Effect of Slurry Temperature on Cu Chemical Mechanical Polishing with Different Oxidizing Agents
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Effect of Slurry Temperature on Cu Chemical Mechanical Polishing with Different Oxidizing Agents Subrahmanya Mudhivarthi1, 2 and Ashok Kumar1, 2 1
Department of Mechanical Engineering, Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, Florida-33620.
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ABSTRACT Chemical Mechanical Planarization (CMP) has evolved as one of the most critical and significant process in the manufacturing of semiconductor devices. Copper has become the material of choice for the interconnect wiring. The effect of heat generation at the interface is realized to be significant on copper CMP process. The increase in the oxidation rate of the chemical reaction and viscoelastic properties of polishing pads due to increase in temperature at the surface results in increased removal rates and change in planarization performance. In this research, the effect of temperature on the CMP performance using two most common oxidizing agents, KIO3 and H2O2 has been investigated using the CETRTM bench-top CMP tester. The coefficient of friction at the interface of polishing using both the oxidizers at different temperatures was monitored. The generated surface roughness post CMP was evaluated for samples polished using different oxidizing agents at different slurry temperatures. The AFM study was carried out using Digital InstrumentsTM D3100 instrument. This study is aimed at understanding the effect of temperature on the CMP process performance and the relative sensitivity of two most common oxidizers used in copper CMP towards temperature. INTRODUCTION Copper has replaced aluminum as an interconnect wiring material for the damascene structures to be used in ultra large scale integration of microelectronic devices. Copper has superior electromigration resistance and much lower resistivity when compared to Aluminum. As the device sizes shrink and the prominence of Multilevel Metallization structures increase, CMP process has evolved into a crucial process step during device fabrication [1, 2]. Copper CMP has gained prominence as the metal overburden is planarized and removed extensively to achieve damascene structure. Copper CMP process involves chemical modification of the soft copper surface followed by mechanical abrasion and subsequent dissolution of the removed copper debris into the slurry [3-5]. Process of reaction of copper with slurry has high activation energy of about 0.5 eV compared to approximately 0.06 eV activation energy of dielectric CMP process [6]. Thus, copper CMP process is estimated to be highly sensitive to the temperature. Heat is generated at the interface of polishing due to friction and interaction of the asperities of wafer, pad and the abrasive particles. Thus generated heat is transferred from the interface through conduction and convection heat transfer modes to wafer, polishing pad and to the slurry. Slurry acting as a cooling agent and thermally more conducting copper surface take majority of the heat generated at the interface. As a result, copper
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surface interact
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