Person: BAŞIM DOĞAN, Gül Bahar
Loading...
Email Address
Birth Date
Name
Job Title
First Name
Gül Bahar
Last Name
BAŞIM DOĞAN
37 results
Publication Search Results
Now showing 1 - 10 of 37
ArticlePublication Metadata only Impact of pad conditioning on thickness profile control in chemical mechanical planarization(Springer Science+Business Media, 2013-01) Kincal, S.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharChemical mechanical planarization (CMP) has been proven to be the best method to achieve within-wafer and within-die uniformity for multilevel metallization. Decreasing device dimensions and increasing wafer sizes continuously demand better planarization, which necessitates better understanding of all the variables of the CMP process. A recently highlighted critical factor, pad conditioning, affects the pad surface profile and consequently the wafer profile; in addition, it reduces defects by refreshing the pad surface during polishing. This work demonstrates the changes in the postpolish wafer profile as a function of pad wear. It also introduces a wafer material removal rate profile model based on the locally relevant Preston equation by estimating the pad thickness profile as a function of polishing time. The result is a dynamic predictor of how the wafer removal rate profile shifts as the pad ages. The model helps fine-tune the pad conditioner operating characteristics without the requirement for costly and lengthy experiments. The accuracy of the model is demonstrated by experiments as well as data from a real production line. Both experimental data and simulations indicate that the smaller conditioning disk size and extended conditioning sweep range help improve the post-CMP wafer planarization. However, the defectivity tends to increase when the conditioning disk sweeps out of the pad radius; hence, the pad conditioning needs to be designed by considering the specific requirements of the CMP process conducted. The presented model predicts the process outcomes without requiring detailed experimentation.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.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 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.ArticlePublication Metadata only Effect of chemical mechanical polishing on surface nature of titanium implants FT-IR and wettability data of titanium implants surface after chemical mechanical polishing implementation(Elsevier, 2017) Özdemir, Zeynep; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, ZeynepBioactivity of titanium depends on the quality and characteristics of its surface oxide film. Through implementation of chemical mechanical polishing (CMP) process on titanium plates, a protective oxide (titania) film grows on the titanium based implant surface. In this article, surface properties of the titanium oxide are investigated as a function of the CMP process conditions. Surface responses were evaluated in terms of wettability, nano-scale surface roughness and material removal rates (MRR). Surface chemical compositions were also evaluated through Fourier transform infrared spectroscopy (FT-IR).ArticlePublication Metadata only Metal oxide thin film characterization for new generation chemical mechanical planarization development(The Electrochemical Society, 2016) Başım, Gül Bahar; Karagöz, Ayşe; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, AyşeThis study targets to create a basis for the process development in the new generation semiconductor industry dealing with atomic scale devices. We focus on the CMP process development as it is used for the current and future semiconductor materials in microelectronics industry for metallic, semiconductor and dielectric materials. Particularly, formation and atomic level removal mechanisms of the CMP induced metal oxide thin films for metallic layers and chemically modified hydrated layer interaction for the semiconductor films are presented as a focus for the new generation device manufacturing.ArticlePublication Metadata only Particle size analysis on wide size distribution powders; effect of sampling and characterization technique(Elsevier, 2015-01) Başım, Gül Bahar; Khalili, M.; Mechanical Engineering; BAŞIM DOĞAN, Gül BaharParticle size distribution of powders plays a very important role in determining the critical chemical and physical properties of the particulate systems. Precise determination of particle size distribution depends on effective sampling of the powders, which is more pronounced for the particulate systems with a wide particle size distribution. Predominantly, the significant increase in the total surface area of the powders at nanometer scale particle sizes may lead to improper characterization of the bulk if the sampling technique fails to collect and represent them in the analyses. In this study, effects of sampling on the precision of particle size analysis are studied on a clay sample with a wide particle size distribution (particles ranging from nanometer to micrometer sizes) using light scattering technique in aqueous media. Three different sampling methods are applied to systematically analyze the effect of sampling on particle size measurements including; riffling the original sample into sixteen equal parts, sampling the powder after removing the very fine and very coarse size particles and riffling to sixteen parts and finally by riffling the powder to the exact feed amount of the particle size analyzer. The effectiveness of the applied methods were compared statistically by calculating the coefficient of variance (CV) values of the 10%, 50% and 90% passing particle size data of the sequential runs. The most effective sampling method was determined to be riffling the sample to the exact feed amount of the analyzer based on obtaining the minimum CV values of the measurements. In the second part of the study, results of size distribution analyses conducted by different particle size analyzers utilizing numerous characterization techniques are compared using the most effective sampling technique developed in the first part. It is observed that the use of different characterization equipment tend to result in variations in the particle size distributions of the same powder which presents another variability in classification of the wide particle size distribution powders.ArticlePublication Metadata only Optimized process and tool design for gan chemical mechanical planarization(The Electrochemical Society, 2017-10-04) Ozbek, S.; Akbar, Wazir; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Akbar, WazirIn this paper, we present a systematic approach to the gallium nitride (GaN) chemical mechanical planarization (CMP) process through evaluating the effect of crystallographic orientation, slurry chemistry and process variables on the removal rate and surface quality responses. A new CMP process and a complementary tool set-up are introduced to enhance GaN material removal rates. The key process variables are studied to set them at an optimal level, while a new slurry feed methodology is introduced in addition to a new tool set up to enable high material removal rates and acceptable surface quality through close control of the process chemistry. It is shown that the optimized settings can significantly improve the material removal rates as compared to the literature findings while simultaneously enabling a more sustainable process and potential removal selectivity against silica.ArticlePublication Open Access A fundamental approach to electrochemical analyses on chemically modified thin films for barrier CMP optimization(IOP Publishing, 2019-04-09) Yagan, Rawana; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Yagan, RawanaChemical Mechanical Planarization (CMP) process development for 10nm nodes and beyond demands a systematic understanding of atomic-scale chemical and mechanical surface interactions for the control of material removal, selectivity, and defectivity. Particularly the CMP of barrier/liner films is challenging with new materials introduced to better adhere the contact metal at the interface and limit the probability of metal diffusion to the transistors. The relative selectivity of the CMP removal rates of the barrier materials against the contact metal needs to be controlled depending on the integration scheme. This paper focuses on understanding the barrier CMP process selectivity on the model W/Ti/TiN applications through electrochemical evaluations and chemically modified thin film analyses. Ex-situ electrochemical evaluations are conducted on the W/Ti/TiN system to evaluate the passivation rates in various slurry formulations as a function of the slurry chemistry and the abrasive particle solids loading. Results of the passivation rates are compared to the removal rate selectivity and the post CMP surface quality on blanked W, Ti, and TiN films. A new methodology for CMP slurry formulations through ex-situ electrochemical analyses is outlined for new and more challenging barrier films while simultaneously highlighting an approach for corrosion prevention on the metallic layers.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.