In this study, the reactive rf magnetron sputtering was used to deposit Ba(Ti0.9,Zr0.1)O3 (BZT) ferroelectric thin films on Pt/SiO2/Si and SiO2/Si substrates, and MFMIS and MFIS structures are fabricated. The effects of various sputtering parameters on the characteristics of thin films, such as the oxygen concentrations, rf power and deposition time are discussed. The physical characteristics of BZT thin films were obtained by the XRD pattern and AFM morphology. The variations of crystallization and surface roughness of thin films were discussed. The electrical properties of BZT thin films deposited under various sputtering parameters are measured by the HP4284A and HP4156C. From the experimental results obtained, the optimal dielectric constant and leakage current density were 197 and 1.41¡Ñ10-7A/cm2, respectively, under the applied electrical field of 0.5 MV/cm. In addition, the coercive field and remanent polarization were 30 kV/cm and 7 £gC/cm2 from the P-E curves, respectively. In addition, the electrical characteristics of MFMIS and MFIS structures are discussed. Besides, the memory window and leakage current density of thin films deposited at various sputtering parameters on MFIS structure are also discussed.

Recently, many kinds of memory devices had been discussed, such as static random access memory (SRAM), dynamic random access memory (DRAM), the flash memory, ferroelectric random access memory (FRAM), magnetron random access memory (MRAM) and etc. In the volatile and nonvolatile memories, the non-destructive readout feature of high density nonvolatile memories will play an important role in the future. The structure characteristics of nonvolatile FeRAM with non-destructive metal-ferroelectric-insulator-semiconductor (MFIS) and metal-ferroelectric-metal-insulator-semiconductor (MFM) structures would be discussed in this study. Among many ferroelectric materials, such as pervoskite (ABO3) and bi-layer ferroelectric (BLFS) structures had been widely investigated and discussed for applications in non-volatile ferroelectric random access memory devices. However, the ferroelectric materials such as (Ba,Sr)TiO3 and Ba(Ti,Zr)O3 thin films were expected to substitute the PZT or SBT memory materials and improve the environmental pollution because of their lower pollution problem. According to system on panel (SOP) concept, the switch characteristics of various thin-film transistors had been widely investigated for the amorphous silicon (a-Si) and poly-crystaline silicon (poly-Si) active matrix LCD (AM-LCD) display applications. Therefore, the integrated electronic devices such as memory device, control device, central processing unit (CPU) and etc will be important research and study in the future. According the statement, we would investigate that the ferroelectric Ba(Zr0.1Ti0.9)O3 (BZT) composition could be used in a one-transistor-capacitor (1TC) structure of the amorphous-Si TFT device to replace the gate oxide of random access memory devices. In this study, the rf magnetron sputtering was used to deposit BZT ferroelectric thin films on Pt/Ti/SiO2/Si and ITO/glass substrates, and MFM and MFIS structures were also fabricated. The effects of various sputtering parameters on the physical and electrical characteristics of BZT thin films such as the oxygen concentrations, rf power, substrate temperature, chamber pressure and deposition time were discussed. From the XRD, AFM and SEM analysis, the various peaks, surface roughness, grain size and thickness of as-deposited BZT thin film were also found. From the C-V and J-E curves of MFM and MFIS structures, the maximum capacitance, dielectric constant, memory window and leakage current density were obtained. After rapid thermal annealing (RTA), the capacitances, remanent polarization (P-E) curves and leakage current density of MFM structure in Pt/Ti/SiO2/Si and ITO/glass substrates were improved. In addition, we found that the higher capacitance, larger memory windows and lower leakage current density of BTV/BZT dual layer structure using annealed BZT films would be increased in this study. Finally, the one-transistor-capacitor (1TC) structure of ferroelectric random access memory (FeRAM) with the gate oxide of BZT thin films on the amorphous silicon TFT structure have been fabricated and investigated. The Ion/Ioff drain current ratio, drain current window, ID-VG, ID-VD curves, threshold voltage (VT) and subthreshold swing (SS) properties of 1TC bottom-gated FeRAM device were obtained under the linear and saturation region. From the results in this study, the BZT thin films for bottom-gated amorphous thin-film transistor will be a suitable candidate to fabricate with ferroelectric random access memory (FeRAM) devices for system on panel (SOP) applications.

