Impact of Dry Etch and Ash Conditions on Removability of Plasma Etch Residues in Al-Metallization. Approach to Improve PER Cleaning Efficiency by EHS-Friendly Aqueous Remover

Driven by cost saving pressure and new regulations such as REACH, the imple¬mentation of cost efficient, EHS-friendly alternatives is in full swing. There is a clear trend in the plasma etch residue (PER) cleaning field to replace the currently used, expensive and harmful organic PER-removers by EHS-friendly aqueous alternatives. Striking advantages of fluorine free aqueous removal are reported1. The goals of present work -which was carried out in cooperation of BASF and Infineon-, was to examine the dependence of residue constitution on etch and strip conditions and to find a way to adapt also most critical cleaning challenges for EHS-friendly PER remover usage. For that reason a selected aluminum interconnect metal layer with difficult removable residues was chosen. XPS is well proved as an appropriate method for selective sidewall and top/bottom residue analysis2. Our analytical work was focused on defining fingerprints for the etch residues, concerning their elemental distribution, and tracking their changes during the different process steps and conditions.