Post-CMP cleaning using acoustic streaming

Noncontact surface cleaning is a desirable process in post-chemical mechanical polishing cleaning. High-frequency megasonic cleaning utilizes acoustic streaming as the dominant particle removal mechanism. It is widely used in the semiconductor industry for the removal of particulate contamination. This paper introduces recent results that involve the removal of silica slurry using megasonic cleaning. A noncontact (megasonic) cleaning process for the removal of slurry residues from dipped and polished wafers is presented. Complete particle removal (100%) was achieved using megasonics with deionized water with 1% NH₄OH using wafers dipped in silica slurry. The optimum conditions for megasonic cleaning (power, temperature, and time) were determined for the removal of the silica slurry. Up to 99% particle removal from polished wafers was accomplished using noncontact megasonic cleaning with 1% ammonia for 15 min.