Influence of Post-Annealing on the Characteristics of Pb(Zr,Ti)O3 Thin Films Deposited by Liquid Delivery MOCVD Using a Cocktail Solution

Ferroelectric PZT thin films were deposited by liquid delivery MOCVD using a cocktail solution. The cocktail solution consisted of Pb(METHD)₂, Zr(METHD)₄ and Ti(MPD)(METHD)₂ diluted with ethylcyclohexane. The films deposited on Pt/Ti/SiO₂/Si at a substrate temperature of 500°C consisted of PZT, PbO and PbPt_x, and showed poor properties. However, after annealing at 450°C in air for thirty minutes, the PbPt_x phase disappeared while the volume of the PbO phase increased. The hysteresis properties were also improved by annealing at 450°C. After annealing at 600°C in air for thirty minutes, the PbPt_x and the PbO phases disappeared perfectly and the PZT thin films showed good hysteresis properties with the remanent polarization of 30 μC/cm² and the coercive field of 88 kV/cm.     

Characterization of Pb(Zr,Ti)O3 thin films on SOI prepared by excimer laser deposition

Abstract

Ferroelectric Pb(Zr,Ti)O₃ (PZT) thin films were prepared by pulsed excimer laser deposition on Silicon-on-Insulator (SOI) substrates with and without an electrode. Their properties can be improved by rapid thermal annealing, based on the structural and interfacial characteristics analysis by X-ray diffraction, Rutherford backscattering spectroscopy and automatic spreading resistance measurements. The thin films were revealed of to be polycrystalline perovskite structure with mainly ?100? and ?110? orientations; the crystallite size and the structure are dependent on the annealing time. The PZT thin films did not interact with the top silicon layers of SOI, and the composition was on the tetragonal side of the morphotropic phase boundary in the PbTiO₃-PbZrO₃ phase diagram.     

Preparation of SrBi2Ta2O9 ferroelectric thin film by rf magnetron sputtering

Abstract

SrBi₂Ta₂O₉ (SBT) thin films were deposited on 6-inch Pt/Ti/SiO₂/Si substrates by rf magnetron sputtering using a 12-inch ceramic SBT single target. It is found that several sputtering parameters such as argon (Ar) pressure and rf power were very effective to control the Bi content of SBT thin films which is essential for obtaining good ferroelectric properties.     

Novel diffusion control process using ultra thin buffer layer for MFIS memory

Abstract

MFIS structures having excellent clear interfaces and well-crystallized ferroelectric layer were successfully fabricated by a newly developed ultra thin metal buffer layer process on SiO₂/Si. We examined the effect of sputtered Zr or ZrO₂ ultra thin films as a buffer layer for Pb_xLa_1?xTiO₃ (PLT) growth. TEM observation revealed that the buffer layer formation process in which Zr oxidized after the metal deposition had advantages to produce MFIS structures. This method is also superior for the crystallization and the control of the orientation of PLT thin film on amorphous SiO₂. Especially, for buffer layer thicknesses below 10 nm, preferred c-axis oriented PLT thin films were grown. The I-V characteristics of MFIS-FET fabricated by the proposed method showed a clear memory window due to the remanent polarization of the ferroelectric thin film. This process is the most attractive candidate for realizing MFIS structure memory.     

Processing optimization of solution derived PbZr1−xTixO3 thin films for piezoelectric applications

Abstract

Processing optimization allowed the sol-gel fabrication of 1 μm thick, phase pure perovskite thin films with identical grain size and controlled texture. This made it possible to fabricate stress compensated beams to measure the transverse piezoelectric coefficient over the whole composition range of PbZr_1?xTi_xO₃. The highest value of -12.1 C/m² was measured for (100)/(001) textured PZT53/47. For (111) textured films the maximum value of -8.7 C/m² was found to be in the tetragonal phase field at 55% Ti.     

