Defectivity and Yield Impact From the AMC Inside the FOUP in Advanced Technologies
John Adair Barker, Stephen Miner, Wei Zhao, Jong Soo Kim, Joshua Moore, Eswar Ramanathan, S. L. Case, Stephanie Waite · IEEE Transactions on Semiconductor Manufacturing · 2017
Historically, much attention has been given to the unit processes and the integration of those unit processes to improve product yield. Less attention has been given to the wafer mini environment, either during processing or post processing. This paper contains a detailed discussion on how particles and airborne molecular contaminants (AMCs) from the wafer mini environment interact and produce undesired effects on the wafer which in turn cause devices to fail. Sources of wafer environmental contamination are the processes themselves, ambient environment, outgassing from wafers, and front open unified pod (FOUP) contamination. Establishing a strategy that reduces contamination inside the FOUP mini environment will decrease defect variability and thus increase yield. In manufacturing ecosystem, changing the FOUP or moving the wafers faster or purging with nitrogen to reduce the impact from mini environment is not always an option. Alternative to having a stop gap, it is desired to understand the AMCs and thus exploring sustainable solutions to minimize them below certain thresholds that would cause impact on wafer. NH3-based contamination, extensively discussed in this paper, is observed to cause wafer defects. Thus, explicit knowledge of AMC type is critical, as the most optimized methodology to control various AMCs might not always be the same. Three primary variables that greatly impact this strategy are FOUP contamination mitigation, FOUP material, FOUP metrology, and cleaning method.