| In integrated circuit (IC) manufacturing, particulate contamination from hundreds of processe steps is a major cause of yield loss. The removal of particles is typically achieved through liquid chemical formulations aided by a sound field in the MHz frequency range. When liquid is irradiated with megasonic waves, dissolved gases play an important role in particle removal and feature damage. To take the advantage of the beneficial effect of CO 2 (aq.), this thesis describes the development and optimization of a megasonic cleaning process using a chemical system containing NH4OH and NH4HCO3 at an alkaline pH in which a specific amount of aqueous CO2 can be maintained to minimize feature damage. In addition, certain etching effects at a slightly alkaline pH were supported for achieving high particle removal. Sonoluminescence (SL) data were collected from these cleaning solutions and correlated with the cleaning performance. The intensity of SL is believed to be a sensitive indicator of transient cavitation during megasonic irradiation, which is thought to be responsible for fragile feature damage. To further analyze the SL signal with respect to the emission from hydroxyl radicals, single-band filters were used to collect the SL signal in different wavelength ranges. |
