Chemo-Mechanical Planarization of Germanium Using Potassium Periodate based Titania Slurries

Abstract:
In the present study, the etch rate (ER) and the removal rate (RR) of germanium using potassium metaperiodate (KIO4) as oxidizer in titania (anatase) based chemical mechanical planarization (CMP) slurries have been investigated. The solubilty of KIO4 is enhanced by addition of 0.1M KOH in the solution. In the dissolution study, ER of Ge was found to increase with pH from 3 to 11, initially ER with KIO4 concentration increases and then gets levelled off. The dependency of Ge RR on KIO4 concentration, pH of the slurry, turntable speed and down pressure were also studied. Polishing only with 1 wt% titania showed no significant removal. RR was observed when Ge coupon was polished with 1 wt% titania in presence of 1 wt% KIO4 + 0.1M KOH. Higher RR of titania slurry, in the presence of 1 wt% KIO4 + 0.1M KOH could be explained as due to the synergetic effect of chemical etching and abrasive polishing. In the presence of KIO4 removal is due to oxidation of Ge to form GeO2, with subsequent oxidation to form soluble species. It was observed that Ge removal rate follows non-Prestonian behaviour. Keywords: Chemical mechanical planarization, Germanium, Anatase titania, Potassium metaperiodate, Removal rate.