Effect of Pressure on the Static Forces of Micron-Scale Particle Adhesion

Supercritical or liquid carbon dioxide has been proposed as an environmentally benign solvent for precision cleaning. In this work, a model is presented that describes the static forces responsible for adhesion of microscopic particles to solid surfaces with a fluid layer present on the surface. This model is descriptive of particle adhesion in precision cleaning applications, such as cleaning of microelectronic devices. Predictions are made for the effects of high pressure on an idealized particle/fluid/surface system. The idealized system is a 1 μm graphite particle on a metal surface that is contaminated with a thin layer of n-dodecane. Calculations predict that the high pressures (as would be required for liquid or supercritical CO2 cleaning) can increase the particle−surface separation distance in some regions of temperature−pressure space and that this effect may be coupled with a decrease in the total adhesion force. This model is useful as a first approximation to the design and analysis of dense-phase CO2-based precision cleaning systems.