• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권12호
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• pp.549-554
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• 2006

In this paper we first applied the chemical mechanical polishing (CMP) process to the planarization of ferroelectric film in order to obtain a good planarity between electrode and ferroelectric film. $Pb_{1.1}(Zr_{0.52}Ti_{0.48})O_3$ (shortly PZT) ferroelectric film was fabricated by the sol-gel method. And then, we compared the structural characteristics before and after CMP process of PZT films. Removal rate, WIWNU% and surface roughness have been found to depend on slurry abrasive types and their hardness, especially, surface roughness and planarity were strongly depends on its pH value. A maximum in the removal rate is observed in the silica slurry, in contrast with the minimum removal rate occurs at ceria slurry. We found that the surface roughness of PZT films can be significantly reduced using the CMP technique.

• 한국세라믹학회지
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• 제32권7호
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• pp.783-792
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• 1995

Sol-Gel derived ferroelectric PZT thin films were fabricated on ITO/Glass and Si/SiO2 substrates. In order to investigate the effect of catalysts on the densification and crystallization of PZT thin films, a nitric acid or ammonium hydroxide was added to the PZT stock solution at the state of partial hydrolysis reaction. The measured pH for a stable PZT sol was 5.2~9.3. In case of an acid-catalyzed PZT sol, a highly condensed particulate PZT sol was formed by accelerating the hydrolysis reaction. But weakly branched polymeric PZT sol was formed with a base-catalyzed condition. The difference in densification behavior was not found in the pH range of added catalyst, but the refractive index of PZT thin film was increased rapidly as the annealing temperature increased. The PZT thin film annealed at 54$0^{\circ}C$ for 10 min was fully densified and its refractive index was above 2.4. When the annealing temperature increased, the transition from the pyrochlore phase to perovskite appeared at 54$0^{\circ}C$. The base-catalyzed PZT thin film suppressed to form the pyrochlore phase and proceeded effectively to convert the perovskite phase. This was due to the formation of polymeric molecular structure by controlling the hydrolysis and condensation reaction through the additiion of the ammonium hydroxide.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.110-115
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• 2000

$SrBi_2Ta_2O_9$ thin films were deposited at room temperature on the usual (111) oriented Pt bottom electrodes using r.f. magnetron sputtering, and then post-annealed at 650-$800^{\circ}C$ for 30min in oxygen flow. Low temperature processing which shows the preferred oriented SBT thin films was obtained by controlling the sputtering pressure and/or Sr content in target. The orientation and grain growth behavior of SBT thin films were dependent on Sr contents in films. With increasing the excess Bi content up to 50% in SBT thin films, it was possible to lower the onset temperature of grain growth. The c-axis preferred oriented SBT thin films were well-grown under the condition of low post-annealing($650^{\circ}C$) by lowering post-annealing pressure. After $10^{11}$ switching cycles, no polarization degradation was observed in both preferred oriented SBT capacitors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.170-173
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• 2001

Thin films of phase-pure perovskite (P $b_{0.72}$L $a_{0.28}$) $Ti_{0.93}$ $O_3$(PLT) were deposited in-situ onto Pt/Ti/ $SiO_2$/Si substrates by pulsed laser deposition. We have systematically investigated the variation of grain sizes depending on the process condition. Both in-situ annealing and ex-situ annealing treatments have been compared depending on the annealing time. Two-step process to grow (P $b_{0.72}$L $a_{0.28}$) $Ti_{0.93}$ $O_3$(PLT) films was adopted and verified to be useful to enlarge the grain size of the film and to enhance the leakage current characteristics. The grain sizes of PLT thin films were successfully controlled 260 to 350 nm by changing process parameters. Electrical properties including dielectric constant, ferroelectric characteristics, crystallization and leakage current of PLT thin films were shown to be strongly inf1uenced by grain size. Also PLT thin films on p-type(100) Si substrate will be fabricated by pulsed laser deposition technique using a Nd:YAG laser with different wavelengths of 355, 532 and 1064 nm. Effect of the variation of laser wavelength on dielectric properties will be discussed. Microstructural and electrical properties of the film were investigated by C-V measurement leakage current measurement and SEM.ent and SEM.

• 대한전자공학회논문지
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• 제26권7호
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• pp.83-89
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• 1989

강유전성 $PbTiO_3$ 박막을 rf스터링으로 기판온도 $100{\sim}150^{\circ}C$에서 형성시켰다. 이 박막의 구조는 X선 회절결과 비정질 형태로 파이로클로어 구조를 갖고 있었다. 이 박막을 열에 의해 어닐링한 경우는 $550^{\circ}C$에서, 레이저의 주사로 어닐링한 경우는 레이저 출력이 50watts일때 가장 우수한 결정 구조를 구할 수 있었다. 집합에서의 계면 특성을 구하기 위하여 MFS(metal-ferroelectric-semiconductor)및 MFOS(metal-ferroelectric-oxide-semiconductor) 구조를 형성하여 C-V특성을 조사하였다. 이때 MFS보다 MFOS의 경우가 Si표면에 sputter에 의한 결함이 작음을 알 수 있었다.

