• Korean Journal of Materials Research
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• v.7 no.5
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• pp.381-385
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• 1997

PEMOCVD에 의해서 SrBi$_{2}$Ta$_{2}$O$_{9}$밥막이 낮은 온도에서 성공적으로 Pt/Ti/SiO$_{2}$Si위에 증착되었다. 5$50^{\circ}C$에서 증착된 200nm박막은 치밀하고 작은 결정립을 보였으며 3V의 인가전압하에서 이력곡선은 포화되기 시작하였다. 3V에서 박막은 잔류분극 (P$_{r}$)과 항전계(E$_{c}$)는 각각 15$\mu$/$\textrm{cm}^2$과 50kV/cm이었다. 6V bipolar square pulse의 피로측정에서 박막은 1.0x$10^{11}$cycles까지 피로 현상을 보이지 않았다. PEMOCVD에 의해서 5$50^{\circ}C$에서 증착된 SBT박막은 비휘발성 기억소자에 충분히 활용할 수 있다.다.

• Korean Journal of Materials Research
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• v.7 no.6
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• pp.479-483
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• 1997

Sol-gel법으로 제작한 여러 종류의 Zr/Ti비율을 갖고 있는 PZT박막의 전지적 특성과 신뢰성 특성을 상부 백금 전극을 sputtering으로 증착하고 Ar 기체로 반응성 이온 식각(RIE)방법으로 패턴을 형성한 후 열처리온도의 변화에 따라 조사하였다. Hysteresis loop특성을 되찾게 하였다. Zr/Ti 비율이 감소함에 따라 voltage shift가 증가하였으며 internal field가 없어지는 열처리 온도가 증가하였다. Zr/Ti비율이 감소함에 따라 초기 잔류 분극은 증가하였으나 switching 횟수가 증가됨에 따라 잔류 분극이 급속히 감소하였다.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.290-293
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• 2001

The SrBi$_2$Nb$_2$O$_{9}$ (SBN) thin films were deposited on p-type(100) Si substrates by rf magnetron sputtering to confirm the Possibility of Pt/SBN/Si structure for the application of nondestructive read out ferroelectric random access memory (NDRO- FRAM). The SBN thin films were deposited by co-sputtering method with Sr$_2$Nb$_2$O$_{7}$ (SNO) and Bi$_2$O$_3$ ceramic targets. The SBN thin films deposited at room temperature were annealed at $700^{\circ}C$ for 1hr in $O_2$ ambient. The structural and electrical properties of SBN with different power ratios of targets were measured by x-ray diffraction(XRD), scanning electron microscopy(SEM), capacitance-voltage(C-V), and current-voltage(I-V). The C-V curves of the SBN films showed hysteresis curves of a clockwise rotation showing ferroelectricity. When the Power ratio of the SNO/Bi$_2$O$_3$ targets was 120 W/100 W, the SBN thin films had excellent electrical properties. The memory window of SBN thin film was 1.8 V-6.3 V at applied voltage of 3 V-9 V and the leakage current density was 1.5 $\times$ 10$^{-7}$ A/$\textrm{cm}^2$ at applied voltage of 5 V The composition of SBN thin films was analysed by electron probe X-ray micro analyzer(EPMA) and the atomic ratio of Sr:Bi:Nb with pawer ratio of 120 W/100 W was 1:3:2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.869-873
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• 2004

[ $Sr_xBa_{1-x}Nb_2O_6$ ] (SBN, $0.25{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient, piezoelectric, and a photo refractive properties. In this study, SBN60(x=0.6) thin film was manufactured by ion beam sputtering technique. Using the prepared SBN60 target in $Ar/O_2$ atmosphere as-deposited SBN60 thin film on Pt(100)/$TiO_2/SiO_2/Si$ substrate crystallization and orientation behavior as well as electric properties of SBN60 thin film were examined. SBN60 deposition up to $3000{\AA}$ in thickness, SBN60 thin film was heat-treated at $650^{\circ}C{\sim}800^{\circ}C$. The orientation was shown primarily along (001) plane from XRD pattern where working pressure was $4.3{\times}10^{-4}$ torr. The deposited layer was uniform, preferred orientatin and crystallization behavior resulted in the change of $O_2$ ratio was observed. In electric propertie of Pt/SBN60/Pt thin film capacitor remnant polarization (2Pr) value was $10{\mu}C/cm^2$, the coercive filed (Ec) 50 kV/cm, and the dielectric constant 615, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.1-6
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• 2000

