Person: BAŞIM DOĞAN, Gül Bahar
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Gül Bahar
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BAŞIM DOĞAN
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Conference paperPublication Metadata only Advanced slurry formulations for new generation chemical mechanical planarization (CMP) applications(Cambridge University Press, 2012-01) Başım, Gül Bahar; Karagöz, Ayşe; Özdemir, Zeynep; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe; Özdemir, ZeynepChemical Mechanical Planarization (CMP) is widely used to ensure planarity of metal and dielectric surfaces to enable photolithography and hence multilevel metallization in microelectronics manufacturing. The aim of this study is to establish a fundamental understanding on the dynamic growth of nano-scale protective oxide thin films during CMP to enable the selection of proper oxidizer concentrations for slurry formulations. Tungsten was selected as the model metal film to study the formation of these metal oxide films in various oxidizers and Atomic Force Microscope (AFM) was used to measure the surface roughness of the samples conditioned in the oxidizer environment before and after the CMP was conducted. The affect of surface roughness on wettability of the surfaces were also studied through contact angle measurements on the treated tungsten films. Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance FTIR/ATR technique in combination with the X-Ray Reflectivity (XRR) were utilized to determine the thicknesses of the oxidized nano films on the tungsten surface. The results were evaluated through the material removal responses reported in the literature for the W-CMP in addition to the comparison of the Pilling-Bedworth ratios of the oxidized nano films to determine the ability of the created oxide film as a self-protective oxide.ArticlePublication Metadata only Effect of slurry aging on stability and performance of chemical mechanical planarization process(Elsevier, 2011-03) Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharChemical mechanical planarization (CMP) is known to be one of the most challenging processes in microelectronics manufacturing due to the number of variables involved in the design of the process. In particular, the slurries made of nano-sized particles and aggressive chemistries need to be characterized batch to batch and as a function of time to enable robust high volume manufacturing. In this study, the effect of slurry aging on CMP performance was investigated systematically for regular silica based slurry as well as for slurry containing an organic biocide additive to prevent bacteria formation. The parameters examined were particle size distribution, zeta potential, bacteria count, total organic carbon concentration, silicon ion dissolution, material removal rate (MRR), and surface quality. The results indicated that aging influenced slurry performance negatively and even with the addition of biocide, organic contamination was observed at the extended aging periods. The material removal rates decreased significantly by aging and more surface deformations were observed on the wafer surfaces polished with the slurries destabilized with the elapsed time. Slurries containing biocide were detected to be more prone to agglomeration and increase in particle size as the time passes after the slurry is exposed to the environment. Furthermore, the impact of short time slurry aging (conditioning) on particle properties of the slurries containing polymeric additives and the adverse affects of extreme stability in the slurries containing surfactants are also discussed in terms of the two other factors that can cause variability in CMP slurry performance.Conference paperPublication Metadata only Surface characterization driven CMP optimization for gallium nitride(ECS, 2016) Karagöz, Ayşe; Siebert, M.; Leunissen, P.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, AyşeGallium nitride is a hard and chemically inert material demoting high material removal rates in the chemical mechanical planarization (CMP) applications. This paper focuses on the optimization of the process conditions to enhance material removal rates while controlling surface defectivity for GaN CMP. Two different crystallographic orientations of the GaN are characterized and compared to a commercial 2” GaN wafer to optimize the CMP performance on the basis of the wafer crystallographic nature, surface charge and topography. Slurry pH, the type of polishing pad and applied conditioning were evaluated to increase material removal rates of GaN while minimizing defect formation and enhancing the selectivity against silica.ArticlePublication Metadata only Characterization and antibacterial properties of nanoboron powders and nanoboron powder coated textiles(Elsevier, 2017-02) Akbar, Wazir; Noor, M. R.; Kowal, K.; Syed, T.; Soulimane, T.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Akbar, WazirThe antibacterial properties of boron-containing compounds are well known although there are limited studies available on the pure boron nanoparticles. In this paper, nanoboron particles are characterized in terms of their particle size, shape, stability and surface charge before and after their application onto textile surfaces to study their impact on bacterial activity. It was observed that the boron nanoparticles are effective in limiting the bacterial growth of both Gram-negative and positive species without requiring any stimulation to initiate the antibacterial action. In addition to the antibacterial functionality evaluation of the free boron nanoparticles, nanoboron coated textiles were also characterized and determined to change the wettability and surface charge of the textiles with a variable antimicrobial response to the different species. Consequently, we propose pure nanoboron as a new anti-bacterial agent that can function without external stimulation.Conference paperPublication Metadata only A modeling study on the layout impact of with-in-die thickness range for STI CMP(ECS, 2013) Kıncal, S.