A Study on the Deposition of Particles On Heated Wafers in a FOUP

Abstract

Wafers are packed by 24-25 in a front opening unified pod (FOUP) which moves between equipment by an automated vehicle. Most of the time wafers stand by in the FOUP unless they are under process. The temperature of processed wafers is usually higher than the ambient temperature and this causes natural convection in the FOUP. The particles generated in the FOUP, if any, can move due to natural convection. This study shows the phenomenon of particulate contamination of wafers, induced by natural convection generated inside a plastic enclosure mimicking the FOUP. Both numerical and experimental results showed that the wafer at the top is most vulnerable to contamination by airborne particles in the plastic enclosure. It was found that the degree of particulate contamination of a wafer was dependent on position of the wafer in the plastic enclosure.