The adhesion and removal mechanism of Ceria particles for STI post-CMP cleaning process

Abstract

Ceria removal during STI post-CMP cleaning has become a significant concern to the semiconductor industries. Understanding of ceria adhesion and removal mechanisms is very important. In this work, ceria slurries at pH 4 and pH 8 were used to polish oxide surfaces. Their adhesion behavior was affected by the pH of the slurry and the removal behavior was varied as a function of cleaning methods and chemistry used. Different physical cleaning (megasonic and PVA brush) methods and chemical cleaning (SCI, SPM, DHF) methods were compared. During polishing, the particles may attach to the oxide surface electrostatically at pH 4 and through Ce-O-Si bonds at pH 8 conditions. It was found that electrostatically attached particles could be easy to remove whereas Ce-O-Si bonded particles could be removed by strong acidic chemistry such as SPM or DHF. © The Electrochemical Society.