Mechanical and tribological properties of interlayer films for the damascene-Cu chemical-mechanical planarization process

Abstract

Chemical-mechanical planarization (CMP) has emerged as the most preferred method to achieve excellent global and local planarity in the damascene-Cu process. As the feature sizes shrink, understanding the fundamentals of CMP is critical for successful implementation of the CMP process in sub 0.35-µm technology. It is also important to understand the effects of mechanical and tribological properties of the interlayer films on the CMP process to conduct successful evaluation and implementation of these materials. In this paper, we present the mechanical and tribological properties of various interlayer films (SiO2, SiC, low-k B, low-k C, Ta, and Cu) and discuss the CMP process of the films in an alumina-based Cu slurry. Mechanical properties were evaluated using a nanoindentation technique. A micro-CMP tester was used to study the fundamental aspects of the CMP process. The coefficient of friction (COF) was measured during the process and was found to decrease both with downward pressure and with platen rotation. An acoustic sensor, attached to the substrate carrier, was used to monitor the process, and the signal was recorded to examine the difference in polishing behavior of these films. The acoustic emission (AE) signal was found to increase with the increase in platen velocity and pressure. Effects of machine parameters on the polishing behavior of the interlayer films and the correlation of mechanical properties with tribological properties have been discussed.