Comparison of aluminum post etch cleaning on MEMS structures using formulated organic solvent cleaners

The formulated organic solvent cleaners for aluminum (Al) post etch residues removal have been available on the market for many years. They are used in large quantities in the fabrication of integrated circuits with aluminum interconnects. However, the effectiveness of these chemistries on the aluminum MEMS structures is less well known. In this study, we compared the effectiveness of four different formulated organic solvent chemistries for Al post etch residues removal for certain types of aluminum MEMS structures. The four different formulated solvent clean chemistries evaluated in this study were ST250 from Advanced Technology Materials Incorporated (ATMI), NE14 and ACT690S from Air Products (AP), and EKC265 from DuPont. Both ST250 and NE14 were implemented in a single wafer cleaner as they are typically used in a single wafer cleaning environment. ACT690S and EKC265 were implemented in a tank on a wet bench as they were formulated to work in total immersion environment. Short loop wafers of Al MEMS structures of several microns in sizes were etched in a DPS (Decoupled Plasma Source) metal etch chamber using Cl₂/BCl₃ plasma followed by H₂O-based plasma photoresist strip in an ASP (Advanced Strip and Passivation) chamber on the Centura etch platform. These wafers were then cleaned in one of the four different solvent chemistries for comparison. We found that each organic solvent cleaner has its own advantages and disadvantages in cleaning efficiency, cost, as well as the post etch metal corrosion. For each and every organic solvent cleaner, the process conditions during cleaning must be optimized in order to achieve the best results for residues removal and corrosion prevention.