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Abstract: Bi3.25Eu0.75Ti3O12 (BET) thin films were deposited on the LaNiO3 (LNO (100))/Si and Pt/Ti/SiO2/Si substrates by the metal-organic decomposition method. Structural and dielectric properties of BET thin films for the applications in nonvolatile ferroelectric random access memories were investigated. Both the microstructure and morphology of the films were analyzed by X-ray diffraction and atomic force microscope. Even at low temperature 650 °C, the BET thin films were deposited on LNO bottom electrode and exhibited [001] orientation. Compared with the films deposited on Pt electrode, the BET thin films on the LNO electrode annealed at 650 °C showed larger dielectric constants and remanent polarization. For the BET thin films on the LNO electrode annealed at 650 °C, the remanent polarization 2P r and coercive field were 45.6 μC/cm2 and 171 kV/cm, respectively. [Copyright &y& Elsevier]

Abstract: Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films were prepared using the spin-coating method onto Pt/Ti/SiO2/Si substrate by the metal organic decomposition. Crystallographic properties of BLT films were characterized as a function of annealing temperature. The effect of excess Bi content on the microstructure and ferroelectric properties was also investigated. X-ray diffraction (XRD) results show that predominant Bi4Ti3O12 phase can be obtained at 550 °C, while the films keep randomly oriented structure up to 750 °C. An increase in grain size of BLT films with increasing annealing temperature was observed by the field emission scanning electron microscopy (FE-SEM). The hysteresis loops of BLT films were found to be well defined for temperatures above 600 °C. The remanent polarization decreased when more than 10% of excess Bi has been used in the precursor solution. The films with both Bi deficiency and Bi excess over 10% in the BLT precursor solution annealed at 650 °C showed poor fatigue properties. This was attributed to the structure defects and to the presence of a secondary phase. The films prepared with the Bi content in excess of 10% and annealed at 650 °C exhibited an outstanding hysteresis behaviors with the remanent polarization (2P r) of 25.66 as well as fatigue-free behavior up to 3.5×109 bipolar cycles. [Copyright &y& Elsevier]

Abstract: BST thin films were etched with inductively coupled plasmas. A chemically assisted physical etch of BST was experimentally confirmed by ICP under various gas mixtures. After a 20% addition of BCl3 to the Cl2/Ar mixture, resulting in an increased the chemical effect. As increases of RF power and substrate power, and decrease of working pressure, the ion energy flux and chlorine atoms density increased. The maximum etch rate of the BST thin films was 90.1 nm/min, and at the RF power, substrate power, and working pressure were 700 W, 300 W, and 1.6 Pa, respectively. It was proposed that sputter etching is dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products. [Copyright &y& Elsevier]

Ba0.6Sr0.4TiO3 (BST) dielectric thin films doped by Cr were prepared using an alkoxide-based sol–gel method on the Pt/Ti/SiO2/Si substrate. Atomic force microscopy and X-ray diffraction analysis showed that increasing the Cr-doping ratio causes increased grain size while the surface remains smooth and crack-free. It was also found that compared with undoped films the increase of Cr content in BST improves the dielectric constant and the leakage-current characteristics. The figure of merit reached the maximum value of 72.3 at the 5 mol% of Cr doping. This composition showed the dielectric constant of 426, the loss factor of 0.0065, tenability of 47.7%, and leakage-current density (at the electric field of 100 kV/cm) of 5.31×10-8 A/cm2. The results show that the Cr-doped BST thin films are prospective candidates for applications in tunable devices. [Copyright &y& Elsevier]

BST thin films were etched with inductively coupled CF4/(Cl2+Ar) plasmas. The maximum etch rate of the BST thin films was 53.6 nm/min for a 10% CF4 to the Cl2/Ar gas mixture at RF power of 700 W, DC bias of -150 V, and chamber pressure of 2 Pa. Small addition of CF4 to the Cl2/Ar mixture increased chemical effect. Consequently, the increased chemical effect caused the increase in the etch rate of the BST thin films. To clarify the etching mechanism, the surface reaction of the BST thin films was investigated by X-ray photoelectron spectroscopy. [Copyright &y& Elsevier]

