Three types of major process-induced damage which hampers the realization of FRAM (ferroelectric random access memory) device are investigated; dry etching induced damage, hydrogen-induced degradation, and stress effect. Since ferroelectric capacitors utilize the movement of body-centered atoms in perovskite structure, Ti or Zr in the case of Pb(Zr/x Ti/1-x)O³ (PZT), the movement can be suppressed or inhibited by many factors such as space charges, defects, chemical reactions, and stress of stacked layers. Unlike conventional silicon processes, the integration of ferroelectric capacitor module requires high density plasma to pattern their shapes because of a low volatility of etched byproducts, therefore the degradation of ferroelectric capacitor performance could occur by the collision of high energetic particles. The damage of PZT thin film due to dry etching process was characterized in terms of the microstructure and electrical properties. The damaged layer seems to be amorphous and the thickness is about 10 nm. The existence of such a layer in Pt/ PZT/Pt ferroelectric capacitor tends to increase the coercive voltage and the leakage current. The damaged layer was not fully reverted to perovskite phase by the thermal annealing, even at PZT formation temperature. For the elimination of this damaged layer, a novel wet cleaning solution was designed. Scanning electron microscopy (SEM) pictures clearly show that treatment with the cleaning solution completely removed the etching damaged layer. With the cleaning solution, a sidewall cleaning process and a surface cleaning process were proposed to eliminate non-ferroelectric phases such as pyrochlore, PbO, and etching damaged layer. After removing the non-ferroelectric phases, ferroelectric properties such as remnant polarization, coercive voltage, and leakage current were remarkably improved. In addition, the wet cleaned ferroelectric capacitors yielded superior endurance against hydrogen-induced damage compared to those of the non-cleaned capacitors. Several parameters such as Zr/Ti compositional ratios, excess amounts of Pb, the domain poling state, and electrode structures (Pt/PZT/Pt and Ir/IrO₂/PZT/Pt/IrO₂) were investigated in terms of hydrogen-induce degradation. It was found that the hydrogen-induce degradation is enhanced when PZT films have high compositions of Ti and Pb, and can be suppressed by domain poling prior to the hydrogen anneal. From the SIMS analysis and hysteresis loop shifts, it can be concluded that the hydrogen damage occurs mainly at the PZT/electrode interface and results in the development of negative charge buildup. To reduce the hydrogen-induced damage, an electron cyclotron resonance (ECR) oxygen plasma treatment of the Pt/PZT/Pt capacitor was attempted. It was found that oxygen plasma treatment modifies the surface of Pt electrodes. Surface modification alleviates catalytic activity of Pt electrodes, thereby significantly improving ferroelectric properties such as remnant polarization and leakage current. It seems that highly reactive oxygen radicals in ECR plasma play an important role in suppressing the catalytic activity of Pt electrodes. The cause of the blister formation on the PECVD (plasma enhanced chemical vapor deposition) SiO2/Pt/PZT/Pt capacitor was studied by means of annealing in various ambient. The blisters were observed at a temperature of 325°C in an O₂ atmosphere, while in a N2 and an Ar atmosphere blisters were not produced even at 500°C. Hydrogen evolution analysis from PECVD SiO2 layer showed a sharp peak near 320°C. The results indicate that the accumulation of water vapor pressure, developed via a chemical reaction between oxygen and hydrogen could be the dominant factor for blister formation in PECVD SiO₂/Pt/PZT/Pt capacitors. The effect of stress was investigated with two different interlayer dielectric (ILD) materials, ECR CVD Oxide and PECVD TEOS Oxide (PE-TEOS). Since the stress of PZT capacitor strongly depends on the ILD deposition temperature, the PZT capacitor with PE-TEOS showed more compressive stress than that with ECR oxide, which results in severe remnant polarization (Pr) degradation of PZT capacitor with PE-TEOS. This large stress effect of PE-TEOS was confirmed by measuring d-spacing values of (111) PZT films with XRD technique. These results suggest that the low ILD deposition temperature is a key parameter for achieving an ILD integration with a minimal Pr degradation. / Ph. D.

