Studies of the relationship between megasonics, surface etching, and particle removal in SC-1 solutions

Wafer cleaning studies have been performed so as to understand the influence of acoustic (megasonic) energy on particle removal in dilute SC-1 solutions. Surface etching alone (up to 60angstrom) has been found to be insufficient to completely remove silicon nitride surface particles from native oxide surfaces in the absence of megasonics. For megasonic cleaning processes the minimum surface etching required for complete nitride particle removal is significantly lower (between 3-12 angstrom) than for a non-megasonic process. The exact 'threshold' for surface etching will depend on the chemical nature of the particle/surface and the megasonics power. Megasonics energy does not appear to enhance chemical etching of the substrate, at least for silicon oxide substrates, however, it significantly improves particle removal. This data suggests that the particle removal process can benefit from both a thermally activated component (etching) as well as an acoustic component (cavitation/acoustic streaming).