High-Removal Selectivity Through Interaction Between Polyacrylamide and SiO2 Film in Poly Isolation Chemical Mechanical Planarization

Abstract

The interaction between polyacrylamide (PAM) and SiO₂ film was investigated in order to elucidate the removal polycrystalline silicon (poly Si) to SiO₂ selectivity in poly isolation chemical mechanical planarization (CMP). The hydrophilic characteristics of poly Si and SiO₂ were analyzed by the X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The surface of SiO₂ is more hydrophilic than that of poly Si due to the siloxane (≡Si—O—Si≡) bonding. The adsorption behavior of PAM on poly Si and SiO₂ film was determined by adsorption isotherms and force measurements using atomic force microscopy (AFM). Interaction between siloxane bonding of SiO₂ film and the amine group along the backbone of PAM results in the adsorption of PAM on SiO₂ film. Consequently, the passivation layer of PAM on the SiO₂ film prevented abrasives from approaching the surface of SiO₂ film, which led to suppression of the removal rate of SiO₂ film from 82 to 12 Å/min in poly isolation CMP process.