• 한국세라믹학회지
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• 제40권12호
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• pp.1189-1196
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• 2003

Sol-gel법으로 강유전성 B $i_{3.25}$L $a_{0.75}$ $Ti_3$ $O_{12}$ (BLT) stock solution을 합성하고 Pt/Ti $O_2$/ $SiO_2$/Si 기판위에 스핀코팅법으로 BLT 박막을 증착하였다. 본 실험에서는 Bi(TMHD)$_3$, La(III)2-Methoxyethoxide, Ti(IV)i-propoxide를 출발물질로 사용하였으며 2-Methoxyethanol을 용매로 사용하였다. 급속열처리(RTA)가 BLT 박막의 결정성장을 촉진시키기 위해 사용되었고, RTA를 실시한 시편과 RTA를 실시하지 않은 시편의 전기적 특성을 비교하였다. RTA를 실시한 후 72$0^{\circ}C$에서 로 열처리 한 BLT 박막의 경우 5V 인가 전압 하에서 2Pr 값은 RTA를 실시하지 않은 경우보다 27% 증가한 20.46$\mu$C/$ extrm{cm}^2$이었다.

• 한국세라믹학회지
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• 제41권1호
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• pp.13-18
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• 2004

$La_{0.5}Sr_{0.5}CoO_3$ (LSCO) electrodes were prepared on ferroelectric $Sr_{0.9}Bi_{2.1}Ta_2O_9$(SBT) thin films by spin coating method using photosensitive sol-gel solution. Self-patterning technique of photosensitive sol-gel solution has advantages such as simple manufacturing process compared to photoresist/dry etching process. Lanthanum(III) 2-methoxyethoxide, Stronitium diethoxide. Cobalu(II)2-methoxyethoxide were used as starting materials for LSCO electrode. UV irradiation on LSCO thin films lead to decrease solubility by M-O-M bond formation and the solubility difference allows us to obtain self-patternine. There was little composition change of the LSCO thin films between before leaching and after leaching in 2-methoxyethanol. The lowest resistivity of LSCO thin films deposited on $SiO_2$/Si substrate was $1.1{\times}10^{-2}{\Omega}cm$ when the thin film was ennealed at $740^{\circ}C$. The values of Pr/Ps and 2Pr of LSCO/SBT/Pt capacitor on the applied voltage of 5V were 0.51, 8.89 ${\mu}C/cm^2$, respectively.

• 한국세라믹학회지
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• 제45권6호
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• pp.358-362
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• 2008

$BiFeO_3$ films were hetero-epitaxially grown on $SrTiO_3$ substrate with a various orientation by pulse laser deposition. $BiFeO_3$ films grown on (111) $SrTiO_3$ substrate have a rhombohedral structure, identical to that of single crystals. On the other hand, films grown on (110) or (001) $SrTiO_3$ substrate are monoclinically distorted from the rhombohedral structure due to the epitaxial constraint. The easy axis of spontaneous polarization is close to [111] for the variously oriented films. Dramatically enhanced polarization and magnetization have been found for $BiFeO_3$ thin films grown on $SrTiO_3$ substrate comparing to that of $BiFeO_3$ crystals. The results are explained in terms of an epitaxially-induced transition between cycloidal and homogeneous spin states, via magneto-electric interactions.

• 한국진공학회지
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• 제8권3A호
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• pp.224-230
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• 1999

$SrBi_{2x}Ta_2O_9$ (SBT) thin films were prepared on platinized silicon substrates by MOD process, and their ferroelectric and leakage current characteristics were investigated. The grain size of the MOD derived SBT films increased with increasing the BI/Ta mole ration. Although the SBT films with x of 0.8~1.2 were composed of the equiaxed grains, the elongated grains were also observed for the SBT films with x of 1.4 and 1.6. The SBT film with x of 1.2 exhibited the optimum ferroelectric properties of 2PR : 9.79 $\muC/\textrm{cm}^2$ and Ec : 24.2kV/cm at applied voltage of 5V. The leakage current density of the SBT films increased with increasing the BI/Ta mole ratio. With post annealing process, 2Pr and $E_c$of the SBT film with x of 1.2 increases 11.3 $\muC/\textrm{cm}^2$ and 39.6kV/cm, respectively. decrement of the leakage current density by post annealing process increased remarkably with increasing the Bi/ta mole ratio, and the SBT film with x=1.6 exhibited the lowest leakage current density after post annealing process.

• E2M - 전기 전자와 첨단 소재
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• 제9권3호
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• pp.251-258
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• 1996

Sol-Gel derived ferroelectric Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_{3}$ thin films have been fabricated on Pt/Ti/ $SiO_{2}$/Si substrate. Two kinds of fast annealing methods, F-I (six times of intermediate and final annealing) and F-II(one final annealing after six times of intermediate annealing) were used for preparation of multi-coated PZT thin films. As the annealing temperature was increased, high capacitance could be obtained, for instance, 2700.angs.-thick PZT thin film annealed at 680.deg. C had a capacitance value of approximately 20nF at 1kHz. In addition, it is found that the dielectric constant is a function of the perovskite phase fraction. In case of F-I method, PZT thin film had a remanent polarization(Pr) of 8-15.mu.C/c $m^{2}$ and a coercive field( $E_{c}$) of 35-44kV/cm according to annealing temperature, whereas PZT film fabricated by F-II method had as high as 24-25.mu.C/c $m^{2}$ and 48-59kV/cm, respectively. As a result of measuring Curie temperature, PZT thin film had a range of 460-480.deg. C by F-I method and more or less higher range of 525-530.deg. C by F-II method, which implied that different microstructures could cause the different Curie temperature. Through I-V measurement, leakage current of PZT thin film fabricated by F-I and F-II methods was 64nA/c $m^{2}$ and 2.2.mu.A/c $m^{2}$ in the electric field of 100kV/cm, respectively.y.y.y.