Chemical Mechanical Polishing of InP

Abstract

Results of a detailed study of different parameters of the polishing process and their influence on the removal rates (RRs) of InP are presented. RRs with silica-based slurries as well as generation of PH3 were much higher in the acidic pH regions compared to those in basic pH regions. RRs were also higher than those obtained with harder alumina particles. Smaller silica particles led to higher RRs than larger particles at the same wt% loading, presumably due to the higher total particle surface area. These characteristics suggest an affinity between silica particles and InP similar to that observed earlier between Ta and silica. However, unlike with Ta, replacing the surface silanol groups of the silica particles with dimethyl silane did not suppress the RRs completely. It is proposed that InP removal by silica abrasives is facilitated by the formation of –Si–O–In–, –Si–In– and –Si–P– structures due not only to the reactivity of the silanol groups but also due to the combined effect of the electronegativity of Si atoms, the presence of lone pairs of electrons on In atoms on the InP surface and the electronegativity difference between Si and P.