The Role of Ce3+ vs. Ce4+ during the Polishing of Silicon Dioxide and Silicon Nitride Films using Ceria Abrasives

Abstract

Removal rate mechanisms of silicon dioxide and silicon nitride films during chemical mechanical polishing using ceria particles-based dispersion in the presence and absence of different additives are discussed. Our results show that ceria particles give high silicon dioxide and silicon nitride removal rates due to the reactivity of the Ce 3+ species with silicon dioxide or the sub-oxide formed on the silicon nitride surface by hydrolysis. With several additives, complete blockage of the reactive species and the reduction of oxide and nitride removal rates to <2 nm/min occur when the amount of the additive adsorbed has reached a limiting value. Silicon nitride removal rates can also be suppressed to <2 nm/min when the conversion of the nitride surface to suboxide is hindered due to the adsorption of additives on the nitride surface.

Evaluation of a Photosensitizer Redox Couple for Oxide Removal Rate Tunability in Shallow Trench Isolation Chemical Mechanical Planarization

“…Therefore, significant work has focused on increasing the O vac concentration (i.e., Ce 3+ state) on the CeO 2 surface by incorporating various rate enhancing additives to increase oxide MRR. [12][13][14][15][16] Kim et al showed that the use of Ce 3+ enriched core-shell CeO 2 nanoparticles allowed for increased MRR in comparison to that of pristine CeO 2 . 12 Doi et al also showed an increase in MRR as a function of Ce 3+ concentration in which picolinic acid was used as a rate enhancer.…”