Particle Reduction on Silicon Wafers as a Result of Isopropyl Alcohol Vapor Displacement drying after Wet Processing

The presence of particles on the surfaces of semiconductor wafers is known to negatively affect device yields. As linewidths continue to shrink, the inherent limitations in many of the commonly used methods for drying wafers after wet processing have created the need for alternatives which offer better particle control. In this paper the use of IPA vapor displacement drying was examined as a means to dry wafers. Wafers were immersed in water in an enclosed chamber, and IPA vapor was then released into the top of the chamber while the water was pumped out through the bottom. Physical observation of drop formation on the wafers indicated both temperature and drain rate are important factors in effective drying with this method. When a commercial apparatus applying these principles was used to dry wafers in a Class 10 clean room, fewer than two particles greater than 0.5μm in diameter were routinely added to l00mm wafers, confirming the practical applicability of the findings.