Study of interfacial interaction during chemical mechanical polishing (CMP) of dielectric silicon dioxide

Chemical mechanical polishing (CMP) is an advanced technology utilized to achieve local and global planarization through synergistic interactions of both mechanical abrasion by abrasive particles and chemical reaction via chemical additives. The CMP process has played an important role in the microelectronic device fabrication industry. The introduction of CMP to microelectronic fabrication processes enables multilevel interconnections, yielding high packing densities, the density of transistors per square millimeter of silicon. The high packing density is responsible for the high-speeds achieved by semiconductor devices.; As interconnection dimensions shrink and the number of metal layers grows in multilevel interconnects, the need for CMP increases. In spite of the growth in the role of the CMP process in microelectronic device fabrication, the principles and mechanisms of polishing have not been clearly understood. The clear delineation of polishing phenomena assist in further optimization of the CMP process.; The CMP is the result of interfacial interactions at the pad-particles-wafer interface. Real-time observations of the interfacial interaction are essential in understanding polishing principles and mechanisms. This study details observations and gives analysis of interfacial interactions in order to delineate polishing mechanisms.; The variation in friction force has been investigated via in situ friction force measurement. Based on the friction force arising from the pad-wafer interface or pad-particles-wafer interface, the contact variation at the interface was delineated. The contact variation was analyzed using a contact model developed from the principles of friction force and micro-contact mechanics.; Slurry properties such as pH, particle size, and solids loading are important factors in determining polishing rate. The effect of pH, particle size, and solids loading of colloidal silica slurry on polishing performance such as polishing rate, surface finish was investigated to validate polishing mechanism performed by colloidal silica slurry; we verified that the polishing rate and surface finish were significantly dependent on the dynamic motions such as rolling or sliding of particles, interaction force between two surfaces, contact area, and indentation depth of particles into the wafer surface.