Etching characteristics of (Pb,Sr)TiO3 (PST) thin films were investigated using inductively coupled chlorine-based plasma system as functions of gas-mixing ratio, radio frequency power and direct current bias voltage. It was found that increasing of Ar content in gas mixture lead to sufficient increasing of etch rate and selectivity of PST to Pt. The maximum etch rate of PST film is 56.2 nm/min and the selectivity of PST film to Pt is 0.8 at Cl2/(Cl2+Ar) of 20%. It was proposed that sputter etching is the dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products. [Copyright &y& Elsevier]

Pb0.5,Sr0.5TiO3 (PST) thin films were deposited on the LaNiO3 (LNO(1 0 0))/Si and Pt/Ti/SiO2/Si substrates by the alkoxide-based sol–gel method. Structural and dielectric properties of PST thin films for the tunable microwave device applications were investigated. The PST films, which were directly grown on the Pt/Ti/SiO2/Si substrates, showed the random orientation. For the LNO/Si substrates, the PST thin films exhibited highly (1 0 0) orientation. Compared with randomly oriented films, the highly (1 0 0)-oriented PST thin films showed better dielectric constant, tunability and figure of merit (FOM). The dielectric constant, tunability and FOM of the highly (1 0 0)-oriented PST thin film increased with increasing annealing temperature due to the decrease in lattice distortion. The differences in dielectric properties may be attributed to the change in the film stress and the in-plane oriented polar axis depending on the substrate that was used. The dielectric constants, dielectric loss and tunability of the PST thin films deposited on the LNO/Si substrates measured at 1 MHz were 483, 0.002 and 60.1%, respectively. [Copyright &y& Elsevier]

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films with Bi4Ti3O12 (BTO) seeding layers were deposited onto a Pt/Ti/SiO2/Si substrate using a metalorganic decomposition method. The effects of variation in the thickness on the microstructural and ferroelectric characteristics were investigated. The BLT thin films with 5-nm-thick BTO seeding layers with a Pt bottom electrode showed that the presence of BTO seeding layer induced a significant change in the crystallinity. This results in an improvement of the (1 1 7) orientation compared with BLT thin films without the BTO seeding layer. The 5-nm-thick BTO seeding layer in the BLT/BTO/Pt/Ti/SiO2/Si structure also prevents the diffusion of Bi into the Pt bottom electrode. The BLT thin films with 5-nm-thick BTO seeding layers showed larger remanent polarization and better fatigue properties compared with the films without the seeding layer. The remanent polarization (2Pr) of BLT thin films without seeding layer and with 5-nm-thick BTO seeding layer annealed at 650 °C were 20.6 and 30 μC/cm2, respectively. [Copyright &y& Elsevier]

The etching behavior of Bi4−xLaxTi3O12 (BLT) films in inductively coupled Ar/Cl2 plasma was investigated in terms of etch parameters. The etching rate as a function of Ar/Cl2 mixing ratio showed a maximum of 50.3 nm/min for the mixture of Ar(80%)/Cl2(20%). The increase of r.f. power and d.c.-bias voltage caused an increase in BLT etch rate under any fixed gas composition. To understand etch mechanism, the plasma diagnostics were performed using Langmuir probe (LP) and optical emission spectroscopy (OES). The LP measurement indicated that the increase of Ar mixing ratio in Ar/Cl2 plasma leads to monotonic changes of both electron density and total density of positive ions. The same tendencies were found for chlorine atoms and molecules using OES. The chemical states of BLT were studied using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that the La-chlorides remained on the etched surface. The analysis of surface reactions and plasma diagnostics in the frameworks of an ion-assisted etching mechanism confirms the possibility of non-monotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment. [Copyright &y& Elsevier]

The metal-ferroelectric-insulator-semiconductor (MFIS) capacitors were fabricated using a metal organic decomposition (MOD) method. The CeO2 thin films were deposited as a buffer layer on Si substrate and Bi3.25La0.75Ti3O12 (BLT) thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated by varying the CeO2 layer thickness. The width of the memory window in the capacitance–voltage (C–V) curves for the MFIS structure decreased with increasing thickness of the CeO2 layer. Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) show no interdiffusion by using the CeO2 film as buffer layer between the BLT film and Si substrate. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory field-effect-transistors (FETs) with large memory window. [Copyright &y& Elsevier]

