Effect of pH Value and Glycine in Alkaline CMP Slurry on the Corrosion of Aluminum by Electrochemical Analysis

Abstract

As the feature size of integrated circuit (IC) shrinks down to 28nm and below, Aluminum (Al) is considered to be one of the suitable gate materials. During chemical mechanical polishing (CMP) of the Al gate, Al is very easy to be scratched. The purpose of Al gate polishing is to achieve effective removal and improve surface quality. The pH value and additives of slurry are critical factors affecting the material removal rate and the surface quality. Taking the advantage of enhancing chemical action and solubility of product in CMP process, the potentio dynamic polarization measurements with dynamic impedance monitoring were performed to evaluate the effects of pH value and glycine on the behavior of the electrochemical corrosion. The results showed that the corrosion potential decreased as the pH value and glycine concentration increased. Meanwhile, the dissolution rate and reversing proportion to the polarization resistance increased with the increasing of pH value and glycine concentration, the removal rate of by-products (Al(OH)3) from the interfacial reaction accelerated, and the chemical adsorption of NH2−group identified by FTIR was converted into a soluble form, the removal rate was increased from 216 Å/min to 594 Å/min, and the surface roughness was greatly reduced from 18.6nm to 1.57nm. The synergetic effects of pH and glycine, combined with the analysis of the EIS for the aluminum alkaline CMP, indicated the RR and the surface quality of aluminum after CMP was obviously improved due to the chemical dissolution efficiency of interfacial by-product enhanced.