Evaluation of High-Speed Linear Air-Knife Based Wafer Dryer

Abstract

With the downscaling of devices, due to device geometry shrinkage, the total number of cleaning steps has increased dramatically. As a result, the number of drying cycles after cleaning has increased as well. As the device shrinks with the integration density increase, it is noteworthy that a perfect drying efficiency is mandatory to obtain a high performance device [. Basically, the mechanism of wafer drying in semiconductor industry can be explained as: first reducing the amount of liquid on the wafer surface by mechanical forces. There are some approaches for removing the liquid such as spinning, high pressure gas blowing by nozzle or air-jet, vertical withdrawal from the liquid bath, using surface gradient tension and so on [2]. Second: if the mechanical forces in the liquid removal part are not sufficient for drying and some droplets or a thin liquid layer remain on the wafer surface, complete drying will be achieved by evaporation of the remaining layer on the wafer. After this evaporation step, known as state transformation, the wafers will be completely dried. Evaporation of the remaining liquid layer is the main mechanism for generating drying defects (watermarks, residues, particles, and etc.)[3]. In this study, we propose a new methodology for semiconductor wafer drying based on a high-pressure gas flow. In comparison to conventional drying tools, the new drying set up combines high speed drying (wafer drying time down to 2 sec at 150mm.s-1) and a low number of added drying defects.