Structural and Electrical Properties of Ba(ZrxTi1-x)O3 Films Prepared by RF-magnetron Sputtering Using Metal Targets

Ba(Zr_xTi_1-x)O₃ (BZT) thin films with different Zr contents were deposited on (100)MgO and (100)Pt/(100)MgO substrates by RF-magnetron sputtering using metal targets. The BZT thin films had a single perovskite phase with only (001)/(100) orientation. In all cases, the ratio of Ba/Ti was stoichiometry and BZT films possess a dense microstructure. The grain size was decreased and BZT thin films showed ferroelectric-to-paraelectric properties with increasing Zr content. At room temperature, the tunability of nearly 30% was achieved at 1 MHz; meanwhile, a relatively low dielectric loss was obtained. These results indicated that we succeeded in depositing high-quality and potential tunable ferroelectrics.     

Preparation of BaPbO3 Electrode Thin Films by RF Magnetron Sputtering

For electrode materials of Pb(Zr,Ti)O₃ (PZT) thin films in ferroelectric random access memory (FeRAM), various materials have been studied. As new electrode material with which the polarization and fatigue properties are improved, we take notice of barium metaplumbate BaPbO₃ (BPO). Because the BPO contained lead (Pb) and oxygen is conductor that adopted same perovskite structure as PZT. BPO thin films were prepared by rf magnetron sputtering on various substrates. (SiO₂/Si, MgO, Al₂O₃ and Pt-coated substrates), and influence of growth conditions (sputtering gas, rf power, the substrate-heating temperature and post anneals) on crystallization and conductivity were investigated. In case of post anneal after sputtering at room temperature, perovskite single phase was obtained above 400°C. In case of substrate heating while sputtering, without post anneal, perovskite single phase was obtained at 350–500°C on SiO₂/Si substrates (110) preferred orientation BPO films obtained at low temperature, and resistivity of the films decreased at decreasing sputtering temperature. Resistivity of the film at substrate temperature 350°C was 3 × 10^?3 Ω cm. In the case of single crystal substrate, the BPO films were epitaxially grown. Orientation of the films was varied with the sputtering condition. The epitaxial PZT thin films were also grown on the BPO, revealing that PZT(111)[011] //BPO(111)[011] //Pt(100)[011] //MgO(100)[011] and PZT(111)[011] //BPO(111)[011] //Pt(111)[011] //Al₂O₃(001)[100] structures were obtained, and their ferroelectric properties were also evaluated.     

Electrical characteristics of high dielectric constant BCTZ thin films

Abstract

High dielectric constant Ba_0.96Ca_0.04Ti_0.84Zr_0.16O₃ (BCTZ) thin films were deposited on Pt/Ti/SiO₂/Si substrates by spin on metal-organic decomposition (MOD) technique. Undoped and 0.4% Mg-doped BCTZ thin films were annealed in the temperature range from 600 to 900 °C for 1 hour in oxygen environment. The crystal structure of BCTZ thin films was analyzed by X-ray diffraction. The electrical properties of BCTZ thin films were investigated by capacitance—voltage (C—V) characteristics. Also, the electrical properties of these films were compared in conjunction with 0.4% Mg doping effect of BCTZ thin films for possible high dielectric constant material applications.     

Fabrication and Characterization of Ba(Ti,Zr)O3 Thin Films Through the Chemical Solution Deposition Process

Lead- and bismuth-free Ba(Ti_{1 ? x} Zr _x )O₃ (BTZ) thin films were fabricated on Pt(111)/Ti/SiO₂/Si(100) substrates by the chemical solution deposition (CSD) process. The single phase BTZ thin films were obtained at 650°C by conventional process and the control of lattice parameter a was possible by Zr substitution. As the D-E hysteresis loops and J-V characteristics depended on the precipitates on film surface, the fabrication process was reexamined by 2-step sintering process. Consequently the decreasing of first sintering time was able to prevent the precipitates, and the larger grain of about 40–50 nm were obtained by additional sintering for 2 hour.     

