Testing the use of purge gas in wafer storage and transport containers

摘要

While the use of minienvironments and automated containers is spreading in the IC manufacturing industry, the damage such enclosed environments can cause, even when purged, is worrisome. Based on the specific case of gate oxide preservation, this article has demonstrated that using a purge gas in storage containers is problematic. Indeed, the use of a dry purge gas or residual organic contamination, which is present even in purified gas, can have a detrimental impact on electrical device performances. The experiments presented in this article demonstrate that not all container materials have a similar effect on the wafers stored in them. Although new-generation containers, such as single-wafer FOUPs, ensure better storage conditions than conventional polypropylene boxes, not even sealed quartz containers meet ITRS recommendations for long-term storage. Finally, the tests discussed here indicate that the qualitative nature of organic contamination has at least as much of an impact on intrinsic electrical device performance as the quantitative amounts of organic contaminants present on the wafer surface. Unfortunately, the qualitative nature of organic contamination has yet to be seriously considered in efforts to determine hazard thresholds.