UPM Community Engagement Manager
Based in Oxford, UK
Metrology; SCREEN; UNISERS; Entegris;
Expert perspectives: What are the industry’s most pressing metrology challenges?
UPM Community Platform Manager Orla McCoy caught up with experts at the 2022 Advanced Semiconductor Manufacturing Conference to understand why metrology is such a significant challenge for the industry.
Siddarth Sampath, Applications Team Lead Liquid Filtration and Purification, and Jennifer Braggin, Director of Technical Training from Entegris agree that metrology is the biggest challenge facing the industry, and that the issue has three main strands. Firstly, metrology limitations can make it impossible to monitor contaminants in water, chemicals, or gases to required purity level. Secondly, in cases where metrology allows adequate collection of data about contaminants and flow rate, analyzing and modelling such a large amount of data is a challenge. Finally, there is a need for greater collaboration and data-sharing between end-users and purification technology providers, as that may be the only way to resolve contamination issues.
Ali Altun, CEO at UNISERS sees similar issues as the main challenges for the industry. Although advanced particle counters can detect sub-50nm particles in ultrapure water, the existing metrology can only reliably count particles sized 50nm or greater.
Secondly, in liquids for wafer cleaning, a standard technology used for detecting contaminants is Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) due to the analytical technology’s ability to detect small, sub-nanometre particles. However, ICP-MS is elemental analysis and molecular analysis is needed for some chemicals namely, polymers. Therefore, chemical identification is a problem, as the elements of a chemical compound can be detected in the liquid on the wafer surface, but the specific contaminants may not necessarily be determined.
Another challenge is how fabs can correlate process defectivity and final yield. Fabs monitor contaminants in both the liquids themselves and the liquids on the wafer surface. Better metrological methods can enable detection of spikes in contaminants in the liquid, which can then provide insights into whether those spikes are causing potential for defects on the wafer. With these capabilities in place, fabs can avoid costly downtimes.
Luke Chang, Program Director from SCREEN SPE USA identifies that the ever-growing and inevitable importance of new device and chip structures will pose the biggest challenge for cleaning process equipment. For example, 3D heterogeneous integration has challenging implications, as it is easy to clean a planar structure, but difficult to clean more complex 3D structures with high aspect ratios. Finding metrology to monitor all aspects of these more complex geometries will pose an additional challenge. Although methods exist for cleaning 3D structures, the industry will need to identify best practices.
Another example which will bring yield difficulties is nanosheet technology, which is expected to replace FinFet transistor technology in the coming years for low-power mobile applications. Nanosheet technology includes very small inner spacers in the structure, so there is the added question of how the industry will identify best practices for measuring and cleaning these spacers.