A special electrostatic self-assembly structure of colloidal silica: Improving Chemical Mechanical Polishing performance

Silica nanoparticles are widely utilized abrasives in chemical mechanical polishing (CMP), and the modification of abrasives and the incorporation of chemical additives represent primary strategies for enhancing CMP performance. In this study, we achieved a modification of the electrical properties of the colloidal silica surface by forming a coating film through the "grafting" of 3-aminopropyltriethoxysilane (APTES) onto the colloidal silica surface. This modification resulted in an augmented mechanical interaction between the abrasive and the wafer during the CMP process, leading to an enhanced material removal rate (MRR) of SiO2. However, the post-CMP surface exhibited a relatively higher occurrence of surface defects. Subsequently, cetyltrimethylammonium bromide (CTAB) was added as an auxiliary additive, which promoted the formation of a "special electrostatic self-assembly structure" on the surface of the abrasive, further elevating the SiO2 MRR. Moreover, CTAB demonstrated the capability to adsorb onto the wafer surface, creating a protective effect that resulted in reduced surface roughness and a decrease in surface defects following CMP. Furthermore, comprehensive characterization of the modified abrasive was conducted using techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanisms underlying the improvement in CMP performance were systematically analyzed through experimental phenomena and X-ray photoelectron spectroscopy (XPS), and revealing that the introduction of CTAB indirectly facilitated the adsorption of APTES onto the surface of the colloidal silica. Our study provides a method for the advanced process of SiO2 CMP with stringent metal ion requirements.