Splash suppression during wafer wet cleaning through drop penetration across metal meshes and porous fiber mats

Abstract

Semiconducting silicon wafers were subjected to centrifugal wet cleaning to remove micro-contaminants. The circular wafers were rotated while a cleaning liquid was supplied to the wafer surface. During such a cleaning process, the centrifugal force atomizes the liquid film at the wafer edges, producing drops. These drops travel in the confined chamber, collide with the chamber walls, and form splashed droplets. Thereafter, the splashed droplets return to the wafer, thereby significantly increasing the risk of re-contamination. Given this wafer wet cleaning scenario, we experimentally investigated the trajectories of splashed droplets. We introduced metal mesh filtration and air-blowing techniques to minimize wafer re-contamination by the splashed droplets. The metal mesh decreased the speed of the drops, thus minimizing the intensity of splashing. The droplets were also air-blown with a supersonic stream to deflect the droplets from their trajectories and thus prevent them from reaching the wafer. The optimal air-blowing condition was determined through parametric studies. The metal mesh was electroplated with copper, producing textured surfaces on the mesh wires. In addition, the metal fiber mats were laminated on the metal mesh and the effects of these on splashing were studied. Further, photographs of droplets spreading and splashing over these metal meshes were captured to elucidate their detailed dynamics. Time-series snapshots of drops penetrating the metal meshes were also captured. Graphic abstract