Recently, SrBi$_{2}$Ta$_{2}$ $O_{9}$(SBT) and Pb(Zr,Ti) $O_{3}$(PZT) were much attracted as materials of capacitor for ferroelectric random access memory(FRAM) with higher read/ write speed, lower power consumption and nonvolartility. SBT thin film has appeared as the most prominent fatigue free and low operation voltage. To highly integrate FRAM, SBT thin film has to be etched. A lot of papers have been reported over growth of SBT thin film and its characteristics. However, there are few reports about etching SBT thin film owing to difficult of etching ferroelectric materials. SBT thin film was etched in CF$_{4}$Ar plasma using magnetically enhanced inductively coupled plasma (MEICP) system. In order to investigate the chemical reaction on the etched surface of SBT thin films, X-ray Photoelecton spectrosocpy (XPS) and Secondary ion mass spectroscopy(SIMS) was performed.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.1048-1054
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• 1998

The effects of deposition temperature of Pt top electrodes on the electrical properties of Pb(Zr,Ti))$O_3$, (PZT) thin film were investigated. When the Pt top electrodes were deposited at substrate temperatures of $200^{\circ}C$ or above,the ferroelectric properties of the PZT thin film under the Pt electrode were severely degraded. Whereas those of the PZT film where the Pt electrodes were not deposited were not degraded. Water vapors which remained in the vacuum chamber were dissociated into hydrogen atoms by the catalysis of Pt top electrode, and those hydrogen atoms diffused into the PZT film and produced oxygen vacancies at high substrate temperature, resulting in the degradation of the ferroelectric properties of the PZT film located under the Pt electrode. Since the water vapors could not be dissociated into hydrogen atoms without the catalysis of Pt. the degradation of the PZT film did not take place where the Pt electrode were not deposited. The degraded feroelectric properties could be recovered by rapid thermal annealing (RTA) treatment. On the other hand. leakage current characteristics were improved with increasing the deposition temperature of Pt top electrodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.111-115
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• 2003

200nm 정도의 두께를 가진 SBT 박막이 liquid delivery MOCVD 공정에 의해 (111) oriented Pt/Ti/$SiO_2$/Si 기판 위에 증착되었다 이 실험에서는 $Sr(TMHD)_2$tetraglyme, $Bi(ph)_3$ 그리고 $Ta(O^iPr)_4$(TMHD)를 출발 물질로 사용하였다. Sr 출발 물질의 열적 안정화를 위해서 adduct로 tetraglyme를 사용하여 실험하였고 유기 용매로는 n-butyl acetate를 사용하였다 Substrate temperature와 reactor pressure는 각각 $570^{\circ}C$와 5Torr로 유지시켰다. 또한 vaporizer의 용도는 $190-200^{\circ}C$, 그리고 delivery line 의 온도는 vaporizer 보다 높게 유지 $(220-230^{\circ}C)$하여 출발 용액을 분당 0.1ml로 50분간 주입하였다. 수송가스로 Ar, 산화제로 $O_2$ 가스를 사용하였다. 제조한 SBT 박막은 $750^{\circ}C$에서 열처리한 후 인가전압 3V와 5V에서 $2P_r$값이 각각 6.47, $8.98{\mu}C/cm^2$이었으며, $2E_c$값은 인가전압 3V와 5V에서 각각 2.05, 2.31V이었다 그리고 $800^{\circ}C$에서는$750^{\circ}C$에서 열처리한 SBT 박막보다 다소 우수한 이력특성을 나타내어 $2P_r$ 값은 인가전압 3V와 5V에서 각각 7.59, $10.18{\mu}C/cm^2$ 이었으며, $2E_c$값은 인가 전압 3V와 5V에서 각각 2.00, 2.21V 이었다.

