVFRAM application. As the La concentration increases, the dielectric constants at 10 kHz increase from 450 to 600, while the loss tangent and the leakage current density at 100 kV/cm decrease from 0.075 to 0.025 and from $5.83{\times}10^{-7}\;to\;1.38{\times}10^{-7}\;A/cm^2,$ respectively. In the results of hysteresis loops measured at 175 kV/cm, the remanent polarization and the coercive field decrease from 20.8 to $10.5{\mu}C/cm^2$ and from 54.48 to 32.12 kV/cm, respectively, with the increase of La concentration from 0 to $10mol\%.$ After applying for $10^9$ cycles of square pulses with ${\pm}5V$ height, the remanent polarization of the PLZT (10/30/70) thin film decreases $40\%$ from the initial state, while that of the PLZT (10/30/70) thin film decreases $64\%.$.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.28-31
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• 2000

In this paper, the effects of La addition of PLZT(x/30/70) thin films Prepared by sol-gel method are investigated for NVFRAM application. The tetragonality (c/a), the grain size, and the surface roughness of PLZT thin films decrease with an increase of La concentration. As the La concentration increases, the dielectric constants at 10 kHz increase from 450 to 600, while the loss tangent decrease from 0.075 to 0.025. Also, the leakage current density at 100kV/cm decrease from 5.83$\times$10$^{-7}$ to 1.38$\times$10$^{-7}$ 4/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$170kV/cm, the remanent polarization and the coercive field of PLZT thin films with La concentration from 0 to 10㏖％ decrease from 20.8 to 10.5 $\mu$C/cm and from 54.48 to 32.12kV/cm, respectively. After a fatigue measurement by applying 10$^{9}$ square pulses with $\pm$5V, the remanent polarizations of PLZT thin films with 0 and 10㏖％ La concentration decrease about 64 and 42 ％ from initial state. In the results of retention measurement after 10$^{5}$ s, PLZT thin films with 0 to 10mo1％ La concentration show that the remanent polarization is decreased about 43％ and 9％ from initial state, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.1-1
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• 2001

비휘발성 메모리 소자로의 응용의 관점에서, sol-gel 방법으로 La 을 10mo1% 로 고정시킨 PLZT (10/y/z) 박막을 제작하여 Zr/Ti 조성비에 따른 구조적 및 전기적 특성을 조사하였다. PLZT(10/40/60) 박막은 로제트와 파이로클로르 상이 관찰되었으며, Zr/Ti 조성비에서 Ti 함유량이 증가함에 따라, (100) 배향성, 결정립 크기와 표면 거칠기는 증가되었다. 또한 Zr/Ti 조성비에서 Ti 함유량이 증가함에 따라, 10㎑ 에서 비유전율은 600 에서 400 으로 감소된 반면, 유전손실은 0.028 에서 0.053 로 증가되었으며, 170 ㎸/cm 에서 누설전류밀도는 1.64×$10^{-6}$ 에서 1.26×$10^{-7}$A/㎠ 으로 감소되었다. 그리고 ± 170㎸/㎝ 에서 측정한 PLZT 박막의 이력곡선을 측정한 결과, Zr/Ti 조성비가 40/60 에서 0/100 로 변화함에 따라 PLZT 박막의 잔류분극과 항전계는 6.62 에서 12.86 μC/cm2, 32.15 에서 56.45㎸/㎝ 로 각각 증가되었으며, 피로와 retention 특성 역시 개선되었다. PLZT 박막에 ±5V 의 사각펄스를 $10^9$ 회 인가하여 피로특성을 측정한 결과, PLZT(10/40/60) 박막의 잔류분극은 초기분극값으로부터 50% 감소된 반면, PLZT(10/0/100) 박막은 30% 감소되었다. 또, $10^5$ 초의 retention 결과에서 PLZT(10/0/100) 박막은 초기분극값에서 오직 11% 만이 감소된 반면, PLZT(10/40/60) 박막은 40% 감소되었다.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.195-198
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• 1999

