Detecting large particles in a slurry by measuring acoustic cavitation thresholds

Acoustic microcavitation is used to detect particles in liquids and suspensions. The observation that an acoustic cavitation threshold is characteristic of particle size is exploited to develop a solution for an important problem facing chemical mechanical planarization of silicon wafers. Specifically, it is established via experiments that a sparse presence of large particles in a nanofine slurry can be detected acoustically. Being able to detect such large particles prior to chemical mechanical planarization polishing is expected to save the wafers from being scratched during planarization. The acoustic method is entirely noninvasive.