Applications of Scanning Probe Methods in Chemical Mechanical Planarization

This chapter describes scanning probe methods (SPM) used in chemical mechanical planarization (CMP). The term “planarization” refers to the reduction in step height present on a surface. Planarization is a key step in the fabrication process of an integrated circuit (IC) on silicon wafers, which allows the construction of multilevel interconnect structures. To precisely characterize the surface morphology, including step height, SPM are especially useful because fabricated patterns on wafers are complicated and have dimensions down to the micrometer/nanometer scale. The topographic information obtained can be used for the improvement of CMP processes, such as the optimization of CMP slurry formulation and polishing conditions. SPM are also found to be beneficial for investigating the surface properties of ICwafers. The electrical, dynamic-mechanical and tribological properties can be characterized using their multifunctional capabilities. For readers not familiar with CMP, the CMP process and its associated need for SPM are first outlined. Next, the two main SPM used in CMP, atomic force profilometry (AFP) and atomic force microscopy (AFM), are introduced and some representative data are presented for the characterization of line profile and surface roughness. Finally, techniques for understanding fundamental aspects of CMP mechanisms are discussed. The study of adhesion, friction, abrasion and associated material removal using an abrasive particle mounted on an atomic force microscope tip is presented to simulate microscale/nanoscale CMP processes. SPM provide insight into the microscopic CMP mechanisms to interpret the macroscopic CMP phenomena. Other related techniques, such as AFM phase imaging and scanning Kelvin probe microscopy (KPM) are also highlighted. SPM have made critical contributions to the development of CMP processes. The further improvement of SPM will significantly enhance the understanding and development of CMP technology.