Evacuation-driven smif pod purge system

Abstract

A system for providing uniform, controlled and efficient purge gas flow rates and gas flow patterns for removing contaminants and/or particulates from wafers within a pod. The purge system includes seals at the interfaces between the gas inlet and removal lines to substantially prevent leakage at the interfaces. The system may establish seals at the inlet and outlet without having to use conventional fluid flow pins extending above the support surface. The negative pressure applied at the outlet controls the flow rate through the pod, and the rate at which gas leaves the pod will limit the rate at which gas may enter the pod. In a preferred embodiment, the inlet flow is approximately equal to the outlet flow. With substantially equal inlet and outlet pressures, the purging gas flows through the upper and lower portions of the pod in a substantially uniform flow pattern so that contaminants and particulates are removed evenly from wafers throughout the pod. As an alternative to the normal purge and/or trickle modes of operation, the system may remove a volume of gas from a pod and replace it with a new volume of gas by operating the low pressure source with the high pressure source turned off. Further still, the flow lines may include flow rate control systems that provide purging flow for a predetermined time interval, and thereafter provide a trickle flow as long as the pod is seated on the support surface.