Characteristics of Bi4Ti3O12 thin films on ITO/glass and Pt/Si substrates prepared by R.F. sputtering and rapid thermal annealing

Bi₄Ti₃O₁₂ thin films are deposited on ITO/glass and Pt/Ti/Si(100) substrates by R.F. magnetron sputtering at room temperature. The films are then heated by a rapid thermal annealing (RTA) process conducted in oxygen atmosphere at temperatures ranging from 550–700^∘C. X-ray diffraction examination reveals that the crystalinity of the films grown on Pt/Ti/Si is better than that of the films grown on ITO/glass under the same fabrication conditions. SEM observation shows that the films grown on Pt/Ti/Si are denser than those grown on ITO/glass substrates. Interactive diffusion between the Bi₄Ti₃O₁₂ film and the ITO film increases with the increase of annealing temperature. The optical transmittance of the thin film annealed at 650^∘C is found to be almost 100% when the effect of the ITO film is excluded. The relative dielectric constants, leakage currents and polarization characteristics of the two films are compared and discussed.     

Characteristics of Textured Ce-Zr Mixed-Oxide Films as Buffer Layer for YBCO Coated Conductors

Single- and multi-layer (Ce_{1 – x} Zr _x )O₂ films (0 x 0.84) on Si (100) and polycrystalline Ni substrates were prepared using RF and DC magnetron co-sputtering. XRD of scan analysis showed that all (Ce_{1 – x} Zr _x )O₂ films were biaxially oriented with the c-axis perpendicular to the plane of the film. During sputtering, DC power to the Zr target was fixed at 200 W, while RF power to the Ce target was set at 30 W, 50 W, or 100 W. As-deposited ZrO₂ film was amorphous and was crystallized by post-annealing. However, as-deposited (Ce_{1 – x} Zr _x )O₂ films were crystalline even when grown at room temperature and the structures of films were cubic or tetragonal depending on the Ce ion incorporation. It was found that multilayered CeO₂/(Ce_{1 – x} Zr _x )O₂/CeO₂ films could be deposited with a continuous compositional gradient in a sputtering batch. This layered CeO₂/CZO/CeO₂ structure can maintain its original texture after 800°C annealing and is therefore suitable for subsequent YBCO film growth. Furthermore, Ni diffusion is effectively blocked by the buffer layers just like the YSZ currently used in coated conductor fabrication.     

Preparation of Bi4Ti3O12 thin films by electron cyclotron resonance sputtering

Abstract

Ferroelectric Bi₄Ti₃O₁₂ thin films were deposited on Pt-coated oxidized Si substrate by electron cyclotron resonance (ECR) sputtering using ceramic targets. Crystal structure and dielectric properties of the films were investigated as functions of sputtering conditions such as substrate temperature and sputtering gas. Using a target with excess Bi content compared to stoichiometric composition was required to compensate Bi re-evaporation from the substrate and to obtain a perovskite single phase at 600°C. (117)-oriented films exhibited ferroelectric hysteresis loops. The remanent polarization and coercive field of the films were 9.8 μC/cm² and 180 kV/cm, respectively.     

Properties of PbZrxTi1−xO3/CeO2/SiO2/Si structure

Abstract

We report the crystalline quality and electrical properties of PbZr_xTi_1?xO₃ (PZT) films on n-type Si(100) substrates with CeO₂/SiO₂ dual buffer layers. PZT films and CeO₂ buffer layers were prepared by pulsed laser deposition technique, and SiO₂ buffer layers were formed by thermal dry oxidation. It was found that CeO₂/SiO₂ dual buffer layers effectively prevented Si and Pb interdiffusion between PZT and Si substrates. Furthermore, the capacitance-voltage (C-V) characteristics of the PZT/CeO₂/SiO₂/Si heterostructures demonstrated ferroelectric switching properties, showing a memory window as large as 2.7 V at 1 MHz.     

