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Journal of the Electrochemical Society, Vol.158, No.11, H1152-H1160, 2011
Chemical Mechanical Polishing of Ge in Hydrogen Peroxide-Based Silica Slurries: Role of Ionic Strength
Increasing the ionic strength (I) of a silica-based slurry containing H(2)O(2), using different electrolytes (KNO(3), KCl, NaNO(3) and K(2)SO(4)), 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% H(2)O(2), the RRs were about similar to 300 nm/min at I = 0.003 M and increased to similar 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 similar to 0 nm/min while the RR was still similar to 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 GeO(2) facilitated by the adsorption of the cations. The oxide is hydrolyzed and removed easily at neutral and basic pH values. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.055111jes] All rights reserved.