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharChemical Mechanical Planarization process has a proven track record as an effective method for planarizing the wafer surface at multiple points of the semiconductor manufacturing flow. One of the most challenging aspects of the CMP process, particularly in applications like Shallow Trench Isolation (STI), is the difference in relative removal rates of the different materials that are being polished. A certain amount of over-polish is required to clear oxide on top of the nitride, however, this over-polish may also lead to significant problems like dishing and erosion (introducing additional topography after the film has been planarized). This work formulates a methodology to predict how this additional topography is modulated by incoming layout properties introducing a parameter to accurately characterize line and space width on a layout with random geometric shapes.ArticlePublication Metadata only Tailoring silica nanotribology for CMP slurry optimization: Ca2+ cation competition in C12TAB mediated lubrication(ACS, 2010-04-12) Vakarelski, I. U.; Brown, S. C.; Başım, Gül Bahar; Rabinovich, Y. I.; Moudgil, B. M.; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharSelf-assembled surfactant structures at the solid/liquid interface have been shown to act as nanoparticulate dispersants and are capable of providing a highly effective, self-healing boundary lubrication layer in aqueous environments. However, in some cases in particular, chemical mechanical planarization (CMP) applications the lubrication imparted by self-assembled surfactant dispersants can be too strong, resulting in undesirably low levels of wear or friction disabling material removal. In the present investigation, the influence of calcium cation (Ca2+) addition on dodecyl trimethylammonium bromide (C12TAB) mediated lubrication of silica surfaces is examined via normal and lateral atomic force microscopy (AFM/LFM), benchtop polishing experiments and surface adsorption characterization methods. It is demonstrated that the introduction of competitively adsorbing cations that modulate the surfactant headgroup surface affinity can be used to tune friction and wear without compromising dispersion stability. These self-healing, reversible, and tunable tribological systems are expected to lead to the development of smart surfactant-based aqueous lubrication schemes, which include designer polishing slurries and devices that take advantage of pressure-gated friction response phenomena.ArticlePublication Metadata only Effect of different surface treatments on retention of cement-retained, implant-supported crowns(Quintessence Publishing Co. Inc., 2023) Ozyetim, E. B.; Özdemir, Zeynep; Başım, Gül Bahar; Bayraktar, G.; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, ZeynepTo evaluate the effect of different treatments applied to titanium implant abutment surfaces on the retention of implant-supported crowns retained using resin cement. Materials and Methods: A total of 72 titanium implant abutments were divided into six groups (n = 12 each) based on the selected surface treatment: (1) untreated; (2) sandblasted; (3) hydrogen peroxide–etched; (4) atmospheric plasma; (5) chemical mechanical polishing; and (6) titanium dioxide nanocoating. After the surface treatments, scanning electron microscopy analyses and roughness measurements of the abutment surfaces were performed. Then, 72 metal copings were fabricated and cemented onto the abutments with dual-curing resin cement. After the thermocycling process, crown retention was measured by using a universal testing machine. The experimental results were statistically evaluated with one-way analysis of variance, Tukey honest significant difference, and Tamhane T2 tests. Results: The highest surface roughness values were obtained in the sandblasted group (1.44 um), which also showed in the highest retention values (828.5 N), followed by the hydrogen peroxide etching group (490.7 N), the atmospheric plasma group (466.5 N), the chemical mechanical polishing group (410.8 N), and the control group (382.6 N). Conclusion: Sandblasting, hydrogen peroxide, etching, and atmospheric plasma treatments significantly increased crown retention, and all alternative treatments, with the exception of TiO2 nanocoating, worked better than the control samples.Conference paperPublication Metadata only Evaluation of infection resistance of biological implants through CMP based micro-patterning(Cambridge University Press, 2012-01) Başım, Gül Bahar; Özdemir, Zeynep; Karagöz, Ayşe; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep; Karagöz, AyşeBiomaterials 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.Conference paperPublication Metadata only Metal CMP optimization based on chemically formed thin film analysis(The Electrochemical Society, 2009) Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharThe conventional demands for development in semiconductor industry are changing as the Moore's Law is approaching to its limits. This paper demonstrates a theoretical optimization approach for the planarization of metal films by Chemical Mechanical Polishing (CMP) process. Optimal removal rate and a smooth surface finish post CMP can be achieved by the combined effect of the chemical and mechanical components of the process. Metal CMP necessitates a protective oxide film formation in the presence of surface active agents, corrosives, pH regulators etc' to achieve global planarization. Formation and mechanical properties of the chemically modified films determine the stresses develop in the film structure delineating the stability 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 which is expected to deal with atomic level structures.ArticlePublication Metadata only Application of chemical mechanical polishing process on titanium based implants(Elsevier, 2016-11-01) Özdemir, Zeynep; Ozdemir, A.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, ZeynepModification of the implantable biomaterial surfaces is known to improve the biocompatibility of metallic implants. Particularly, treatments such as etching, sand-blasting or laser treatment are commonly studied to understand the impact of nano/micro roughness on cell attachment. Although, the currently utilized surface modification techniques are known to improve the amount of cell attachment, it is critical to control the level of attachment due to the fact that promotion of bioactivity is needed for prosthetic implants while the cardiac valves, which are also made of titanium, need demotion of cells attachment to be able to function. In this study, a new alternative is proposed to treat the implantable titanium surfaces by chemical mechanical polishing (CMP) technique. It is demonstrated that the application of CMP on the titanium surface helps in modifying the surface roughness of the implant in a controlled manner (inducing nano-scale smoothness or controlled nano/micro roughness). Simultaneously, it is observed that the application of CMP limits the bacteria growth by forming a protective thin surface oxide layer on titanium implants. It is further shown that there is an optimal level of surface roughness where the cell attachment reaches a maximum and the level of roughness is controllable through CMP.