• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2003.12a
• /
• pp.78-81
• /
• 2003

• Korean Journal of Materials Research
• /
• v.13 no.12
• /
• pp.846-849
• /
• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05c
• /
• pp.49-52
• /
• 2003

The role of gas ratio with the crystallization behavior and electrical properties in $Bi_{3.25}La_{0.75}Ti_3O_{12}$(BLT) thin films by rf magnetron sputtering method has not been precisely defined. In this work, the ferroelectric properties of these films with gas variation was investigated. BLT thin films were deposited on the Pt/Ti bottom electrode by rf magnetron sputtering method and then they were crystallized by rapid thermal annealing (RTA). The experiment showed that all BLT films indicated perovskite polycrystalline structure with preferred orientation (020) and (0012). And no pyrochlore phase was observed. The fabricated film annealed with $O_2$ of 15 sccm showed that value of leakage current was $9.67{\times}10^{-7}A/cm^2$ at 50kV /em, and the value of remanent polarization (2Pr=Pr+-Pr-) was $11.8{\mu}C/cm^2$. Therefore we induce access to memory device application by rf-magnetron sputtering method in this report.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.7
• /
• pp.575-580
• /
• 2007

A 16 Mb 1T1C FeRAM device was integrated with BLT capacitors. But a lot of cells were failed randomly during the measuring the bit-line signal distribution of each cell. The reason was revealed that the grain size and orientation of the BLT thin film were severely non-uniform. And the grain size and orientation were severely affected by the process conditions of post heat treatment, especially nucleation step. The optimized annealing temperature at the nucleation step was $560^{\circ}C$. The microstructure of the BLT thin film was also varied by the annealing time at the step. The longer process time showed the finer grain size. Therefore, the uniformity of the grain size and orientation could be improved by changing the process conditions of the nucleation step. The FeRAM device without random bit-fail cell was successfully fabricated with the optimized BLT capacitor and the sensing margin in bit-line signal distribution of it was about 340 mV.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2002.11a
• /
• pp.69-71
• /
• 2002

$(Bi, La)Ti_{3}O_{12}(BLT)$ ferroelectric thin films were prepared on $Al_{2}O_{3}/Si$ substrates by the sol-gel method. The as-coated films were post-annealed at the temperature of $650^{\circ}C$ and $700^{\circ}C$ for 30 min. The crystallinty, surface morphologies and electrical properties were affected by the annealing temperatures. The BLT films annealed at above $650^{\circ}C$ exhibited typical bismuth layered perovskite structures with (00$\ell$) preferred orientation. The granular shaped grains with a size of approximately 90nm was formed in the film sample annealed at $700^{\circ}C$. The memory window volatge of the BLT film was 2.5V. The leakage current of BLT films annealed at $650^{\circ}C$ was about $1\times10^{-7}A/\textrm{cm}^2$ at 3V.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.533-534
• /
• 2006

1mm-thick BLT ceramics were sintered in accordance with a bulk ceramic fabrication process. All XRD peaks detected in the sintered ceramics were indexed as the Bi-layered perovskite structure without secondary phases. Density was increased with increasing the sintering temperature up to $1050\;^{\circ}C$ and the maximum value was about 98% of the theoretical density. The remanent polarization (2Pr) value of BLT ceramic sintered at $1050\;^{\circ}C$ was approximately $6.5\;{\mu}C/cm^2$ at the applied voltage of 4.5kV. From these results, a BLT ceramic target for plused laser deposition (PLD) system was successfully fabricated.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2004.02a
• /
• pp.65-65
• /
• 2004

• 한국전자현미경학회:학술대회논문집
• /
• 2003.11a
• /
• pp.49-51
• /
• 2003

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.1 s.34
• /
• pp.21-26
• /
• 2005

The field effect transistors (FETs) were fabricated ell $Y_2O_3/Si(100)$ substrates by the conventional memory processes and sol-gel process using $(Bi,La)Ti_3O_{12}(BLT)$ ferroelectric gate materials. The remnant polarization ($2Pr = Pr^+-Pr^-$) int Pt/BLT/Pt/Si capacitors increased from $22 {\mu}C/cm^2$ to $30{\mu}C/ cm^2$ at 5V as the annealing temperature increased from $700^{\circ}C$ to $750^{\circ}C$. There was no drastic degradation in the polarization values after applying the retention read pulse for $10^{5.5}$ seconds. The capacitance-voltage data of $Pt/BLT/Y_2O_3/Si$ capacitors at 5V input voltage showed that the memory window voltage decreased from 1.4V to 0.6V as the annealing temperature increased from $700^{\circ}C$ to $750^{\circ}C$. The leakage current of the $Pt/BLT/Y_2O_3/Si$ capacitors annealed at $750^{\circ}C$ was about $510^{-8}A/cm^2$ at 5V. From the drain currents versus gate voltages ($V_G$) for $Pt/BLT/Y_2O_3/Si(100)$ FET devices, the memory window voltages increased from 0.3V to 0.8V with increasing tile $V_G$ from 3V to 5V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.3
• /
• pp.223-227
• /
• 2007

The effect of Eu contents on the ferroelectric properties of $Bi_{4-x}Eu_xTi_3 O_{12}$ (BET) thin films has been investigated. Bismuth Europium titanate thin films with a Eu contents were prepared on the $Pt/Ti/SiO_2/Si$ substrate by metal-organic decomposition technique. The structure and the morphology of the films were analyzed using X-ray diffraction (XRD) and field emission scanning microscopy (FE-SEM), respectively. From the XRD analysis, it was found that BET thin films have polycrystalline structure, and the layered-perovskite phase is obtained when the Eu contents exceeds 0.2 (x > 0.2). Also, the ferroelectric characteristics of the BET thin films were found to be dependent on the Eu content. Particularly, the BET films doped with x = 0.75 show better ferroelectric properties (remanent polarization 2Pr = 60.99 C/$cm^2$ and only a little polarization fatigue up to $3.5{\times}10^9$ bipolar switching cycling) than those doped with other Eu contents.