The Influence of Solution Properties on the Deposition of Particles from Liquid Media onto Silicon Wafer Surfaces

Abstract

Measurements were made of the deposition of negatively-charged particles (soda-lime glass) and positively-charged particles (aminopropyl glass) from liquid solutions onto silicon wafers with a native oxide. The effects of ionic strength and the pH of the solution on the magnitude and the mechanism of particle deposition were determined by measuring the number of deposited particles in the presence of KC1, KOH and HC1 in a concentration range from 10−5 M to 10−1 M. The results are compared to deposition measurements made in 18 MΩ deionized water. Increasing ionic strength can reduce the particle deposition in systems where a double layer attraction exists, but increase the particle deposition in systems experiencing a double layer repulsion. The influence of pH on deposition was found to depend strongly upon the isoelectric point of both the particle and the wafer. The results of deposition experiments can be readily interpreted in terms of the potential energy of interaction which exists between the particles and the wafer surfaces.