ABSTRACT
A necessary prerequisite to obtaining high yields in very large-scale integrated (VLSI) fabrication is the ability to keep wafers scrupulously clean. It is important to note that the forces of adhesion that hold particles on surfaces are strong functions of the particles' chemical composition, size, shape, and environment. Hence, the selection of an appropriate cleaning technology depends on a correct understanding of these factors. The principal interactions associated with particle adhesion include molecular (van der Waals) interactions, electrostatic interactions, hydrophobic/hydrophilic interactions, steric interactions, and chemical bonding. For any material, the van der Waals interaction is characterized by a descriptor known as the Hamaker constant. The electrostatic force of adhesion is made up of coulombic attractions and electrostatic contact potentials. The more important electrostatic force for very small particles is the electronic double-layer force induced by electrostatic contact potential.
