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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.

The subject of this report is the characterization of plasma etch residues after a metal etch process with Cl2/BCl3 etch gases. One of the interactive factors in the removability of the residues is the photo-mask removal process (DSQ). Depending on the DSQ process the molecular structure of the residues will differ. For our findings, we used laser spectroscopy and Fourier-transformed infrared spectroscopy to obtain information about the degree of the cross-linking of the molecular structure of residues in a post-metal etch cleaning process. The post-etch cleaning is important for removing residues remaining after the metal structuring process. The main goal is to use emission spectroscopy for studying the compounds of the dry-etch related residues. Finally, it was shown that small variations in wafer treatment directly after dry-etching results in different solubilities of residues in HDA (hydroxylamine) based solutions. [1]