The watermark formation mechanism at the three-phase interface of the droplet on the semiconductor wafer was experimentally investigated. The behavior of fluorescence particles near the wall was visualized using evanescent light generated by total reflection at prism surface. The test solution was ultrapure water, and its droplets were formed on the prism surface. The behavior of particles at the three-phase interface of the droplet was observed by fluorescence and the scattering of evanescent light. Temporal changes in the contact angle and fluorescence intensity were analyzed. According to the experimental results, it was observed that the fine particles in the droplet tended to agglomerate at the three-phase interface, and it was found that the fluorescence intensity near the three-phase interface increased with evaporation.
YAMAMOTO et al. (Wed,) studied this question.