Isolating inert regions and active pathways within an integrated circuit (IC) is facilitated through dielectric deposition of tetraethyl orthosilicate (TEOS) during shallow trench isolation (STI). Chemical mechanical planarization (CMP) is used to selectively target and remove the excess TEOS overburden with colloidal suspensions (slurries) containing ceria (CeO2) abrasives. Literature has shown that oxygen vacancies, indicating the presence of Ce3+ particles on the CeO2 surface, are an important factor in achieving high material removal rates. A fundamental drawback of the reactive nature of Ce3+ is that it is more likely to remain on the polished surface, having the potential to induce defectivity via particle contamination and micro-scratches. To mitigate these defects, industrial methods such as standard clean 1 (SC-1) target the less reactive Ce4+ state to result in angstrom level uniformity using concentrated chemical agents. The focus of this work is to investigate the oxidation state of CeO2 through UV-Vis and fluorescence spectroscopy. Results have shown a decrease in the ratio of Ce4+/Ce3+, which was tracked and correlated to increased removal rates in the presence of key slurry additives. Furthermore, understanding the interactions at the wafer interface are critical in unraveling the effect of the macromolecule and surfactant-based cleaning agents, which was studied using dynamic light scattering to monitor the particle size and zeta potential. Analogous to SC-1, the cleaning chemistry shows comparable particle removal using fluorescence microscopy; however at an increased efficiency, making it a viable alternative to traditional cleaning methods. Ultimately, both CMP and post-CMP processes have shown improvement through the understanding of the CeO2 oxidation states, along with the particle encapsulated removal mechanism.

Role of slurry chemistry on the nanoparticle redox behavior relevant to the shallow trench isolation chemical mechanical planarization process

256th National Meeting (2018)

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