• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.66-74
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• 2000

The structural and electrical characteristics of SBT thin films, fabricated on Pt/Ti/SiO\ulcorner/Si substrates by a pulsed laser deposition(PLD), were investigated to develop ferroelectric thin films for capacitor lay-ers of FRAM. EFfects of target composition on the characteristics of SBT thin films were examined. Target were prepared by mixed oxide method, and composition of Sr/Bi/Ta on SBT was changed to 1/2/2, 1/2.4/2, 1/2.8/2, 0.8/2/2 and 1.2/2/2. SBt thin films were fabricated, as a function of substrate temperature and oxygen pressure, by PLD. The optimized ocndition, to fabricate high quality SBT thin films, was 700 $^{\circ}C$ of substrate temperature, 200 mTorr of oxygen pressure, and 2 J/$\textrm{cm}^2$ of laser energy density. Maximum remnant value(2Pr) of 9.0 $\mu$C/$\textrm{cm}^2$, coercive field value(Ec) of 50 kV/cm, dielectric constant value of 166, and leakage current densities of <10\ulcorner A/$\textrm{cm}^2$ were observed for the films with 1/2/2 composition, which was prepared at the above PLD condition.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권3호
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• pp.128-132
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• 2004

The perovskite ferroelectric materials of the PZT, SBT and BST series will attract much attention for application to ULSI devices. Among these materials, the BST ($Ba_0.6$$Sr_0.4$/$TiO_3$) is widely considered the most promising for use as an insulator in the capacitors of DRAMS beyond 1 Gbit and high density FRAMS. Especially, BST thin films have a good thermal-chemical stability, insulating effect and variety of Phases. However, BST thin films have problems of the aging effect and mismatch between the BST thin film and electrode. Also, due to the high defect density and surface roughness at grain boundarys and in the grains, which degrades the device performances. In order to overcome these weakness, we first applied the chemical mechanical polishing (CMP) process to the polishing of ferroelectric film in order to obtain a good planarity of electrode/ferroelectric film interface. BST ferroelectric film was fabricated by the sol-gel method. And then, we compared the surface characteristics before and after CMP process of BST films. We expect that our results will be useful promise of global planarization for FRAM application in the near future.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1881-1883
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• 2005

In this study, PZT thin films were fabricated using sol-gel Processing onto $Si/SiO_2/Ti/Pt$ substrates. PZT sol with different Zr/Ti ratio(20/80, 30/70, 40/60, 52/48) were prepared, respectively. The films were fabricated by using the spin-coating method on substrates. The films were heat treated at $450^{\circ}C$, $650^{\circ}C$ by rapid thermal annealing(RTA). The preferred orientation of the PZT thin films were observed by X-ray diffraction(XRD), and Scanning electron microscopy(SEM). All of the resulting PZT thin films were crystallized with perovskite phase. The fine crystallinity of the films were fabricated. Also, we found that the ferroelectric properties from the dielectric constant of the PZT thin films were over 600 degrees, P-E hysteresis constant. And the leakage current densities of films were lower than $10^{-8}\;A/cm^2$. It is concluded that the PZT thin films by sol-gel process to be convinced of application for ferroelectric memory device.

• 전기학회논문지P
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• 제63권1호
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• pp.46-49
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• 2014

$Pb(Zr_{0.52}Ti_{0.48})O_3(PZT)$ thin films deposited on $Ru/RuO_2$ bottom electrode that grown for in-situ progress used rf magnetron sputtering method. We investigated the dependence of the crystalline and electrical properties in the way of capacitors PZT thin films. Our results show that all PZT films indicated polycrystalline perovskite structure with preferred orientation (110) and no pyrochlore phase is observed. The electric properties of the Ru improved with increasing Ru thin films thickness. A well-fabricated Ru/PZT/Ru (100 nm) /$RuO_2$ capacitor showed a leakage current density in the order of $2.03{\times}10^{-7}$ $A/cm^2$ as a 50 kV/cm, a remnant polarization (Pr) of 9.22 ${\mu}C/cm^2$, and a coercive field (-EC) of -32.22 kV/cm. The results show that $Ru/Ru/RuO_2$ bottom electrodes are expected to reduce the degradation ferroelectric fatigue and excellent ferroelectric properties.

