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This paper focuses on describing the integration of ultrananocrystalline diamond (UNCD) coating on pure titanium-based dental implants (DIs) integrated with the surface pre-treatment by chemical-mechanical nano-structuring (CMNS) process. The combination of the UNCD coating with the CMNS metal surface treatment provides a transformational process to produce a new generation of metallic implants. CMNS promotes a uniform and dense titanium oxide interface and UNCD enables higher resistance to chemical-induced corrosion by oral fluids and enhanced bone attachment due to superior bone cell growth on C atoms (element of life in human DNA and cell). The main focus of the presented research is to establish the preliminary studies on the integration of the UNCD coating process on CMNS treated dental implants to promote corrosion resistance and biocompatibility. It is demonstrated that the CMNS process in the presence of an oxidizer (1M to be optimal) induces a tailored interface to promote UNCD coating capability through effective interface passivation leading to uniform surface coverage. The final implant product is observed to have improved corrosion potential and enhanced hydrophobicity indicating better biocompatibility providing the basis for a new generation of superior DIs. The findings can further be extended to the hip, knee, and other orthopedic metallic implants, which require major performance improvements, particularly in reducing or eliminating in-vivo body fluid-induced chemical corrosion.
Titanium is the metal of choice for many implantable devices including dental prostheses, orthopaedic devices and cardiac pacemakers. Titanium and its alloys are favoured for hard tissue replacement because of their high strength to density ratio providing excellent mechanical properties and biocompatible surface characteristics promoting in-vivo passivation due to spontaneous formation of a native protective oxide layer in the presence of an oxidizer. This study focuses on the development of a three-dimensional chemical, mechanical, surface nano-structuring (CMNS) process to induce smoothness or controlled nano-roughness on the bio-implant surfaces, particularly for applications in dental implants. CMNS is an extension of the chemical mechanical polishing (CMP) process. CMP is utilized in microelectronics manufacturing for planarizing the wafer surfaces to enable photolithography and multilayer metallization. In biomaterials applications, the same approach can be utilized to induce controlled surface nanostructure on three-dimensional implantable objects to promote or demote cell attachment. As a synergistic method of nano-structuring on the implant surfaces, CMNS also makes the titanium surface more adaptable for the bio-compatible coatings as well as the cell and tissue growth as demonstrated by the electrochemical and surface wettability evaluations on implants prepared by DI-water machining versus oil based machining.
Copper is a commonly used interconnect metal in microelectronic interconnects due to its exceptional electrical and thermal properties. Particularly in applications of the 2.5 and 3D integration, Cu is utilized in through-silicon-vias (TSVs) and flip chip interconnects between microelectronic chips for providing miniaturization, lower power and higher performance than current 2D packaging approaches. SnAg capped Cu pillars are a common high-density interconnect technology for flip chip bonding. For these interconnects, specific properties of the Cu surface, such as roughness and cleanliness, are an important factor in the process to ensure quality solder bumps. During electroplating, tight processing parameters must be met so that defects are avoided, and high bump uniformity is achieved. An understanding of the interactions at the solder and Cu pillar interface is needed, based on the electroplating parameters, to determine the best method for populating solder on the wafer surface. In this study, surface treatment techniques such as oxygen plasma cleaning were performed on the Cu surfaces and the SnAg plating chemistry for depositing the solder were evaluated through hull cell testing to qualitatively determine the range of current densities to investigate. It was observed that current density while plating played a large role in solder bump deposition morphology. At the higher current densities greater than 60 mA/cm2, bump height non-uniformity and dendritic growth are observed and at lower current densities, less than or equal to 60 mA/cm2, uniform, continuous bump height occurred.
