Dynamic modelling and simulation of a cryogenic carbon dioxide cleaning process

In this study, a model is described that explains the detachment mechanism of a contaminant particle adhering to a substrate, a phenomenon that typically occurs in cryogenic carbon dioxide cleaning processes widely employed in the microelectronic industry. To this end, a theoretical modelling study is performed, and it uses the Lennard-Jones potential theory for a rough surface to describe the contact, adhesion, deformation, and movement mechanisms of the particle on a substrate. To avoid the occurrence of mathematical singularities, the contact and adhesion problem is carefully stated. The contact and adhesion pressures are then computed with respect to the mean separation distance. This is followed by a dynamic simulation study that examines the effects of impact velocities of a CO₂ snow particle on the detachment of a contaminant particle. A criterion for the detachment of a contaminant particle is established, and the behaviour of this criterion with respect to the contact angle is investigated. The critical impact velocity required to detach the contaminant particle from the substrate is determined with respect to the impact angle and the CO₂ snow particle size. Finally, the limitations of this modelling approach and the implications of the results in understanding the cleaning process are discussed.