MOCVD PBZRxti1−xo3 thin films on platinized silicon wafers and srtio3 crystals

Abstract

PbZr_xTi_1-xO₃ (PZT) thin films were grown on 6” platinized silicon substrates (Pt / Si) and SrTiO₃ (STO) crystals by Metal-Organic Chemical Vapor Deposition (MOCVD) as a function of the Zr / (Zr+Ti) ratio in the gas phase. Morphology, optical properties, and crystal structure were investigated by scanning electron microscopy, atomic force microscopy, ellipsometry, and X-ray diffraction. The morphology, structure, and optical properties of the polycrystalline and epitaxial films were compared. The determination of the refractive index by ellipsometry (from 550 nm to 2000 nm) was not sensible for the films grown on (Pt / Si) but successful for the films grown on SrTiO₃.     

Composition measurement of paraelectric SrTiO3 layer

Abstract

Since composition is an important parameter affecting the dielectric properties in paraelectric SrTiO₃ layers, composition is determined by Rutherford backscattering spectrometry (RBS) measurement. In this measurement, specifically for achieving precise composition measurement, the RBS spectra of Sr, Ti and O must be separated individually. This spectrum separation can only be attained when thin (800 A[ddot] thick) Sr_xTiO_y layers are deposited on graphite substrate. The measurement is performed for layers deposited at different O₂ partial pressure ratios and sputtering pressures. This measurement indicates that composition of O, y, in Sr_xTiO_y layer decreases from 3.7 to 2.7 with the decrease of O₂ partial pressure raito, R(=O₂/O₂ + Ar) from 1.0 to 0.83. Composition of Sr, x, also changes from 1.1 to 0.6 with this change. With the decrease of sputtering pressure from 10 to 5 mTorr, however, composition, y, is held at 2.7 and only the composition, x, increases from 0.6 to 1.1. This composition measurement is useful for the deposition of optimized dielectric layer employed in the charge storage capacitor.     

The Electrical Conductance of SrFeO2.5+x Thin Films

Thin films of the non-stoichiometric perovskite SrFeO_2.5+x have been grown by the pulsed excimer laser deposition technique onto sapphire substrates. The electrical conductance properties of the thin films have been determined in a series of experiments done both isothermally and with programmed temperature changes from ambient to 490°C and under O₂/N₂ atmospheres with oxygen concentrations in the range from 100 ppm to 100%. Over these ranges of temperature and oxygen partial pressure a wide range of oxygen stoichiometry in SrFeO_2.5+x occurs (approximately 0 < x < 0.5), which includes all four known phases in the SrFeO_{2.5 + x} + O₂ system. The experimentally measured values for the activation energy of conduction, _A, for SrFeO_2.5+x films at temperatures 100 < T < 200°C are in the range 0.30 < _A < 0.47 eV under oxygen at partial pressures 0.001 O ₂)< 0.05 atm and 0.18 < _A < 0.28 eV for 0.2 O ₂)< 1 atm. These values for _A are typical for compositions of SrFeO_2.5+x with stoichiometries in the range 0.25 < x < 0.45. For T < 300°C and for P(_{O 2})< 0.001 atm the films were essentially insulators. For T > 250^°C and P(_{O 2})> 0.001 atm, the oxygen stoichiometries of the films change during the programmed temperature ramps. For these conditions, the values _A/ T exhibit minima/maxima in the temperature range 250 < T < 320^°C which are interpreted as being due to the onset of the order-disorder phase transition from the cubic to the tetragonal and orthorhombic ordered phases of SrFeO_2.5+x with oxygen stoichiometry in the range 0.08 < x < 0.38. The SrFeO_2.5+x thin films have application as oxygen sensing materials, and a relationship between conductance and oxygen sensitivity, S _ox , has been derived. The values of S _ox for SrFeO_2.5+x thin films increases by more than an order of magnitude for compositions close to the lower stoichiometric limit where the principal phase conversion is between the cubic perovskite and the brownmillerite forms.     

