Development of Responsive Polymeric Nanocomposites for Enhanced CeO₂ Removal in Post-Chemical Mechanical Planarization (p-CMP)

Abstract

As integrated circuits (ICs) and logic devices continue to shrink according to Moore’s Law, the demand for enhanced Chemical Mechanical Planarization (CMP) processes has increased dramatically. More specifically, an area that has gained tremendous attention is Shallow Trench Isolation (STI) CMP. The process of STI involves the electrical isolation of active components that require exposure by removing the bulk oxide (i.e., TEOS) overburden from the deposition process. Traditional STI slurry formulations are comprised of a CeO2 nanoparticle dispersion, rate enhancers, selectivity and rheology modifiers, and pH adjusters. Due to the presence of defect states (i.e., oxygen vacancies (Ovacs)) on the surface of CeO2 nanoparticles, their photocatalytic properties can be exploited to induce redox reactions. Specifically, the reduction of Ce4+ to Ce3+ leads to the formation of additional Ovacs on the surface of CeO2, which causes hard adsorption of CeO2 nanoparticles to TEOS surfaces. Significant work has been conducted on optimizing the post-CMP (p-CMP) cleaning process by creating low shear force environments via charge transfer chemistries to remove CeO2 adsorbed to TEOS. As a result, this work presents the design of responsive polymeric composites that may be employed in the brush scrubbing of TEOS to enhance particle removal while minimizing shear and compressive forces. This will ultimately limit secondary defectivity and induce more efficient cleaning of nanoparticles from the dielectric material. To monitor the cleaning process, coefficient of friction (CoF), shear force (SF), defect measurements via profilometry, particle removal efficiency (PRE), and Ce4+/Ce3+ ratio measurements will be utilized. Using a UV/Vis spectroscopic technique to monitor the Ce4+/Ce3+ ratio, initial results show a correlation between the oxidation state of CeO2 and PRE. Additionally, using a non-traditional polymeric brush during cleaning has shown higher PRE while maintaining lower shear force environments.