Pad Surface Treatment to Control Performance of Chemical Mechanical Planarization

Abstract

The polishing pad plays a key role in chemical mechanical polishing. Abrasive particles are held on the polishing pad. The work piece surface is polished when the abrasive particles are pressed against the surface by pad asperity. A significant feature of the pad is its surface asperities. Pad asperities have different amplitudes and frequency components. A small amplitude and high-frequency components will result in roughness, whereas a large amplitude and low-frequency components will result in waviness of pad. The conventional polishing pad is a polymer sheet that has asperities and viscoelasticity; thus pressure under the wafer is unevenly distributed because of the asperities on pad surface. In this research, we chose the mechanical treatment method for controlling the asperities. The buffing process is one method of mechanical surface treatment. In the buffing process, changed roughness affects the physical properties of pad such as viscoelasticity, compressibility, recovery, deformation amount, wettability. The purpose of the buffing process is to control the polishing performance of pad by controlling pad waviness and roughness. In this research, urethane pad for chemical mechanical planarization is studied. Results show that the pad profile affects the stability of the polishing process and break-in process, whereas the removal rate of wafer depends on the pad surface roughness. We found that the mechanical surface treatment of the pad is useful for controlling the polishing performance.