Tribology and Removal Rate Characteristics of Abrasive-Free Slurries for Copper CMP Applications

This study employs real-time high-frequency frictional force analysis coupled with removal rate studies to quantify the extent of frictional forces encountered during copper polish using abrasive-free slurries and to establish the time-dependent tribological attributes of the process. The study also uses spectral analysis of the frictional force data to validate and explore the subtle characteristics of the formation and extinction of the copper complex layer known to play an integral role in abrasive-free copper chemical mechanical planarization (CMP). It was found that copper removal rates are at least partially driven by coefficient of friction, which is similar to the case of interlayer dielectric (ILD) CMP. Spectral analysis suggests that the periodicity of the copper complex layer formation and abrasion is approximately 10ms.