POST-CMP CLEANING USING A SINGLE WAFER MEGASONIC CLEANER

摘要

A single wafer megasonic cleaning method was developed to address the semiconductor industry need for an integrated dry-in/dry-out CMP process. To remove slurry particles, a piezoelectric transducer transmits sound energy along a quartz rod placed directly above the wafer. The sound is then transmitted to the wafer via a liquid meniscus between the quartz rod and wafer. Sound also reaches the wafer backside by transmission through the wafer. The wafer is held by a spinner and chemical solutions are applied to both sides of the wafer through spray nozzles. Following the cleaning process, rinsing and drying are done on the spinner. Polished wafer experiments demonstrated that the megasonic method gave equivalent defect results as that of a PVA brush scrubber. To help characterize the sound transmission, the impact of the quartz rod/wafer distance was evaluated by slurry removal tests and compared with results from a two-dimensional sound pressure simulation. Both suggest that the optimal quartz rod/wafer distance is between 3/4λ and λ (0.14 to 0.18 cm). Sound transmission was further characterized by evaluating the impact of the length of the quartz rod and by demonstrating removal of defects from the wafer backside.