Chemical Mechanical Planarization of Germanium using Polymorphs of Titania as Abrasive and Hydrogen Peroxide

Abstract

Abstract In the present work, chemical mechanical planarization (CMP) slurry was formulated for polishing germanium (Ge) using rutile (titania (R)) and anatase (titania (A)) titania as abrasive and hydrogen peroxide (H2O2) as oxidizer. CMP experiments were carried out at identical process conditions with different polymorphs of titania abrasives to understand the role of abrasive on Ge material removal rate (MRR) in the presence and absence of hydrogen peroxide. Etch rate (ER) was calculated based on dissolution study to understand the reaction chemistry with Ge. The effect of pH, rotational speed of platen, pressure and hydrogen peroxide concentration of both polymorphs on Ge removal rate was investigated. Higher MRR and ER of Ge were obtained in alkaline region at pH 11 as compared to the acidic and neutral region. Surface area of titania polymorphs were measured using accelerated surface area and porosimetry system (ASAP). Transmission electron microscopy (TEM) results reveal that the particle size of the both the polymorphs was found to be less than 100 nm. Average particle size of abrasives, calculated using Sauter formula, was found to be 19.4 nm for titania (A) and 21.8 nm for titania (R).