Faculty of Engineering

Permanent URI for this communityhttps://hdl.handle.net/10679/10

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3-D extension of chemical mechanical polishing for nano-structuring applications on alternative technologies
(The Electrochemical Society, 2016) Özdemir, Zeynep; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep
In this study we tune the chemical mechanical polishing process to a 3-D level to generate controlled nanostructures on functional metallic surfaces such as titanium implants and steel based heating elements. The chemical passivation action of the CMP process on metallic surfaces enables the formation of inert interfaces resistant to corrosion and degradation while the induced nanostructures help tune the surface attachment/detachment ability as these surfaces interact with alternative external elements.
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An active brace for controlled transdermal drug delivery for adjustable physical therapy
(IEEE, 2014) Erol, Levent; Bebek, Özkan; Karagöz, Ayşe; Başım, Gül Bahar; Mechanical Engineering; BEBEK, Özkan; BAŞIM DOĞAN, Gül Bahar; Erol, Levent; Karagöz, Ayşe
This study presents an active brace which is a cost efficient precision-controlled advanced therapy medicinal product for time and rate controlled transdermal drug delivery (TDD) through the use of drug containing nanoparticles and electronics. The active brace is designed to adjust the pressure at the contact area where the medication is applied. The drug is contained in the nanoparticles produced and takes effect when the nanoparticles burst under pressure. The brace is designed to be compact and wearable which can be preprogrammed by a specialist to continue treatment sessions outside the medical facilities providing convenience and comfort to the patient.
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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, Zeynep
Chemical 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.
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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, Zeynep
Modification 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.
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Biomaterials applications of chemical mechanical polishing
(IEEE, 2012) Başım, Gül Bahar; Özdemir, Zeynep; Mutlu, Ö.; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep
Chemical Mechanical Polishing (CMP) is used in semiconductor industry to enable planarization of the interlayer dielectrics and metals. In this study, CMP is used as a polishing technique to modify the surface roughness of the bio-implant materials in a controlled manner. As an alternative technique to sand-blasting/etching or laser structuring on the implant surfaces, CMP results in formation of a protective oxide layer on the titanium surfaces that can limit surface contamination while enabling surface nano-structuring that is known to promote bioactivity. Keywords: CMP, Titanium Implants, Biomaterials, Micro-Patterning.
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A Cahn-Hilliard modeling of metal oxide thin films for advanced CMP applications
(ECS, 2014) Karagöz, Ayşe; Şengül, Yasemin; Başım, Gül Bahar; Natural and Mathematical Sciences; Mechanical Engineering; ŞENGÜL, Yasemin; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe
Chemical mechanical planarization (CMP) process enables topographic selectivity through formation of a protective oxide thin film on the recessed locations of the deposited metal layer, while a continuous chemical oxidation reaction is followed by mechanical abrasion takes place on the protruding locations. This paper demonstrates a new approach to CMP process optimization in terms of analyzing the nano-scale surface topography of the protective metal oxide films and modeling their growth through a Cahn-Hilliard equation (CHE) approach as an alternative to classical nucleation theory. It is observed that the material removal rate mechanisms and the consequent planarization performance depend on the nature of nucleation of the metal oxide films, which is a function of the oxidizer concentration of the CMP slurry.
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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, Wazir
The 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.
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Characterization of chemically modified thin films for optimization of metal CMP applications?
(Cambridge University Press, 2013) Başım, Gül Bahar; Karagöz, Ayşe; Özdemir, Zeynep; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe; Özdemir, Zeynep
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.
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Characterization of nano-scale protective oxide films: application on metal chemical mechanical planarization
(The Electrochemical Society, 2015) Karagöz, Ayşe; Craciun, V.; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe
This study focuses on the characterization of nano-scale metal oxide films for chemical mechanical planarization (CMP) applications. The protective nature of the self-grown metal oxide layers in the CMP slurry environment enable topographic selectivity required for metallization of interconnects. Tungsten was selected as the model metal film to study the formation and characteristics of the metal oxide nano-layers since tungsten CMP is very well-established in conventional semiconductor manufacturing. The tungsten oxide nano-films were characterized for thickness, density and surface topography in addition to evaluation of their protective nature by calculation of the Pilling-Bedworth (P-B) ratios. It was observed that in addition to controlling the self-protective characteristics, the oxidizer concentration also affects the surface structure of the metal oxide films resulting in significant changes in the CMP process performance in terms of material removal rates and surface finish with a sweet-spot detected at 0.075 M H2O2 concentration.
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Chemical mechanical planarization studies on gallium nitride for improved performance
(IEEE, 2015) Karagöz, Ayşe; Başım, Gül Bahar; Siebert, M.; Leunissen, L. A. H.; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe
