Advances in the interconnection technology have played a key role in the continued improvement of the integrated circuit (IC) density, performance and cost. Copper (Cu) metallization, dual damascenes processing and integration of copper with low dielectric constant material are key issues in the IC industries. Chemical mechanical planarization of copper (CuCMP) has emerged as an important process for the manufacturing of ICs. Usually, Cu-CMP process consists of several steps such as the removal of surface layer by mechanical action of the pad and the abrasive particles, the dissolution of the abraded particles in the CMP solution, and the protection of the recess areas. The CMP process occurs at the atomic level at the pad/slurry/wafer interface, and hence, slurries and polishing pads play critical role in its successful implementation. The slurry for the Cu-CMP contains chemical components to facilitate the oxidation and removal of excess Cu as well as passivation of the polished surface. During the process, these slurry chemicals also react with the pad. In the present study, investigations were carried out to understand the effect of hydrogen peroxide (H2O2) as an oxidant and benzotriazole (BTA) as an inhibitor on the CMP of Cu. Interaction of these slurry components on copper has been investigated using electrochemical studies, x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). In the presence of 0.1M glycine, Cu removal rate was found to be high in the solution containing 5% H2O2 at pH 2 because of the Cu-glycine complexation reaction. The dissolution rate of the Cu was found to increase due to the formation of highly soluble Cu-glycine complex in the presence of H2O2. Addition of 0.01M BTA in the solution containing 0.1M glycine and 5% H2O2 at pH 2 exhibited a reduction in the Cu removal rate due to the formation of Cu-BTA complex on the surface of the Cu further inhibiting the dissolution. XPS and SIMS investigations revealed the formation of such Cu-glycine complex, which help understand the mechanism of the Cu-oxidant-inhibitor interaction during polishing. Along with the slurry, pads used in the Cu-CMP process have direct influence an overall process. To overcome problems associated with the current pads, new application specific pad (ASP) have been developed in collaboration with PsiloQuest Inc. Using plasma enhanced chemical vapor deposition (PECVD) process; surface of such ASP pads were modified. Plasma treatment of a polymer surface results in the formation of various functional groups and radicals. Post plasma treatment such as chemical reduction or oxidation imparts a more uniform distribution of such functional groups on the surface of the polymer resulting in unique surface properties. The mechanical properties of such coated pad have been investigated using nanoindentation technique in collaboration with Dr. Vaidyanathan’s research group. The surface morphology and the chemistry of the ASP are studied using scanning electron microcopy (SEM), x-ray photoelectron spectroscopy (XPS), and fourier transform infrared spectroscopy (FTIR) to understand the formation of different chemical species on the surface. It is observed that the mechanical and the chemical properties of the pad top surface are a function of the PECVD coating time. Such PECVD treated pads are found to be hydrophilic and do not require being stored in aqueous medium during the not-in-use period. The metal removal rate using such surface modified polishing pad is found to increase linearly with the PECVD coating time. Overall, this thesis is an attempt to optimize the two most important parameters of the Cu-CMP process viz. slurry and pads for enhanced performance and ultimately reduce the cost of ownership (CoO).

