CHEMOMECHANICAL POLISHING OF SILICA AND SILICON BY FLUORIDE-BASED ANDOXIDE-BASED REAGENTS - IDENTIFICATION OF A REACTION INTERMEDIATE

The effect of added hydrogendifluoride anion on the chemomechanical po lishing of silica and silicon wafers by aqueous suspensions of cerium( IV) or silicon(IV) oxides has been investigated over a range of soluti on pH. The effect on silica is marked at very low pH; an intermediate under these conditions has been identified as K2SiF6 coated with a thi n silica-like layer. The [HF2](-) anion is ineffective for silica poli shing above pH 7 and for silicon under all conditions examined. The mo st effective reagent for the latter substrate is a mixture of cerium(I V) oxide and alkaline silica sol. An explanation for the role of [HF2] (-) is offered.