Chemical Mechanical Polishing of Ge in Hydrogen Peroxide-Based Silica Slurries: Role of Ionic Strength

Abstract

Increasing the ionic strength (I) of a silica-based slurry containing H2O2, using different electrolytes (KNO3, KCl, NaNO3 and K2SO4), led to a considerable increase in Ge removal rates (RRs). At pH 9 in the presence of the abrasives (3 wt% silica) and 1 wt% H2O2, the RRs were about ∼300 nm/min at I = 0.003 M and increased to ∼610 nm/min at I = 0.2 M. Above pH 6, the Ge dissolution rates (DRs) also increased with I. However, the addition of 0.1 M Cetyl Trimethyl Ammonium Bromide (CTAB) or Cetyl Pyridinium Bromide (CPB) to the electrolyte-containing slurries suppressed the DRs to ∼0 nm/min while the RR was still ∼450 nm/min. Hence, these process conditions may lead to good planarization. Zeta potentials, DRs, Energy Dispersive Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), particle size distributions, and UV/VIS Spectrophotometric data were used to show that increased ionic strength increases the conversion of Ge to GeO2 facilitated by the adsorption of the cations. The oxide is hydrolyzed and removed easily at neutral and basic pH values.