Chemical mechanical planarization of copper using transition alumina nanoparticles

Nanoscale transition alumina with primary size of 20 nm was prepared via wet milling of a boehmite feed calcined at 500 °C for 2 h. The transition alumina was composed of a crystallized gamma phase and an amorphous component, and showed a high surface area of 221 m2/g and substantially low density of 2.56 g/cm3. The amount of hydrated alumina was revealed by thermogravimetric analysis and X-ray diffraction analyses. Aqueous slurries made from the freeze dried and redispersed transition alumina abrasives demonstrated superior surface finish on tantalum (Ta) and thermal oxide wafers along with a material removal rate of copper layer up to 2700 Å/min in copper chemical mechanical planarization.