In this study, the reactive rf magnetron sputtering was used to deposit Ba(Zr0.1,Ti0.9)O3 (BZT) ferroelectric thin films on ITO/Glass substrate, and MFM structure was fabricated. The effects of various sputtering parameters on the characteristics of thin films, such as the oxygen concentrations, substrate temperature, rf power and chamber pressure were discussed, and then the optimal sputtering parameters were determined. The annealing process of rapid thermal annealing (RTA) and conventional thermal annealing (CTA) were used to promote the ferroelectric characteristics. The physical characteristics of BZT thin films were obtained by the analyses of SEM, XRD patterns and AFM morphologies. The surfaces, cross-section, crystallization and surface roughness of thin films were discussed. To investigate the electrical properties, the capacitance-voltage (C-V), current-voltage (I-V) and P-E hysteresis characteristics of BZT thin films were measured by the HP4284A impedance analyzer, HP4156C semiconductor parameter analyzer and computerized radiant technology (RT66), respectively. Furthermore, characteristics of the MFM structure were discussed. From the experimental results, the dielectric constant with optimal sputtering parameters was about 84, and the leakage current of thin film was about 6 ¡Ñ 10-8 A/cm2 when the applied electrical field of thin film was at 0.4 MV/cm. The remanent polarization (Pr) and coercive field (Ec) were 2.87 £gC/cm2 and 259 kV/cm from the P-E hysteresis loops, respectively. In addition, the ferroelectric characteristics of the thin film could be improved after rapid thermal annealing at 550¢J for 3 minutes. The remanent polarization (Pr), coercive field (Ec) and saturated polarization (Ps) were 3.42 £gC/cm2, 266 kV/cm and 6.99 £gC/cm2, respectively.

In this study, the electrical properties of [Al/(Bi4Ti3O12+V2O5 ) /Ba(Zr0.1Ti0.9)O3/Silicon¡AMFIS ]structure using annealed-BZT films would be improved for the nonvolatile FeRAM device applications. The radio-frequency magnetron sputtering was used to deposit BTV ferroelectric films on Mo/Ti/SiO2/Si and BZT/Si substrates, respectively, and MFMIS and MFIS structures would also be fabricated. The various sputtering parameter effects of BTV films such as the oxygen concentrations, rf power and deposition time would be discussed. Besides, the electrical and physical properties of as-deposited BZT films for (BTV/BZT/Si¡AMFIS) structure would be improved by different rapidly thermal annealing temperature. The physical characteristics of BTV films and annealed-BZT films for various sputtering parameters were obtained from the XRD pattern and SEM morphology. Besides, the memory window, dielectric constant and leakage current of MFM and MFIS structure using BTV films and annealed-BZT films would be found from the HP4284A, RT66A and HP4156C. From the experimental result obtained, the maximum dielectric constant of BTV films for 40 % oxygen concentration and 130W power were 10.79. The leakage current density was about 10-5A/cm2, as the applied electrical field of 200 kV/cm. In addition, the coercive field (Ec) and remanent polarization (2Pr) were 750 kV/cm and 12 £gC/cm2 from the P-E curves, respectively. Finally, the maximum memory window and lower leakage current density of [Al/(Bi4Ti3O12+V2O5) /Ba(Zr0.1Ti0.9)O3/Silicon¡AMFIS) structure would be found and they were 25V and 10-8A/cm2, respectively.

The polarization reversal in ferroelectric HfO₂ is adopted to store information in three distinct device classes - ferroelectric field effect transistors (FeFET), ferroelectric capacitors (FeCAP) and ferroelectric tunnel junctions (FTJ). Common to all three concepts is the adoption of a ferroelectric layer stack that acts either as gate dielectric in the FeFET or as the capacitor dielectric and tunneling barrier in the FeCAP or FTJ, respectively. A composite structure including an inevitably or purposefully formed dielectric layer is frequently adopted. In this work we report on the co-existence of all three memory concepts within one device structure and propose a 2T1C ferroelectric memory cell that allows the operation and comparative characterization of the trinity of ferroelectric memory devices.

During the last decade ferroelectrics based on doped hafnium oxide emerged as promising candidates for realization of ultra-low-power non-volatile memories. Two spontaneous polarization states occurring in the material that can be altered by applying electrical fields rather than forcing a current through and the materials compatibility to CMOS processing are the main benefits setting the concept apart from other emerging memories. 1T1C ferroelectric random access memories (FeRAM) as well as 1T FeFET concepts are under investigation. In this article the application of hafnium based ferroelectric memories in different flavours and their ranking in the memory landscape are discussed.

With the discovery of the ferroelectric (FE) properties within HfO₂, the scaling gap between state-of-the-art technology nodes and non-volatile memories based on FE materials can be bridged. In addition to non-volatility, new memory concepts should guarantee sufficient endurance and operation stability. However, in contrast to optimized perovskite based FEs, binary oxide based FE memories still show changes in the memory window (MW) followed by either hard breakdown or closure of the MW. Recently, we have shown that anti-FE (AFE) materials exhibit very stable and significantly higher endurance with respect to the FE counterparts. Inspired by the robustness and remarkable cycling performance of the AFE materials, we analyze the remaining reliability aspects of these devices. By characterizing the pure film properties of capacitor stacks and switching performance when integrated into devices, we compare and investigate temperature stability, imprint, retention, and variability of both FE and AFE memories. We investigate if the lower energetic barrier to be overcome together with partial switching and lower switching induced stress are responsible for the higher endurance of the AFE with respect to the FE based memories. By utilizing charge trapping and charge pumping tests together with leakage current spectroscopy in combination with comprehensive modeling we check that assumption. Moreover, we identify the interfacial buffer layer as the weakest link of these devices.

