Papers by Keyword: FeRAM

Abstract: The properties and applications of materials with non-volatile memory based on HfO₂ were briefly considered. In addition, an overview of the obtained results was given. On the basis of these results, the possibility of use of the structures TiN/ Hf_0.5Zr_0.5O₂/ TiN/ SiO₂/ Si and TiN/ HfxAl_1-xO_y/ Pt/ SiO₂/ Si for the non-volatile memory of FeRAM and ReRAM types obtained by the atomic-layer deposition was shown. In addition, the scalability of these elements and opportunity to create promising submicron integrated circuits for ferroelectric and resistive memory were demonstrated.

Abstract: The term "Multiferroic" is coined for a material possessing at least two ferroic orders in the same or composite phase (ferromagnetic, ferroelectric, ferroelastic); if the first two ferroic orders are linearly coupled together it is known as a magnetoelectric (ME) multiferroic. Two kinds of ME multiferroic memory devices are under extensive research based on the philosophy of "switching of polarization by magnetic fields and magnetization by electric fields." Successful switching of ferroic orders will provide an extra degree of freedom to create more logic states. The "switching of polarization by magnetic fields" is useful for magnetic field sensors and for memory elements if, for example, polarization switching is via a very small magnetic field from a coil underneath an integrated circuit. The electric control of magnetization is suitable for nondestructive low-power, high-density magnetically read and electrically written memory elements. If the system possesses additional features, such as propagating magnon (spin wave) excitations at room temperature, additional functional applications may be possible. Magnon-based logic (magnonic) systems have been initiated by various scientists, and prototype devices show potential for future complementary metal oxide semiconductor (CMOS) technology. Discovery of high polarization, magnetization, piezoelectric, spin waves (magnon), magneto-electric, photovoltaic, exchange bias coupling, etc. make bismuth ferrite, BiFeO₃, one of the widely investigated materials in this decade. Basic multiferroic features of well known room temperature single phase BiFeO₃ in bulk and thin films have been discussed. Functional magnetoelectric (ME) properties of some lead-based solid solution perovskite multiferroics are presented and these systems also have a bright future. The prospects and the limitations of the ME-based random access memory (MERAM) are explained in the context of recent discoveries and state of the art research.

Abstract: Perovskite Ba(Zr0.1Ti0.9)O3 (BZ1T9) ferroelectric thin films well deposited on ITO/glass substrates for applications in system-on-panel (SOP) devices are produced and investigated. The sputtering parameters of as-deposited BZ1T9 thin films were rf power of 160 W, chamber pressure of 10 mTorr, substrate temperature of 550oC, and an oxygen concentration of 40%. From the SEM cross- sectional observation, the deposition rate were about 2.5 nm/min. Additionally, the maximum dielectric constant and leakage current density of annealed BZT films under the rapid temperature annealing would be increased, as the temperature increased to 6500C. Further, the maximum remnant polarization and coercive field of BZT films were found and calculated from the p-E curves.

Abstract: A 16Mb 1T1C FeRAM device was successfully fabricated with the lead-free BLT capacitors. The average value of the switchable polarization obtained in the 32k-array (unit capacitor size: 0.68 μm2) BLT capacitors was about 16 μC/cm2 at the applied voltage of 3V and the uniformity within an 8-inch wafer was about 2.8%. But random bit failures were detected during the measuring the bit-line signal of each cell. It was revealed that the grain size and orientation of the BLT thin film were severely non-uniform. Therefore, the grain size and orientation was optimized by varying the process conditions of nucleation step. The random bit failure issue was solved by adopting the optimized BLT film. The cell signal margin of the optimized FeRAM device was about 340 mV.

Abstract: A 16Mb 1-transistor /1-capacitor (1T1C) FeRAM device was fabricated with lead-free Bi3.25La0.75Ti3.0O12 (BLT) capacitors. The key integration processes contain a scalable MTP (Merged Top-electrode and Plate-line) cell structure and reliable BLT ferroelectric capacitors. Ferroelectric properties of BLT films were optimized on the newly developed MTP cell structure. BLT films were coated on Pt/IrOx/Ir bottom electrode using sol-gel solutions. The composition of the optimized BLT film was about Bi3.25La0.75Ti3.0O12. The switchable polarization obtained in a 100nm-thick BLT film was about 20 µC/cm2 at the 3 V applied voltage, and the optimized BLT film showed a few fatigue losses about 10% up to 1 × 1011 cycles. The imprint properties of the BLT film were also characterized at 25°C and 90°C operating temperature after 125°C data storage. The average cell signal sensing margin between data "1" and data "0" was measured to be about 900 mV, which is a sufficiently large margin for device operation.

Abstract: Ferroelectric properties of Pb-free (Bi,La)4Ti3O12 (BLT) films were optimized on a newly developed MTP cell structure. BLT films were coated on Pt/IrOx/Ir bottom electrode using sol-gel solutions. The composition of the optimized BLT film was about Bi3.25La0.75Ti3.0O12, which was analyzed by ICP-MS method. The switchable polarization obtained in a 100nm-thick BLT film was about 20 uC/cm2 at the 3 V applied voltage, and the optimized BLT film showed little fatigue loss about 10% up to 1×1011 cycles. The imprint properties of the BLT film were also characterized at 25 °C and 90 °C operating temperature after 125 °C data storage. Regardless of operating temperature, switchable polarization of BLT had a sufficiently large margin for device operation up to 10 years.