The removal of contamination particles from silicon wafers is critical in the semiconductor
industry. Traditional cleaning techniques encounter difficulties in cleaning
micro and nanometer-sized particles. A promising method that uses acoustically-driven
micro-bubbles to clean contaminated surfaces has been reported. However,
little is understood about the microscopic interaction between the micro-bubble and
particle. This thesis explores the mechanism underlying the ultrasonic cleaning using
micro-bubbles at the micrometer scale. The investigation was carried out from
the perspective of bubble dynamics near a surface and bubble-particle interaction.
Prior to contributing to the particle removal, micro-bubbles normally need to be
transported to a target surface. The motion of a bubble was analyzed based on a
force balance model for single and multi-bubble translations respectively. A good
agreement is found between the observed bubble movement trajectories and the
theoretical predictions. After arriving on a surface, a micro-bubble starts to disturb
the flow field near the boundary through its oscillation. The characteristics
of the flow field are closely related to the bubble oscillation modes. The influence of a wall on the change of bubble oscillation mode during its translation toward
the boundary was studied. The relationship between bubble oscillation modes and
the corresponding microstreaming around the bubble was established. The experimental
results of bubble oscillation modes and the flow motion are quantitatively
in good agreement with the simulation results. From a mechanic point of view, a
possible ultrasonic cleaning mechanism is explained by exploring the relationship
between different torques that are exerted on micro and sub-micrometer-sized particles.
This estimation provides a qualitative insight into the ultrasonic cleaning
process at a moderate pressure amplitude. The experimental investigation of the
complicated particle detachment process requires improved test equipment to be
developed in the future.