Semiconductor Wafer Cleaning Using Megasonics

Megasonic cleaning is routinely used in the semiconductor industry to remove particle contaminants from wafer and mask surfaces. Cleaning is achieved through proper choice of chemical solutions, power density & frequency of acoustic field. Considerable work has been done to increase the understanding of particle removal mechanisms in megasonic cleaning using different solution chemistries with varying ionic strengths. However, to date, the focus of all these studies of particle re-moval has been either cavitation or acoustic streaming. It is well known that the propagation of sound through a colloidal dispersion containing ions results in the generation of two types of oscillating electric potentials, namely, Ionic Vibration Potential & Colloid Vibration Potential. This book reviews some of the current work that shows that these potentials and their associated electric fields can exert significant forces on charged particles adhered to a surface, resulting in their removal.