Biomedical implants are commonly made from commercially pure titanium and other metal alloys, which are chosen for their strength and density. To improve the stability and promote bone cell growth into the implant, efforts to bond coatings to metal have been extensively studied. Many coatings used are considered bioactive, which promote the adhesion and growth of the bone cells surrounding the implant [A.1]. Of these, the most commonly investigated coating is a ceramic called hydroxyapatite, which is brittle, leading to flaking and inadequate bone cell growth [A.2]. Alternate bioactive coatings are being examined, including chitosan, the deacetylated form of chitin. Chitin is the second most abundant polymer in nature [A.3] and is found in the exoskeletons of insects and shellfish [A.4]. Chitosan has been proven to have excellent biocompatibility [A.5], be non-toxic [A.3], and promote the adhesion and growth of bone cells [A.6 ? A.7]. In this research, four treatment combinations were developed and tested in an attempt to improve film bonding. These treatment combinations were created using one of two silane molecules, aminopropyltriethoxysilane and triethoxsilylbutyraldehyde, and one of two metal treatments, passivation and piranha treatment. XPS was used to characterize the reaction steps for each of the treatment combinations. A significant decrease in TiO, along with significant increases in SiOx groups, C ? N ? H, and C = O, indicated that the reactions were proceeding as expected. XPS also indicated that, chemically, the chitosan films were not significantly different and were unchanged by the treatment combinations. Following chemical analysis, mechanical testing was performed on the four treatment combinations. No changes to the bulk properties were seen as demonstrated by nano-indentation, further indicating that the four treatment combinations did not change the chemical properties of chitosan. The bulk adhesion of the films was greatly improved for all four treatment combinations, as demonstrated by tensile testing. The highest value from this research, 19.50 ± 1.63 MPa, was significantly higher than the previously published results of 1.6 ? 1.8 MPa [A.10]. Overall, the treatments developed in this study significantly improved the adhesion of the chitosan film on the titanium substrate, without modifying the chemical or structural properties of chitosan. [A.1] Ratner, B. D. and A. S. Hoffman. Biomaterials Science: An Introduction to Materials in Medicine. California: Academic Press, Inc., 1996, Foreword, 1-8. [A.2] S.D. Cook, K.A. Thomas, J.F. Kay. ?Experimental Coating Defect in Hydroxylapatite-Coated Implants.? Clinical Orthopaedics and Related Research, 1992, 265, 280-290. [A.3] A.K. Singla, M. Chawla. ?Chitosan: some pharmaceutical and biological aspects- an update.? Journal of Pharmacy and Pharmacology, 2001, 53, 1047-1067. [A.4] Q. Li, E.T. Dunn, E.W. Grandmaison, M.F.A. Goosen. ?Application and Properties of Chitosan.? Journal of Bioactive and Compatible Polymers, 1992, 7, 370-397. [A.5] M. Prasitsilp, R. Jenwithisuk, K. Kongsuwan, N. Damrongchai, P. Watts. ?Cellular responses to chitosan in vitro: The importance of deacetylation.? Journal of Materials Science: Materials in Medicine, 2000, 11, 773-778. [A.6] R.A.A. Muzzarelli, M. Mattioli-Belmonte, A. Pugnaloni, G. Biagini. ?Biochemistry, histology, and clinical uses of chitins and chitosans in wound healing.? Chitin and Chitinases, ed. P. Jolles, R.A.A. Muzzarelli, Switzerland: Birkhauser Verlag Basel, 1990. [A.7] P. Klokkevold, L. Vandemark, E.B. Kenney, G.W. Bernard. ?Osteogenesis Enhanced by Chitosan (Poly-N-Acetyl Glucosaminoglycan) In Vitro.? Journal of Periodontology, 1996, 67, 1170-1775. [A.8] J.D. Bumgardner, R. Wiser, P.D. Gerard, P. Bergin, B. Chestnutt, M. Marini, V. Ramsey, S.H. Elder, J.A. Gilbert. ?Chitosan: potential use as a bioactive coating for orthopaedic and craniofacial/dental implants.? Journal of Biomaterials Science, Polymer Edition, 2003, 14 (5), 423-438.

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No description available.

<p>Fabrication of microarrays using sol-gel immobilization has been utilized as an approach to develop high density biosensors. Microarray fabrication using various printing techniques including pin-printing and piezoelectric ink jet printing methods has been demonstrated. However, only limited characterization to understand the encapsulated biomolecule-material interface has been reported. Herein, Chemical characterization using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) on pin-printed microarrays of sol-gel derived acetylcholinesterase (AChE) microarrays is reported. Furthermore, the <em>in situ</em> fabrication of microarrays following the sol-gel process using piezoelectric ink jet printing methods was explored. Through techniques measuring solution viscosity, surface tension and particle size, important aspects of bio-ink formulation for piezoelectric ink jet printing were identified. Combined, a greater understanding towards the fabrication and characterization of sol-gel derived microarrays was achieved through this exploratory research.</p> / Master of Science (MSc)

The field of condensed matter computational physics has seen an explosion of applicability over the last 50+ years. Since the very first calculations with ENIAC and MANIAC the field has continued to pushed the boundaries of what is possible; from the first large-scale molecular dynamics simulation, to the implementation of Density Functional Theory and large scale Car-Parrinello molecular dynamics, to million-core turbulence calculations by Standford. These milestones represent not only technological advances but theoretical breakthroughs and algorithmic improvements as well. The work in this thesis was completed in the hopes of furthering such advancement, even by a small fraction. Here we will focus mainly on the calculation of electronic and structural properties of solids and liquids, where we shall implement a wide range of novel approaches that are both computational efficient and physically enlightening. To this end we routinely will work with maximally localized Wannier functions (MLWFs) which have recently seen a revival in mainstream scientific literature. MLWFs present us with interesting opportunity to calculate a localized orbital within the planewave formalism of atomistic simulations. Such a localization will prove to be invaluable in the construction of layer-based superlattice models, linear scaling hybrid functional schemes and model quasiparticle calculations. In the first application of MLWF we will look at modeling functional piezoelectricity in superlattices. Based on the locality principle of insulating superlattices, we apply the method of Wu et al to the piezoelectric strains of individual layers under iifixed displacement field. For a superlattice of arbitrary stacking sequence an accurate model is acquired for predicting piezoelectricity. By applying the model in the superlattices where ferroelectric and antiferrodistortive modes are in competition, functional piezoelectricity can be achieved. A strong nonlinear effect is observed and can be further engineered in the PbTiO 3 /SrTiO 3 superlattice and an interface enhancement of piezoelectricity is found in the BaTiO 3 /CaTiO 3 superlattice. The second project will look at The ionization potential distributions of hydrated hydroxide and hydronium which are computed within a many-body approach for electron excitations using configurations generated by ab initio molecular dynamics. The experimental features are well reproduced and found to be closely related to the molecular excitations. In the stable configurations, the ionization potential is mainly perturbed by solvent water molecules within the first solvation shell. On the other hand, electron excitation is delocalized on both proton receiving and donating complex during proton transfer, which shifts the excitation energies and broadens the spectra for both hydrated ions. The third project represents a work in progress, where we also make use of the previous electron excitation theory applied to ab initio x-ray emission spectroscopy. In this case we make use of a novel method to include the ultrafast core-hole electron dynamics present in such situations. At present we have shown only strong qualitative agreement with experiment. / Physics

