Chemical mechanical planarization of germanium using oxone(R) based silica slurries

In this study, the etch rate (ER) and the removal rate (RR) of germanium using oxone based silica chemical mechanical planarization (CMP) slurries have been investigated. In the dissolution study, the Ge ER was found to increase with increase in pH from 3 to 11. It was also observed that Ge ER increased initially with oxone concentration and then levelled off. The dependency of Ge RR on oxone concentration, abrasive concentration and pH of the slurry were also studied. There was no significant RR, when Ge coupon was polished with 3 wt% silica in the absence of oxone. Higher RR in the presence of 3 wt% fumed silica and 1 wt% oxone could be explained as due to the synergetic effect of chemical etching and abrasive polishing provided by oxone and fumed silica respectively. It was observed that Ge removal rate follows non-Prestonian behaviour. Removal of Ge is due to oxidation of Ge to form GeO2, which was favoured by the dissociation of oxone and subsequently hydrolysed to form soluble Ge hydroxides at alkaline pH values. (C)2017 Elsevier B.V. All rights reserved.