Stabilization of alumina slurries containing
Fe(NO3)3 and benzotriazole (BTA) for
chemical−mechanical
polishing (CMP) of copper in acidic media was investigated. Slurry
stability was evaluated from the initial
settling rate of alumina particles in well-dispersed slurries. ζ
potential and FTIR spectroscopy were
employed to elucidate the observed effects. Fe3+,
used as an etchant for copper, did not affect the slurry
stability significantly, especially at low concentrations (<0.05 M).
However, BTA worsened the stability,
especially at higher concentrations, by reducing the electrostatic
repulsion between alumina particles.
This was confirmed by a drop in the measured ζ potential.
FTIR spectra showed that BTA is chemisorbed
onto alumina particle surfaces. Finally, the addition of
poly(ethylene glycol) (MW = 1 000 000) improved
the slurry stability significantly and a stable alumina slurry for the
CMP of copper was obtained. Preliminary
data on the removal rates of copper and the selectivities of removal
between SiO2 and Cu using these
slurries are reported.
Copper dissolution in ammonia-containing media during
chemical-mechanical polishing
(CMP) was investigated. Both a stationary and a rotating disk
electrode (RDE) were used
for electrochemical characterization. Ammonia can etch copper in
the presence of oxidizers
by dissolving the oxide film on the copper surface and the dissolution
rate varied from about
8 to 30 nm/min, depending on the hydrodynamic conditions. The
copper dissolution rate in
NH4NO3 or
(NH4)2SO4 solution does not
vary significantly with solution pH. Ammonium
nitrate results in a higher dissolution rate, due to the extra
oxidizing power of the nitrate
ion. The addition of an inhibitor, benzotriazole (BTA), reduces
the copper dissolution rate
significantly, even though the dissolution rate can be increased by
rotating the copper disk.
The dissolution of copper in stagnant aqueous ammonia solutions is
controlled by oxygen
diffusion at high NH4OH concentrations and by mixed
kinetics at low NH4OH concentrations
(≤0.3 wt %).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.