Investigation of slurry systems in metal and dielectric chemical mechanical polishing

The properties of slurries play a significant role in chemical mechanical polishing (CMP) of metal and dielectric films in semiconductor device manufacturing. This study investigates the effects of the size, shape, and hardness of uniform abrasive particles of simple and composite natures on the polishing of copper, tantalum, and thermal oxide films in the presence of different chemical reagents.; It was shown that the total surface area of the solids in the slurry controlled the material removal rate by pure silica for both Cu and Ta, while the surface quality of the polished films was better when using higher silica contents. Ceria particles are the choice abrasives in polishing of oxide surfaces. Since it is difficult to prepare in quantities uniform ceria particles of various shapes, the latter were prepared by using monodispersed cubic and ellipsoidal hematite (Fe2O3) particles and spherical silica, and coating them with nanosized ceria. The polishing data were then obtained using slurries of all these particles and the results were compared with slurries containing only nanosized ceria. At the same pH and the same solid content, the removal rates of these slurries followed the contact area model. Furthermore, slurries containing mixtures of particles performed more efficiently than those of individual particles.; Interactions of abrasive particles with surface films to be polished are also very important in CMP. In this study, the packed column technique was employed to investigate the physical and chemical reactions at the particle/film interfaces under conditions that simulate CMP processes. Well-defined dispersions of uniform particles, including spherical silica, calcined alumina, and silica cores coated with nanosized ceria particles were used to evaluate particle adhesion on copper and glass beads. It was shown that pH and the slurry flow rate had significant effects on particle deposition and detachment. The attachment results of silica particles on copper beads in the presence of H2O 2 of various concentrations at pH 4 correlated well with the removal rates of copper films. In contrast, the detachment results of alumina particles from copper beads at different pH values without peroxide showed the same trend as the removal rate of Cu films.; The packed column technique was also employed to evaluate the effects of added chemicals in the slurries. Thus, green precipitates were observed on ageing the effluent at room temperature, after glycine-peroxide solutions were passed through the column packed with copper beads. In a series of experiments, several parameters were systematically varied to elucidate the effects responsible for the precipitate formation and to correlate to the defects observed in CMP process using glycine-peroxide based slurries. In order to improve the Cu removal rate and surface quality after the polishing process, preliminary investigations of novel organic additives, including hydrophobic complexing agents, were also carried out. It was found that 1,10-phenanthroline acted efficiently in Cu CMP.