Probing the Effect of Point of Use Filtration on Cu CMP Slurry Health

Abstract

Chemical mechanical planarization (CMP) is a process that balances chemical surface modification and mechanical removal utilizing a nanoparticle dispersion (slurry) to limit defects and irregularities on the wafer surface. Implementing point of use (POU) filtration prior to the CMP process is crucial in capturing rogue particle aggregates that are known to induce defects such as scratching and pitting. As technology continues to advance CMP slurries are increasing in complexity, making it necessary to unravel the dynamic synergy between the formulated slurry and filtration media. More specifically, this work set out to investigate the non-covalent interactions such as hydrogen bonding, pi interactions, or dispersion forces that occur at the interface of a fundamental Cu CMP slurry and a polyamide and polypropylene based media. The slurry utilized in this study contained SiO2 abrasive particles due to its selectivity for Cu, glycine as a complexing agent, benzotriazole (BTA) as a passivating agent, H2O2 as an oxidizing agent, and pH adjusters. It has been known that Cu-glycine complexes increase the hydroxyl radical concentration, which in turn enhances the MRR. Initial results revealed that there was a subtle difference in the MRR post-filtration independent of the media used, meaning that both filters were capable of interacting with the chemistry in the slurry during the filtration process. In order to determine what chemistry was being removed through adsorption the following techniques were employed as a function of the filtration process, dynamic light scattering (DLS), zeta potential, electrochemical quartz crystal nanobalance (EQCN), UV-Vis spectroscopy, potentiodynamic scan analysis, and measuring Cu removal rate. Ultimately, results show that both polymeric media, despite the difference in their characteristics (backbone structure, hydrophilicity, and pore size) were not only effective in removing large particle aggregates but were able to alter the slurry integrity by removing key complexing chemistry, which significantly impacts the Cu film formation and removal processes.