Burak Ozdoganlar

An Investigation of the Influence of Orientation on CMP through Nanoscratch Testing

With the increase in integrated circuit (IC) feature density, the quality of chemical mechanical polishing (CMP) becomes more important as the copper interconnects decrease in size. The optimization of the IC manufacturing process will be greatly enhanced if the nanoscale effects on CMP are better understood. CMP-related wear at the sub-micron scale, where a single particle affects the microstructure of individual copper features within the substrate, needs to be investigated to account for wafer-scale variations. Hardness is known to affect the material removal rate, but the grain level mechanism of the removal process is not yet well known. In this work, the orientation-dependence of wear has been investigated by performing nanoscale scratch tests on single crystal copper along different crystallographic planes, indentified using orientation imaging microscopy (OIM). An analysis of the surface forces and post-scratch topography produced during the scratch tests was conducted and the results have been interpreted from a CMP perspective. Ultimately, these results are expected to refine existing material removal rate models which do not consider the sensitivity of microstructure on the CMP process.

THE EFFECT OF MICROSTRUCTURE ON CHEMICAL MECHANICAL POLISHING PROCESS OF THIN-FILM METALS

Chemical mechanical polishing (CMP) is a critical nanomanufacturing process used to remove or planarize ultrathin metallic, dielectric, or barrier layers on silicon wafers. The CMP process is a vital interim fabrication step for integrated circuits and data storage devices. One of the major shortcomings of existing CMP models is that they do not account for crystallographic effects of the thin film metal materials when predicting material removal rates. This work investigates the effect of the microstructure on the CMP of copper and metal thin films on silicon wafer. Nanoindentation tests were conducted to measure the hardness variations across a wafer surface due to the crystallography of the metal films. Spatial variation of mechanical properties was also input into an existing multi-scale CMP model. Nano-characterization and CMP experimental results are presented and compared to an existing CMP wear model.Copyright

On the Repetitive Impact Dynamics of One and Two Degree of Freedom Systems

Repetitive collision occurring between structural and machine components is a topic of practical and scientific importance. Some types of machinery are inherently susceptible to impacts because of the small clearances present between adjacent components, thermal expansion, and relative motion as in gear trains. One can observe repetitive impacts in milling machines, shakers and off-shore structures. Energy transfer between components that are subjected to repetitive impacts is a complex phenomenon that often exhibits deceptive and non-intuitive behavior. Even in seemingly simple structures, period-doubling bifurcations, sub-harmonic resonances, and chaotic responses occur. This paper presents detailed experimental data obtained from an impact vibration test stand that was instrumented for displacement, velocity, and impact force measurements. In addition, the apparatus was fabricated in such a way to allow for precise positioning of the impact point, and varying of the gap distance between impacting components. The paper includes companion simulation results obtained from a model for the repetitive impact dynamics of otherwise linear single or multiple degree of freedom discrete structures. Simulation results are presented for the effect of natural frequency placement, model dimension, and gap clearance on the qualitative and quantitative character of the response. Of particular interest is the transition of behavior as the system’s model is augmented from having one to several degrees of freedom.© 2005 ASME

Modeling and Measurement of Temperature Distributions in Bone Drilling

The heat generated during bone drilling can cause significant thermal damage to the tissue. Hence, prediction of the developing temperature field as a function of the drilling parameters is of high clinical value. However, no experimentally validated model has been reported yet. Furthermore, prior theoretical studies are limited to the drilling process, while extending the analysis beyond drill-bit retraction may be of equal interest. Therefore, the current study aims at experimental validation of a recently published thermal model for temperature distributions both during bone drilling, which is now expanded beyond drill-bit retraction. For validation of the model, a set of experiments was conducted on bovine cortical bone, following the new procedures suggested in the previous study in order to ensure a high degree of accuracy and repeatability. This study is based on thermal data collected at a distance range of 0.15 mm to 0.5 mm from the drilled hole, using thermocouples. Measuring temperatures closer to the drilled hole enabled better understanding of temperature distributions in the tissue in bone drilling. Comparison of experimental data and theoretical simulation results validate the model used. Additionally, about 57°C of difference of the maximum temperatures measured at the radii locations between 0.15 mm and 0.5 mm was observed.Copyright

Three-Dimensional Endmill Dynamics: Modal Development and Experimental Validation

In this paper the three-dimensional dynamic behavior of macro-scale milling tools is modeled using the spectral-Tchebychev technique while considering the actual fluted cross-sectional geometry and pretwisted shape of the tools. The bending and torsional behavior of three different fluted endmills is compared to finite element predictions and experimental results obtained using impact testing with free-free boundary conditions. The percent difference between experiment and the spectral-Tchebychev method predictions is shown to be 3% or less for all three tools while considering the first six bending modes and first two torsional modes. For the same modes, the spectral-Tchebychev and finite element model predictions agreed to better than 1%.© 2011 ASME