• Transactions on Electrical and Electronic Materials
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• 제5권6호
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• pp.223-226
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• 2004

The PZT thin films are one of well-known materials that has been widely studied for ferroelectric random access memory (FRAM). We etched the PZT thin films by $CF_{4}/(Cl_{2}+Ar)$ plasma and investigated improvement in etching damage by $O_{2}$ annealing. The maximum etch rate of the PZT thin films was 157 nrn/min and that the selectivity of the PZT thin films to Pt was 3.1 when $CF_{4}(30{\%})$ was added to a $Cl_{2}(80{\%})/Ar(20{\%})$ gas mixing ratio. To improve the ferroelectric properties of PZT thin films after etching, the samples were annealed for 10 min at various temperatures in $O_{2}$ atmosphere. After $O_{2}$ annealing, the remanent polarization of the asdeposited films was $34.6{\mu}/cm^{2}$ and the sample annealed at 650, 550, and $450^{\circ}C$ was 32.8, 22.3, and $18.6{\mu}/cm^{2}$, respectively. PZT thin films with $O_{2}$ annealing at $450^{\circ}C$ retained $77{\%}$ of their original polarization at 106 cycles. Also as the annealing temperature increased, the fatigue properties improved. And the leakage current was decreased gradually and almost recovered to the as-deposited value after the annealing at $450^{\circ}C$.

• 한국세라믹학회지
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• 제35권9호
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• pp.945-952
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• 1998

Ferroelectric Sr0.8Bi2.4Ta2O9 stock solutions were prepared by MOD(Metaloganic Decompostion) process. The phase transformation for the layered perovskite of the SBT thin films by changing RTA(Rapid her-mal Annealing) temperatuer from 700$^{\circ}C$to 780$^{\circ}C$ were observed using XRD and SEM. Layered perovskite phase began to appear above 740$^{\circ}C$ and then SBT thin films were annealed at 800$^{\circ}C$ for 1hr for its com-plete crystallization. The specimens showed well shaped hysteresis curves without post annealing that car-ried out after deposition of Pt top electrode. The SBT thin films showed the asymmetric ferroelectric pro-perties. It was confirmed that the properties were caused by interface effect to SBT and electrode by leak-age current density measurement and asymmetric properties reduced by post annealing. At post annealing temperature of 800$^{\circ}C$ remanant polarization values (2Pr) were 6.7 9 ${\mu}$C/cm2 and those of leakage current densities were 3.73${\times}$10-7 1.32${\times}$10-6 A/cm2 at 3, 5V respectively. Also bismuth bonding types of SBT thin film surface were observed by XPS.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.341-342
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• 2006

Gadolinium-substituted bismuth titanate, $Bi_{3.3}Gd_{0.7}Ti_3O_{12}$ (BGT), thin films were successfully fabricated on Pt(111)/Ti/$SiO_2$/Si substrates by a sol-gel method and their structural and ferroelectric properties have been characterized. Fabricated BGT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The remanent polarization ($2P_r$)) of BGT thin film annealed at $720^{\circ}C$ was $25.85\;{\mu}C/cm^2$ at an applied voltage of 5 V. The BGT thin films exhibited a 11 % reduction in their switching charge after no less than $10^{11}$ switching cycles at a frequency of 1 MHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.366-367
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• 2006

Different orientated SBN thin films were deposited by Ion Beam Sputtering, and electric properties were measured on each orientation. Ferroelectric $Sr_xBa_{1-x}Nb_2O_6$(SBN) has excellent electro-optic, photo-refractive, piezoelectric, pyroelectric properties. SBN thin film has been deposited by various method, of sol-gel, PLD, CVD, sputtering, etc.. To avoid lead pollution of Pb-system perovskite ferroelectric materials. SBN thin films were fabricated for pyroelectric IR sensor. Using the ceramic target of the same composition and Pt(100)/$TiO_2/SiO-2$/Si(100) substrate, crystallization and orientation behavior as well as electric properties of the films were examined. Seed layer and thin films thickness was controlled to observe the effect on preferred orientation. We measured I-V, C-V, P-E hysteresis to characterize electric-properties on each orientations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.51-54
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• 2003

Tb-doped lead zirconate titanate($Pb_{1.1}(Zr_{0.6}Ti_{0.4})O_3$; PZT) thin films on $Pt(111)/Ti/SiO_2/Si(100)$ substrates prepared by a sol-gel method. Films have a Zr/Ti ratio of 60:40 and perovskite phase structure. The effect on the structural and electrical properties of films measured according to Tb content. Dielectric and ferroelectric properties of PZT thin films were altered significantly by Tb-doping. The PZT thin film with higher dielectric constant and improved leakage current characteristic was obtained by adding 0.3 mol% Tb. At 100 kHz, the dielectric constant and the dielectric loss of the 0.3 mol% Tb-doped PZT thin film were 1611 and 0.24, respectively The remanent polarization(2Pr) of the 0.3 mol% Tb-doped PZT thin film was $61.4\;{\mu}C/cm^2$ and the coercive field was 61.9 kV/cm. Tb-doped PZT thin films showed improved fatigue characteristics comparing to the undoped PZT thin film.