In this study, a systematic experimental approach has been followed to determine the conditions to promote material removal rate while controlling surface defectivity for GaN CMP. Silica based slurries were used to optimize the CMP conditions for a commercial GaN sample as a function of pH, and type of polishing pad and conditioning. In addition, CMP responses of Face A and Face B type crystallographic GaN surfaces were evaluated and compared to the 2" GaN wafer with unknown surface crystallographic structure. It is observed that the contact angle responses of the different crystallographic surfaces can help identify the type of GaN surface and support predicting the CMP performance simultaneously.
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Chemical mechanical polishing implementation on dental implants
(IEEE, 2015) Başım, Gül Bahar; Özdemir, Zeynep; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep
In this study, chemical mechanical polishing (CMP) technique is introduced as a new alternative to generate controlled nano/micro scale roughness on the titanium implant surfaces. It is known that micro scale patterns induced on biomaterial surfaces promote bio-compatibility by increasing the capability of cell attachment. However, current developments on biomaterials highlight the impact of nano-scale roughness in promoting the biocompatibility on the metallic implant surfaces. CMP process brings the advantage of inducing smoothness or controlled nano-structures on the bio-implant material surfaces. Here, we focus particularly on the dental implant applications to change the surface roughness and the resulting bioactivity in a controlled manner.
Open Access
Controlling germanium CMP selectivity through slurry mediation by surface active agents
(The Electrochemical Society, 2015-08-10) Karagöz, Ayşe; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe
New developments and device performance requirements in microelectronics industry add to the challenges in chemical mechanical planarization (CMP) process. One of the recently introduced materials to semiconductor manufacturing is germanium which enables improved device performance through better channel mobility in shallow trench isolation (STI) applications for advanced circuits. This paper focuses on controlling germanium/silica selectivity for advanced STI CMP applications through slurry modification by surface active agents. Surface adsorption characteristics of cationic and anionic surfactants on germanium and silica wafers are analyzed in order to control selectivity as well as the defectivity performance of the CMP applications. The effects of surfactant charge and concentration (up to self-assembly) are studied in terms of slurry stability, material removal rates and surface defectivity. Surface charge manipulation by the surfactant adsorption on the germanium surface is presented as the main criteria on the selection of the proper surfactant/oxidizer systems for CMP. The outlined correlations are systematically presented to highlight slurry modification criteria for the desired selectivity results. Consequently, the paper evaluates the slurry selectivity control and improvement criteria for the new materials introduced to microelectronics applications with CMP requirement by evaluating the germanium silica system as a model application.
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Development of 3-D chemical mechanical polishing process for nanostructuring of bioimplant surfaces
(ECS, 2014) Özdemir, Zeynep; Orhan, Orçun; Bebek, Özkan; Başım, Gül Bahar; Mechanical Engineering; BEBEK, Özkan; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep; Orhan, Orçun
This study focuses on the development of a three dimensional chemical mechanical polishing (CMP) process to induce smoothness or controlled nano-roughness on the bio-implant material surfaces, particularly for an application on the dental implants. CMP helps produce implant surfaces that are cleaned from potentially contaminated surface layers by removing a nano-scale top layer while simultaneously creating a protective oxide film on the surface to limit any further contamination to minimize risk of infection. Hence, we propose CMP as a synergistic method of nano-structuring on the implant surfaces and focus on extending the process to a 3-D platform to implement it on the dental implants.
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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, Zeynep
Bioactivity 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).
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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, Zeynep
To 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.
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Effect of slurry aging on stability and performance of chemical mechanical planarization process
(Elsevier, 2011-03) Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar
Chemical 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.
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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, Ayşe
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.
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, Rawana
Chemical 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.
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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 Bahar
Chemical 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.
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Improving selectivity on germanium CMP applications
(ECS, 2014) Karagöz, Ayşe; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Karagöz, Ayşe
In the presented paper, the adsorption characteristics of cationic and anionic surfactants on germanium and silica were studied in order to improve selectivity in germanium based shallow trench isolation chemical mechanical planarization applications. It was observed that the very strong or loose self-assembled surfactant structures can help obtain selectivity on the silica/germanium systems. Simultaneously, good defectivity control with a sufficient material removal rate was obtained. The surface charges manipulated by the surfactant adsorption and the hydrophobic nature of the germanium surface were main criteria on the selection of the proper surfactant/oxidizer system. In addition, impact of surfactant addition on particle-particle interactions controlling slurry stability was also investigated in the paper.

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