Dynamics of the Drying Defects Left by Residual Ultra-Pure Water Droplets on Silicon Substrate

Evaporation of sessile droplets with a small contact angle (below 90°) is studied here extensively on silicon substrates. We focused our work on the origin of the creation of watermarks on silicon wafers. A thorough understanding of droplet evaporation is of vital importance for examining the drying rate, the flow patterns observed inside drying drops, and the residual deposits. The concentration of each potential dissolved species (e.g. silica or silicic acid) can also be predicted and confronted to their solubility. We developed a theoretical model to predict the evaporation rate and the behavior of millimetric droplets taking into account the characteristics of the ambient and the substrate during the drying process. We discuss also the topology of watermarks on silicon wafers in the case of a predominant evaporation phenomenon.