BMGs (bulk metallic glasses) exhibit many exceptional advantages for engineering applications, such as high strength, good corrosion resistance, etc. Despite of having these excellent properties, the brittle nature of metallic glasses in the bulk and thin film forms inevitably imposes limitation and restricts the wide application of BMGs and TFMGs. Composite concept might be another idea to solve this dilemma. In order to manufacture the bulk metallic glass composites (BMGCs), the approaches are classified into two categories: the intrinsic and extrinsic methods. For the intrinsic method, the in situ process and heat treatment process are two kinds of ways in common uses. Adding reinforcements into the BMGs or TFMGs is extensively used to manufacture composites in the extrinsic method. In this study, the deformation behaviors of multilayer (amorphous/nanocrystalline) micropillars are studied by uniaxial microcompression tests at room temperature. The nanocrystalline layer to be coupled with the amorphous layer can be of either face-centered cubic (FCC), hexagonal close-packed (HCP) or body-centered cubic (BCC) in crystal structure. The current study demonstrates that brittle problem of a metallic glass coating can be alleviated by percolating with a nanocrystalline metallic underlayer. The brittle thin film metallic glass can become highly ductile and exhibit a plastic strain over 50% at room temperature. The present study has an important implication for MEMS applications, namely, the life span of a brittle amorphous layer can be significantly improved by using an appropriate metallic underlayer. The brittle problem of thin film ZrCu metallic glasses was also treated by invoking soft Cu layers with optimum film layer thickness. Such multilayered amorphous/crystalline samples exhibit superplastic-like homogeneous deformation at room temperature. It is found that the deformability of the resultant micropillars depends on the thickness of Cu layers. Microstructural observations and theoretical analysis suggest that the superplastic-like deformation mode is attributed to homogeneous co-deformation of amorphous ZrCu and nanocrystalline Cu layers because the 100 nm-thick Cu layers can provide compatible flow stress and ¡§plastic zone¡¨ size well matched with those of ZrCu amorphous layers. Besides, we also made attempts to investigate the critical sample size below which shear band localization would disappear and the sample can deform homogeneously. In situ TEM compression was conducted on amorphous ZrCu nanopillars to study shear band formation behavior. The nanopillar is 140 nm in diameter and with a taper angle of 3¢X. Experimental observations and simulations based on a free-volume model both demonstrate that the deformation was localized near the top of the tapered metallic glass pillar. Eventually, the interface nature of metallic glass amorphous/crystalline was characterized through evaluating its energy and validated by the mechanical response of micropillar with ~45o inclined interface under compression. The calculated results showed that the ZrCu/Zr interface energy resides several joules per meter square, meaning that the Zr/ZrCu interface is inherently strong. The high strong adhesion ability of ZrCu/Zr interface was further confirmed by shear fracture happening rightly within the Zr layers rather than along the interface when compressing the ZrCu/Zr micropillars with 45o inclined interface.

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Structures grown via self-assembly are a unique field in nanotechnology. The morphology of self-assembled structures is affected by the balance between kinetics and thermodynamics during growth. Hence structures with tailored morphologies and properties can be created with adjustments in growth conditions. In this thesis we study crystal nucleation and equilibration, for both real and model systems. The growth of thin bismuth films is investigated on three atomically flat surfaces; Mica, Molybdenum di Sulphide, and highly oriented pyrolitic graphite (HOPG). Films are grown under UHV conditions, and characterised using scanning electron microscopy and atomic force microscopy. For coverages of only a few monolayers, bismuth particles are found to aggregate into flat, isolated islands. Islands have characteristic heights and morphologies for each substrate. By altering the deposition flux and coverage, the island density and morphology can be manipulated. On HOPG substrates, planar islands grown at low flux are replaced by 1D structures at high temperature. These anisotopic structures result from an anisotropy in bond strengths at the crystal-vapour interface. Depositing Bi on HOPG substrates at low flux or high temperature conditions produces nanorods aligned (roughly) perpendicular to step edges on the graphite. The aspect ratios (ARs) of these 1D structures are found to increase as the deposition flux is lowered, or the substrate temperature is increased. The Arrhenius dependence of the AR is determined from experiment. A Kinetic Monte Carlo (KMC) model for high AR step-edge aggregates was developed, determining the likely growth mechanism for the nanorods. A scaling regime devised from the KMC results predicts the dependence of nanorod ARs on flux and temperature, and allows an estimation of the energy binding Bi dimers to the sides of nanorods. Thin films can also be grown via the self-assembly of atomic clusters. After deposition coalescence of clusters has implications for the film morphology, and properties. We use KMC simulations to investigate the coalescence of pairs of 3D atomic clusters (15000 to 130000 atoms in size) via lattice based surface diffusion. For early coalescence stages, the radius of the neck region connecting the two clusters is found to develop with a different powerlaw to classical theory. For later coalescence stages, when the nucleation of new atomic layers on facets of the cluster is required for further coalescence the temperature, cluster size, and cluster orientation all influence the coalescence. Equilibration times for clusters coalescing at high temperature are found to be limited by the dissociation of atomic layers.

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