• Korean Journal of Materials Research
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• v.7 no.6
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• pp.505-509
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• 1997

FRAM(Ferroelectric Random Access memory)에의 응용을 위해 rf magnetron sputtering법을 이용하여 SrB $i_{2}$T $a_{2}$ $O_{9}$(SBT)박막을 증착하였다. 사용된 기판은 Pt/Ti/Si $o_{2}$Si이었으며 50$0^{\circ}C$에서 증착한 후 80$0^{\circ}C$의 산소 분위기 하에서 1시간 동안 열처리하였다. 증착시 증착 압력을 변화시켜 가면서 이에 따른 특성의 변화를 고찰하였다. 박막내의 Bi와 Sr의 부족을 보상하기 위해 20mole%의 Bi $O_{2}$와 30mole%의 SrC $O_{3}$를 과잉으로 넣어 타겟을 제조후 사용하였고 박막들의 두께는 300nm의 두께를 가지며 증착압력에 따라 다른 미세 구조르 보였다. 10mtorr에서 증착한 박막의 조성은 S $r_{0.6}$B $i_{3.8}$Ta/ sub 2.0/ $O_{9.0}$이었다. 이 SBT 박막의 잔류 분극(2 $P_{r}$)과 보전계(2 $E_{c}$)값은 각각 인가 전압 5V에서 18.5 $\mu%C/$\textrm{cm}^2$과 150kV/cm이었고, signal/noise비는 3V에서 4.6을 나타내었다. 5V의 bipolar pulse하에서 $10^{10}$cycle까지 피로 현상이 나타나지 않았으며, 누설 전류 밀도는 133kV/cm에서 약 1x$10^{-7A}$$\textrm{cm}^2$의 값을 보였다.을 보였다.

• Korean Journal of Materials Research
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• v.22 no.12
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• pp.696-700
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• 2012

(Na, K) $NbO_3$ thick film was successfully achieved using a sol-gel coating process with the addition of polyvinylpyrrolidone (PVP) to a metal alkoxide solution. The transparent coating solution, mixed with Nb:PVP = 1:1 in a molar ration, was synthesized by evaporating the solvent to over 62.5 wt%. Additive PVP increased the viscosity of the solution so that the coating thickness could be enhanced. The thickness of the (Na, K) $NbO_3$ film assisted by PVP was ca. 320 nm at the time of deposition; this value is four times thicker than that of the sample fabricated without PVP. Also, due to PVP binding with the OH groups of the metal alkoxide, the condensation reaction in the film was suppressed. The crystalline size of the (Na, K) $NbO_3$ films assisted by PVP was ca. 15 nm smaller than that of the film fabricated without PVP. After the sintering process at $700^{\circ}C$, the (Na, K) $NbO_3$ films were mainly composed of randomly oriented (Na, K) $NbO_3$ phase of perovskite crystal structure, including a somewhat secondary phase of $K_2Nb_4O_{11}$. However, by adding PVP, the content of the secondary phase became quite smaller than that of the sample without PVP. It was thought that the addition of PVP might have the effect of restraining the loss of potassium and that PVP could hold metalloxane by strong hydrogen bonding before complete decomposition. Therefore, the film thickness of the (Na, K) $NbO_3$ films could be considerably advanced and made more crack-free by the addition of PVP.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.360-363
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• 2000

Deformation in the hysteresis loop of $Pb(Zr,Ti)O_3$ (PZT) thin films with various Zr/Ti ratios has been studied by varying the top electrode preparation method and the annealing temperature. Pt/PZT/Pt capacitors was found to be positively poled due to dc plasma potential generated during reactive ion etch (RIE) of Rt. Internal field is formed by space charges trapped at domain boundaries. Aging phenomenon such as constriction in the middle of the hysteresis loop was observed in the PZT film with top electrode deposited by sputtering. Top electrode annealing restores the hysteresis loop by removing the space charges. As Zr/Ti ratio decrease, voltage shift increases and an-nealing temperature at which internal field disappears also increases.