Fatigue properties of Sb doped PZT thin films deposited by dc reactive sputtering

Abstract

Sb doped reactive sputtering-derived Pb(Zr, Ti)O₃ (Zr/Ti=48/52) thin films were investigated with the intention of improving ferroelectric properties. Also, the atomic valence of Sb in PZT thin film was confirmed as trivalent cation (Sb³⁺) by x-ray photoelectron spectroscopy (XPS). According to the tolerance factor t, Sb³⁺ tends to occupy the B-site of ABO₃ perovskite structure and acts as an acceptor that generates oxygen vacancies and holes. Transmission Electron Microscope(TEM) was used to observe the structural changes of PZT thin films by Sb addition. The leakage current densities and P_r of PZT thin films increased as the Sb contents increased. 0.7at% Sb doped PZT(PZST07) thin films exhibited improved fatigue properties (about 10% degradation of the remanent polarization after 10¹⁰ switching cycles).     

Effects of Substrate and Annealing Temperatures on the Characteristics of SrBi4Ti4O15 Thin Films

In this study, radio frequency (RF) sputtering was used as the method and the layer-structured bismuth compound of SrBi₄Ti₄O₁₅ + 4 wt% Bi₂O₃ ferroelectric ceramic was used as the target to deposit the SrBi₄Ti₄O₁₅ (SBT) thin films. The addition of excess Bi₂O₃ content in the target ceramic was used to compensate the vaporization of Bi₂O₃ during the sintering and deposition processes. SBT ferroelectric thin films were deposited on Pt/Ti/SiO₂/Si under optimal RF magnetron sputtering parameters with different substrate temperatures for 2 h. After that the SBT thin films were post-heated using rapid temperature annealing (RTA) method. The dielectric and electrical characteristics of the SBT thin films were measured using metal-ferroelectric-metal (MFM) structure. From the physical and electrical measurements of X-ray diffraction pattern, scanning electronic microscope (SEM), I-V curve, and C-V curve, we had found that the substrate temperature and RTA-treated temperature had large influences on the morphology, the crystalline structure, the leakage current density, and the dielectric constant of the SBT thin films.     

Ferroelectric Properties of Bi3.25Nd0.75Ti3O12 Thin Films Prepared by MOD Process

Ferroelectric Bi_{4 – x}Nd_xTi₃O₁₂(BNdT) thin films with the composition (x = 0.75) were prepared on Pt/Ti/SiO₂/Si(100) substrate by metal-organic deposition. The films were annealed by various temperatures from 550 to 650C and then the electrical and structural characteristics were investigated for the application of FRAM. Electrical properties such as dielectric constant, 2Pr and capacitance were quite dependent on the thermal heat treatment. The measured 2Pr value on the BNdT capacitor annealed at 650C was 56 C/cm² at an applied voltage of 5 V. No fatigue was observed up to 8 × 10¹⁰ read/write switching cycles at a frequency of 1 MHz regardless of annealing temperatures.     

CHARACTERISTIC OF (100)-TEXTURED (PbxSr1 −x)TiO3 THIN FILMS USED FOR DRAM AND TUNABLE DEVICE APPLICATION

ABSTRACT

The (Pb_xSr_1-x)TiO₃ (PST) thin films were deposited on LaNiO₃ (LNO(1 0 0))/ Pt/Ti/SiO₂/Si substrates electrode by RF-magnetron sputtering using three different Pb target composition ranging from 32.5%～37.5% and different process condition. Structural and dielectric properties of the PST thin films for tunable microwave and DRAM application were investigated. The PST thin films deposited at 400°C show higher dielectric constant than those post-annealed at 600°C because of better crystallization. The former also have lower leakage current around 10^?8 A/cm² up to applied field of 350 kv/cm, which is suitable for DRAM application. On the other hand, the post-annealed PST thin films have satisfactory tunability around 58% and figure of merit around 30, which are more suitable for microwave device application.