Advanced Slurry Formulations for New Generation Chemical Mechanical Planarization (CMP) Applications
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Advanced Slurry Formulations for New Generation Chemical Mechanical Planarization (CMP) Applications Bahar Basim1 and Ayse Karagoz1,2, Zeynep Ozdemir1 1 Ozyegin University, Faculty of Engineering, Mechanical Engineering Department, Alemdag, Istanbul, Turkey 2 Yildiz Technical Universityy, Faculty of Chemistry & Metallurgy, Bioengineering Department, Davutpasa, Istanbul, Turkey ABSTRACT 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. INTRODUCTION Microelectronic circuit densities have increased about a hundred fold in last twenty years. Chemical Mechanical Planazition process evolved with the advances in microelectronics to ensure planarity for metal and dielectric films to build multi layer metallization (MLM). Many studies have been conducted to characterize CMP experimentally and through modeling to control critical polishing parameters on metals like tungten and copper as well as dilectrics like silica in addition to the new generation materials like germanium and gallium arsenide [1]. Tungsten has been the metal of choice to fill in the vias starting with the aliminum metallization and remained to be the first layer fill metal for plugs even for the copper metallization. Therefore, it is one of the best studied metal films for the CMP applications and hence it is selected for the primary analyses in this study. Metals tend to form native oxides when they are exposed to oxidizing environments which maybe a self-protective layer in some cases. The self-protective nature of the metal oxide thin films are determined by Pilling-Bethworth ratio (P-B Ratio) in air, which compares the molar volume of the oxide film formed to the molar volume of its native metal as shown in Equation 1, [1]
where, Ao is the molecular o
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