Small Molecule Adsorption on Colloidal Alumina and Zirconia Abrasives Used in Chemical-Mechanical Planarization (CMP) Slurries

Abstract

Small molecule adsorption on CMP slurry abrasive particles has been investigated previously for silica (1) and ceria (2, 3) abrasives using fluorescence correlation spectroscopy (FCS) and attenuated total reflectance – Fourier transform infrared spectroscopy (ATR-FTIR). The need for further characterization of such adsorptive interactions is dictated by the increasing use of abrasive particles in CMP slurries with minimized hydrodynamic diameters (≤ 10 nm) as a means to reduce surface defects created during CMP processes. Incorporation of ever-smaller abrasive particles in CMP slurries will, however, promote the adsorption of chemical additives on a slurry’s abrasive particles due to the increase in the total abrasive particle surface area. In the present study, FCS and ATR-FTIR are employed in the analysis of small molecule adsorption on colloidal alumina and zirconia abrasive particles. This work is motivated by the widespread commercial use of alumina-based slurries in CMP processes for planarization of deposited copper films on dielectric layers and the proposed use (4) of zirconia abrasives in CMP slurries for metal film removal on dielectric metal oxide materials. The reported FCS studies use fluorescent dyes as probes for adsorption sites on alumina and zirconia colloids dispersed in aqueous solution. Described ATR-FTIR analyses summarize the characterization of molecular interactions driving glycine and picolinic acid adsorption on porous thin films of colloidal alumina and zirconia, respectively. The potential for employing these methods in studies modelling the adsorption of CMP slurry additives on a metal film deposited on a silicon wafer surface is also discussed.