| The demand for smaller, faster devices has led the integrated circuit (IC) industry to continually increase the device density on a chip while simultaneously reducing feature dimensions. Copper interconnects and multilevel metallization (MLM) schemes were introduced to meet some of these challenges. With the employment of MLM in the ultra-large-scale-integrated (ULSI) circuit fabrication technology, repeated planarization of different surface layers with tolerance of a few nanometers is required. Presently, chemical-mechanical planarization (CMP) is the only technique that can meet this requirement. Damascene and shallow trench isolation processes are currently used in conjunction with CMP in the fabrication of multilevel copper interconnects and isolation of devices, respectively, for advanced logic and memory devices. These processes, at some stage, require simultaneous polishing of two different materials using a single slurry that offers high polish rates, high polish selectivity to one material over the other and good post-polish surface finish. Slurries containing one kind of abrasive particles do not meet most of these demands due mainly to the unique physical and chemical properties of each abrasive. However, if a composite particle is formed that takes the advantages of different abrasives while mitigating their disadvantages, the CMP performance of resulting abrasives would be compelling.; It is demonstrated that electrostatic interactions between ceria and silica particles at pH 4 can be used to produce composite particles with enhanced functionality. Zeta potential measurement and TEM images used for particle characterization show the presence of such composite particles with smaller shell particles attached onto larger core particles. Slurries containing ceria (core)/silica (shell) and silica (core)/ceria (shell) composite particles when used to polish metal and dielectric films, respectively, yield both enhanced metal and dielectric film removal rates and better post-polish surface roughness values compared to those containing single kind of particles. Several arguments are proposed to explain the enhanced CMP performance with the composite abrasives. The effect of surface charge of the composite abrasive and the hardness of the core particles in the composite abrasives contained in the polishing slurry on polish rates of different films is discussed.; Also, as a part of this thesis, several issues related to CMP were addressed. The planarization ability of Cu CMP slurry containing alumina coated silica particles was studied to elucidate the role of pattern geometry in affecting polish rate and also generating pattern dependent defects like dishing and erosion. Additionally, a polishing process was devised which, when viewed with the optical profilometer, eliminated surface defects including shallow and deep scratches and pits already present in a copper film. Also, molybdenum dioxide (MoO2) was evaluated as a potential abrasive for a highly reactive copper CMP slurry with potassium iodate as the oxidizing agent. Finally, the interaction of amino acid additives in ceria slurries with the silicon nitride film during STI CMP is discussed.; Directions for future work have been presented at the end of the thesis. |