The continuous trend of achieving more complex microelectronics with smaller nodes yet larger wafer sizes in microelectronics manufacturing lead to aggressive development requirements for chemical mechanical planarization (CMP) process. Particularly, beyond the 14 nm technology the development needs made it a must to introduce high mobility channel materials such as Ge. CMP is an enabler for integration of these new materials into future devices. In this study, we implemented a design of experiment (DOE) methodology in order to understand the optimized CMP slurry parameters such as optimal concentration of surface active agent (sodium dodecyl sulfate-SDS), concentration of abrasive particles and pH from the viewpoint of high removal rate and selectivity while maintaining a defect free surface finish. The responses examined were particle size distribution (slurry stability), zeta potential, material removal rate (MRR) and the surface defectivity as a function of the selected design variables. The impact of fumed silica particle loadings, oxidizer (H2O2) concentration, SDS surfactant concentration and pH were analyzed on Ge/silica selectivity through material removal rate (MRR) surface roughness and defectivity analyses.
Metal CMP applications necessitate the formation of a protective oxide film in the presence of surface active agents, oxidizers, pH regulators and other chemicals to achieve global planarization. Formation and mechanical properties of the chemically modified metal oxide thin films in CMP determine the stresses develop at the interfaces delineating the stability and protective nature of the chemically altered films on the surface of the metal wafer. The balance between the stresses built in the film structure versus the mechanical actions provided during the process can be used to optimize the process variables and furthermore help define new planarization techniques for the next generation microelectronic device manufacturing. In this study, the preliminary studies were concentrated on the very well established tungsten CMP applications and furthermore, titanium CMP applications were presented as a part of surface nano-structuring methodology for biomedical applications by stressing the synergistic effect of protective metal oxide film of titanium in this advanced application.
In this study, slurry formulations in the presence of self-assembled surfactant structures were investigated for Ge/SiO2 CMP applications in the absence and presence of oxidizers. Both anionic (sodium dodecyl sulfate-SDS) and cationic (cetyl trimethyl ammonium bromide-C12TAB) micelles were used in the slurry formulations as a function of pH and oxidizer concentration. CMP performances of Ge and SiO2 wafers were evaluated in terms of material removal rates, selectivity and surface quality. The material removal rate responses were also assessed through AFM wear rate tests to obtain a faster response for preliminary analyses. The surfactant adsorption characteristics were studied through surface wettability responses of the Ge and SiO2 wafers through contact angle measurements. It was observed that the self-assembled surfactant structures can help obtain selectivity on the silica/germanium system at low concentrations of the oxidizer in the slurry.
This study presents an effort to couple a wafer removal rate profile model based on the locally relevant Preston equation to the change in pad thickness profile which reflects to post polish profile of the wafers after Chemical Mechanical Planarization. The result is a dynamic predictor of how the wafer removal rate profile shifts as the pad ages. These predictions can be used to fine tune the conditioner operating characteristics without having to carry out high cost and time consuming experiments. The accuracy of the predictions is demonstrated by individual confirmation experiments in addition to the evaluation of the defectivity performance with the varied pad conditioning profiles.
Biomaterials are widely used for dental implants, orthopedic devices, cardiac pacemakers and catheters. One of the main concerns on using bio-implants is the risk of infection on the materials used. In this study, our aim is to quantify the effect of controlled surface roughness on the infection resistance of the titanium based bio-materials which are commonly used for orthopedic devices and dental implants. To modify the surface roughness of the surfaces in a controlled manner, Chemical Mechanical Polishing (CMP) technique, which is extensively used in semiconductor industry for the planarization of the interlayer dielectrics and metals, is utilized. To determine the infection resistance of the created films with varying surface roughness, bacteria growth response was studied on titanium plates after CMP.
The formulation of slurries for chemical–mechanical planarization (CMP) is currently considered more of an art than a science, due to the lack of understanding of the wafer, slurry, and pad interactions involved. Several factors, including the large number of input variables for slurries and the synergistic interplay among input variables and output parameters, further complicate our ability to understand CMP phenomena. This article provides a fundamental basis for the choice of chemical additives and particles needed for present-day and next-generation slurry design. The effect of these components on nanoscale and microscale interaction phenomena is investigated. Methodologies are suggested for the development of next-generation slurries required to overcome CMP challenges related to defectivity and the surface topography of soft materials such as Low-κ dielectrics and copper.
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