Chemical mechanical polishing has long been adopted as a technique to enable global planarization for semiconductor applications.  The main functional requirements such as selectivity, enhanced material removal rates and minimal defectivity are achieved through advanced slurry formulations and process set up.  In this study we tune the CMP process to generate controlled nanostructures to benefit from the synergy it enables on metallic surfaces namely; (i) formation of a protective metal oxide film during polishing and (ii) ability to tune the root mean square surface roughness from nano to micro scale.

The first application is on titanium surfaces to modulate the surface structure of the implantable biomaterials.  We have demonstrated earlier that the CMP application on dental implants have improved the in-vitro biocompatibility with 3-D applications being developed [1].  The application we propose in this study is the application of the CMP induced nano-structuring for the lime-scale prevention on the heating elements. Lime scale formation by the hard water often causes numerous technical and economic problems in industrial and house-hold equipment. In scope of the work bare stainless steel and alternative coating materials were characterized for surface roughness, surface energy and wettability responses in order to observe the CMP induced nanostructure levels on the CaCO₃ attachment behavior. Surface topography was evaluated through atomic force microscopy (AFM) on all the materials after CMP process was conducted. Accelerated lime scale formation tests were performed on these surfaces and the affect of random nanostructures and their thermal expansion abilities as live nanostructures were evaluated on the exfoliation of the lime scale. From the experimental work surface total energy was observed to be one of the main indicators for the lime scale adhesion prevention [2].  Figure 1 shows the calcination removal performances of the alternative coating elements as compared to the steel after the heat cycle the heating elements are exposed to..                     

References

1. Ozdemir Z., Orhan O., Bebek O., Basim G. B., Development of 3-D Chemical Mechanical Polishing Process for Nanostructuring of Bioimplant Surfaces, ECS Transactions, 2014, 61, 21-26.
2. Basim G.B., Chemical Mechanical Polishing Induced Live Nano-Structures for Lime-Scale Prevention on Heating Elements. International Patent Office Application No: PCT/TR2013/000378, Application Date: 31.12.2013.