Le développement industriel de la technologie FeRAM (assurant non volatilité, accès rapide et faible consommation) est aujourd'hui limité par la fiabilité du condensateur ferroélectrique intégré. Le travail de thèse, axé sur la compréhension de ses modes de défaillance, a consisté à associer des analyses électriques et microstructurales sur des condensateurs élémentaires, des véhicules de test et des composants. La dégradation des propriétés ferroélectriques de condensateurs élémentaires, sous stresses électriques, a été corrélée à leurs évolutions microstructurales. L'irradiation X s'est également avérée un facteur accélérateur de cette dégradation. Sur les objets technologiques avancés, les techniques synchrotron et la microscopie électronique, associées aux tests de fiabilité, ont permis de corréler les modes de défaillance à la nature du condensateur, à sa géométrie (planaire ou 3D) et aux étapes technologiques utilisées.

Avec l’usage intensif de dispositifs microélectroniques modernes, il existe un besoin croissant de mémoires non volatiles. La FeRAM (mémoire ferroélectrique à accès aléatoire) est une des mémoires de nouvelle génération les plus prometteuses en raison de sa faible consommation et de sa vitesse élevé de lecture/écriture. Parmi les différents matériaux ferroélectriques, le PZT (Pb (Zr1-x,Tix)O3) présente une polarisation rémanente élevée et un faible champ coercitif qui en font un candidat de choix pour les FeRAM.Dans cette thèse, la croissance épitaxiale de couches de PZT (52/48) d’épaisseurs variables (33 à 200 nm), sur un substrat de SrTiO3 et une électrode inférieure interfaciale de SrRuO3, a été réalisé par deux méthodes pour comparaison : pulvérisation cathodique et sol – gel. Trois matériaux conducteurs différents (SrRuO3, Pt et ITO) ont été utilisés comme électrode supérieure. L’objectif a été une étude détaillée des propriétés électriques et ferroélectriques de ces structures MFM (métal-ferroélectrique-métal), avec une attention particulière sur l’influence des conditions d’élaboration et de la nature des électrodes sur le courant de fuite et la dynamique de basculement de domaines.Les capacités élaborées par pulvérisation ou sol-gel présentent des caractéristiques semblables : Au-delà d’une épaisseur minimum d’environ 100 nm, pour une structure capacitive à base de PZT de 100 × 100 μm2, elles montrent un faible courant de fuite, une permittivité relative maximale élevée (600 - 1300) et une polarisation rémanente élevée (30 - 40 μC/cm2). Les mécanismes dominants dans le courant de fuite ont été identifiés par un fit des résultats, manifestant différentes contributions en fonction du champ électrique. Des caractérisations par PFM (microscopie à force piézoélectrique) confirme l’existence de domaines ferroélectriques de directions opposées. Il est aussi montré que le champ coercitif dépend fortement de la fréquence de travail. D’autre part, les propriétés d’impression dépendent de l’électrode supérieure, de la nature du recuit et de l’épaisseur de l’électrode inférieure. / With the intensive use of modern microelectronic devices in numerous areas, there is an increasing demand for non-volatile memories. FeRAM (ferroelectric random access memory) is one of the most potential next-generation memories for its ultra-low power consumption and high read/write rate. Among various ferroelectrics, PZT (Pb(Zr1-x,Tix)O3) exhibits high remnant polarization and low coercive field, which make it a promising candidate for FeRAM.In this dissertation, PZT(52/48) layers of various thicknesses (from 33 nm to 200 nm) have been epitaxially grown on SrTiO3 substrate, with a SrRuO3 interlayer as bottom electrode, using two deposition methods for comparison: sol-gel and sputtering. Three different conductive materials (SrRuO3, Pt and ITO) have been deposited as top electrode. The objective was a detailed study of the electrical and ferroelectric properties of these MFM (metal-ferroelectric-metal) capacitors, with a particular investigation of the influence of elaboration conditions and electrode material on leakage currents and domain switching dynamics.Sputtered and sol-gel-derived PZT capacitors showed similar properties: Above a minimum workable thickness of about 100 nm for a 100 × 100 μm2 PZT capacitor, they showed low leakage current, high maximum relative permittivity (600 - 1300) and high remnant polarization (30 - 40 μC/cm2). The dominant leakage current mechanisms were identified by fitting the results, showing different contributions as a function of electric field. PFM (piezoresponse force microscopy) characterizations confirmed the existence of ferroelectric domains of opposite directions. Coercive field was found to be highly dependent on work frequency. Besides, imprint properties were found to be dependent on top electrode, annealing procedure and bottom electrode thickness.

A 2T2C ferroelectric memory cell consisting of a select transistor, a read transistor and two ferroelectric capacitors that can be operated either in FeRAM mode or in memristive ferroelectric tunnel junction mode is proposed. The two memory devices can be programmed individually. By performing a combined readout operation, the two stored bits of the memory cells can be combined to perform in-memory logic operation. Moreover, additional input logic signals that are applied as external readout voltage pulses can be used to perform logic operation together with the stored logic states of the ferroelectric capacitors. Electrical characterization results of the logic-in-memory (LiM) functionality is presented.