A Bi$_4$Ti$_3$O$_{12}$ (BIT) thin film is prepared by sol-gel method using acetate precursors and evaluated whether it could be applied to NVFRAM. The drying and the annealing temperature are 40$0^{\circ}C$ and $650^{\circ}C$, respectively and they are determined from the DT-TG analysis. The BIT thin film deposited on Pt/Ta/SiO$_2$/Si substrate shows orthorhombic perovskite phase. The grain size and the surface roughness are about 100 nm and 70.2$\AA$, respectively. The dielectric constant and the loss tangent at 10 KHz are 176 and 0.038, respectively, and the leakage current density at 100㎸/cm is 4.71$mutextrm{A}$/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$250㎸/cm, the remanent polarization (Pr) and the coercive field (Ec) are 5.92$mutextrm{A}$/$\textrm{cm}^2$ and 86.3㎸/cm, respectively. After applying 10$^{9}$ square pulses of $\pm$5V, the remanent polarization of the BIT thin film decreases as much as about 33% from 5.92 $\mu$C/$\textrm{cm}^2$ of initial state to 3.95 $\mu$C/$\textrm{cm}^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.320-321
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• 2008

Ferroelectric $SrBi_2Ta_2O_9$(SBT) ceramics were deposite on Pt/Ti/SiO2/Si substrates using a sintered SBT target and then were annealed in the oxygen atmosphere at $750^{\circ}C$, the most excellent characteristics were shown, and the remnant polarization ($2P_r$) value and the coercive electric field ($E_c$) were respectively about 12.40[${\mu}C/cm^2$] and 30[kV/cm]. Moreover, the excellent fatigue characteristic t was little aged even after $10^{10}$ cycles of switchings. The leakage current density and the dielectric constant of the SBT capacitor annealed in the oxygen atmosphere were respectively approximately $2.13\times10^{-9}$ [A/$cm^2$] and 340.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.1
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• pp.29-37
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• 1999

In this study, we have prepared PLT thin films having various La concentrations by using sol-gel method and studied on the effect of La concentration on the electrical properties of PLT thin films. As the La concentration increases from 5mol% to 28mol%, the dielectric constant at 10kHz increases from 428 to 761, while the loss tangent decreases from 0.063 to 0.024. Also, the leakage current density at 150kV/cm has a tendency to decrease from 6.96${\mu}A/cm^2$ to 0.79${\mu}A/cm^2$. In the result of hysteresis loops of PLT thin films, the remanent polariation and the coercive field decrease from 9.55${\mu}C/cm^2$ to 1.10${\mu}C/cm^2$ and from 46.4kV/cm to 13.7kV/cm, respectively. With the result of the fatigue test on the PLT thin films, we have found that the fatigue properties are improved remarkably as the La concentration increases from 5 mol% to 28mol%. In particular, the PLT28) has paraelectric phase and its charge storage clensity and leakage current density at 5V are 134fC/${\mu}cm^2$ and 1.01${\mu}A/cm^2$, respectively. The remanent polarization and coercive field of the PLT(10) film are 6.96${\mu}C/cm^2$ and 40.2kV/cm, respectively. After applying of $10^9$ square pulses with ${\pm}5V$, the remanent polarilzation of the PLT(10) film decreases about 20% from the initial state. In the results, we conclude that the 10mol% and the 28mol% La doped PLT thin films are very suitable for the capacitor dielectrics of new generation of DRAM and NVFRAM respecitively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.609-615
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• 2005

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10 kHz decrease from 550 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kV/cm decrease from $1.64\times10^{-6}$ to $1.26\times10^{-7}\;A/cm^2$. In the results of hysteresis loops measured at $\pm170kV/cm$, the remanent polarization and the coercive field increase from 6.62 to $12.86{\mu}C/cm^2$ and from 32.15 to 56.45 kV/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying $10^9$ square pulses with $\pm5V$, the remanent polarization of the PLZT (10/40/60) thin film decreases $50\%$ from the initial state while that of the PLZT (10/0/100) thin film decreases $28\%$. In the results of retention measurements of 10s s, the remanent polarization of the PLZT (10/0/100) thin film dec.eases only $10\%$ from the initial state, while that of the PLZT (10/40/60) thin film decreases $40\%$.