The etch properties of Bi4−xEuxTi3O12 (BET) thin films were evaluated with inductively coupled CF4/Ar plasma. We obtained the maximum etch rate of 78 nm/min at the gas mixing ratio of CF4 (10%)/Ar (90%). This result may suggest that sputtering by Ar ions is more effective than chemical etching by fluorine atoms for Bi4−xEuxTi3O12 (BET) etching. In X-ray photoelectron spectroscopy analysis, non-volatile etch byproducts (EuF2: 1380 °C, EuF3: 1276 °C) were observed. After the etching, the electrical properties of BET capacitors were characterized in terms of hysteresis curves, leakage current and switching polarization. After etching in CF4/Ar plasma, the remanent polarization decreased and the leakage current increased. The etched capacitors in the Ar/CF4 plasma retained 58% of their original polarization at 105 cycles. After the annealing at 600 °C in an O2 atmosphere for 10 min, the ferroelectric properties were significantly recovered. The degradation of electrical properties after the etching was considered due to the physical effect of ion bombardment and chemical residue contamination. [Copyright &y& Elsevier]

Abstract: The etching characteristics of LaNiO3 (LNO) thin films and SiO2 in Cl2/Ar plasma were investigated. LNO etch rates decreased with increasing Cl2 fraction in Ar plasma and the working pressure. Langmuir probe measurement showed a noticeable influence of Cl2/Ar mixing ratio on electron temperature, electron density, and ion current density. The modeling of volume kinetics for charged particles and OES measurements for neutral atoms indicated monotonous changes of both densities and fluxes of active species such as chlorine atoms and positive ions. The LNO etch rate behavior may be explained by physical mechanisms. [Copyright &y& Elsevier]

Abstract: The metal–ferroelectric–semiconductor (MFS) structure is widely studied for nondestructive readout (NDRO) memory devices, but conventional MFS structure has two critical problems. First, the one that is difficult to obtain ferroelectric films like PZT on Si substrate without interdiffusion of impurities such as Pb, Ti and other elements. Diffusion of Pb or Ti induces increased trap density and Fermi-level pinning. The other one is that PZT/Si structure generates nonferroelectric and low-dielectric constant layer at the interface. In order to solve these problems, the metal–ferroelectric–insulator–semiconductor (MFIS) structure has been proposed with a buffer layer of high dielectric constant such as MgO, Y2O3, and CeO2. Buffer layer candidate should meet the following requirements of low lattice mismatch, low leakage current, low interface-state density, high dielectric constant, chemical stability, and prevention of interdiffusion. In this study, the etching characteristics (etch rate, selectivity) of MgO thin films were etched using Cl2/Ar plasma. The maximum etch rate of 85 nm/min for MgO thin films was obtained at Cl2(30%)/Ar(70%) gas mixing ratio. Moreover, the etch rate was measured by varying the etching parameters such as ICP rf power, dc-bias voltage, and chamber pressure. Plasma diagnostics was performed by Langmuir probe (LP) and optical emission spectroscopy (OES). [Copyright &y& Elsevier]

In this work, to investigate improvement of the damage using oxygen containing plasma, we etched PZT films as a function of Ar (x%)/O2 (y%) gas mixing ratio in Cl2 (56%)/CF4 (14%) plasma (where the sum of x and y is 30). The maximum etch rate of the PZT thin films was 146 nm/min for Ar (30%)/O2 (0%) added into the Cl2/CF4 plasma. After the etching, the plasma-induced damages were characterized in terms of hysteresis curves, leakage current, switching polarization and retention capacity as a function of the gas mixing ratio. When the ferroelectric properties of PZT films were etched as a function of O2 and Ar and the gas mixing ratios were compared, the value of remnant polarization in O2 (30%) added Cl2/CF4 plasma is higher than that in Ar (30%). The results showed that after the etching the charges accumulated by oxygen vacancies prevented further domain switching at the top electrode–ferroelectric interface and created leakage current because of modification of the interfacial Schottky barrier during the etching process. The physical damage to the near surface and the crystal structure of the etched PZT thin films was evaluated by using X-ray diffraction (XRD). The remnant polarization, leakage current, retention and fatigue properties are improved with increasing O2 content. From XRD results, the improvement in the ferroelectric properties of PZT capacitors etched in O2 containing plasma was consistent with the increased intensities of the (100) and (200) peaks. [Copyright &y& Elsevier]