Interfacial Force Analysis and Lubrication Behavior During Post-CMP Cleaning

This research investigates the tribological interactions in removal of nano-sized particles during post chemical-mechanical polishing (CMP) cleaning. Possible surface interactive forces are discussed in order to understand the particle adhesion and subsequent removal through physical and mechanical interactions. The investigation was carried out using theoretical analysis combined with experimental study. The theoretical analysis was based on the particle adhesion and removal. Surface interaction consideration includes brush load, frictional force, and hydrodynamic drag. Finite element modeling using ABAQUS was used. The polishing experiments were done on silicon wafers with SiO₂ slurry. Cleaning tests were done using DI water to brush clean the adhered particles from hydrophilic silicon surface. An Atomic Force Microscope (AFM) was used to evaluate the effective cleaning topography. It was found that particles are removed through sliding and rolling. The fluid film behavior was successfully illustrated using a modified Stribeck behavior with considering of changing material properties. New particle removal mechanisms and lubrication model were proposed.