The chemical adsorption and reaction of methyl fluoride, methyl chloride, methyl bromide, methyl iodide, methyl sulfide, dimethyl sulfide, dimethyl disulfide, and bis(trifluoromethyl) disulfide on clean, polycrystalline nickel surface (at 25°C) were investigated using an X-ray photoelectron spectrometer (XPS) and a thermal desorption system with mass spectrometric analysis (TD). The ion implantation of the methyl halide series on nickel was investigated by XPS. The nickel surface was cleaned by high temperature heating in vacuum or argon ion sputtering. An industrial lubricant, FC-43 (tri-hepta-fluorobutyl amine), was adsorbed on a gold-plated nickel surface at 25°C. Tne FC-43 adsorption system was investigated by TD. The adsorption of the methyl halide series on nickel was predominantly dissociative with several co-existing surface species being observed. The XPS results show that two carbon and two halogen species are formed. The possible structures for carbon are a CH₃-type and a CH₂-type or CH_nX (n = 0-3) adsorbed species. The halogen species appear to be neutral and ionic species. The TO results support the dissociative adsorption process for methyl halides on nickel. The adsorption of methyl fluoride and methyl chloride on nickel studied by TD resulted in the corresponding nickel halide being detected. The adsorption of methyl bromide and methyl iodide on nickel studied by TO resulted in the corresponding hydrogen halide, HX, being detected. The XPS results of the ion implantation of the methyl halides resulted in only one type of carbon that is similar to graphite. A halide type of halogen was also formed upon ion implantation. The XPS results for the adsorption of methyl sulfide, dimethyl sulfide, and dimethyl disulfide on nickel showed that only one carbon and one sulfur were observed. The possible structure for carbon is a CH₃-type of adsorbed specie. lhe sulfur species appears to be a sulfide S⁼-type adsorbed specie. The XPS results for the adsorption of bis(trifluoromethyl) disulfide on nickel showed that only sulfur was observed on the nickel surface. The TD results- for the methyl sulfide adsorption process was shown to be predominantly an associative type. The TO results for the dimethyl sulfide adsorption process were a mixture of dissociative and associative adsorption processes. The dimethyl disulfide adsorption process was determined by TD to be predominantly a dissociative type. The bis(trifluoromethyl} disulfide was determined by TD to be completely dissociative upon adsorption and reacted with nickel to form nickel sulfide. The TD results of FC-43 adsorption on gold-plated nickel showed that the predominant adsorption process was the associative type. / Ph. D.

In this study the applicability of Carbon-13 NMR and XPS to the detection of chemical changes in a solid composite rocket propellant was studied. Storage at elevated temperatures was used to simulate the propellant ageing process. In the XPS analysis, changes in the sources for the N(1s) and Cl(2p) photopeaks were investigated. The propellant loses "organic" nitrogen as it ages. Changes in the amount of Cl⁻ present are in doubt due to instrumental considerations. Carbon-13 NMR analysis showed that with increasing age of a sample there is a corresponding loss of vinylic groups from the binder. This loss of vinylic character is preferential in the order pendant>>cis>trans. Due to the long scan times involved this method is of limited utility for ageing analysis. / Master of Science

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Bipolar electrochemistry is an interesting concept for high throughput screening techniques due to the ability to induce gradients in a range of materials and their properties, such as composition, particle size, or dopant levels, among many others. One of the key advantages of the method is the ability to test, create or modify materials without the need for a direct electrical connection. In this thesis, the viability of this method has been explored for a range of possible applications, such as metal recycling, nanoparticle modification and corrosion analysis. In the initial part of the work a process to electrodeposit gradients in metal composition was evaluated, with a view to applying the technique to the extraction and recycling of metals from fly ash. Compositional gradients in the metals under study could be readily obtained from controlled reference solutions, although the spatial resolution of the metals was not sufficient to perform separation. Only copper could be easily deposited from the fly ash solution. Bipolar electrodeposition was also successfully used to modify the particle size across substrates decorated with gold nanoparticles. The approach was demonstrated both for surfaces possessing either a uniform particle density or a gradient in particle density. In the latter case samples with simultaneous, orthogonal gradients in both particle size and density were obtained. A combination of the bipolar approach with rapid image analysis was also evaluated as a method for corrosion screening, using quantitative analysis of gradients in pitting corrosion damage on stainless steels in HCl as a model system. The factors affecting gradient formation and the initiation of corrosion were thoroughly investigated by the use of a scanning droplet cell (SDC) technique and hard x-ray photoelectron spectroscopy (HAXPES). The ability to screen arrays of different materials for corrosion properties was also investigated, and demonstrated for stainless steel and Ti-Al alloys with pre-formed compositional gradients. The technique shows much promise for further studies and for high throughput corrosion screening applications.