November 27, 2017 03:00:00 PM

Monitoring of Ultrapure Water (UPW) Systems Using the Ultra DI 20

Written by Noelle Demo

Through continuous process and equipment advancements, semiconductor manufacturers are approaching 7 nm feature sizes and heading even smaller, while hard-disk drive fly heights are now less than 10 nm. This ever-reducing device feature size requires comparable cleanliness-level improvements in ultrapure water (UPW). UPW purity is especially important with its high use in direct contact with wafers as a final cleaning and rinsing agent in many production steps. Leveraging recent advances in laser optics and detector technology, the Ultra DI® 20 can effectively monitor UPW particle concentration ≥ 20 nm, or, in the case of metallic particles, ≥ 9 nm. Monitoring is continuous and occurs in real time to enable maximum process control. This industry-leading sizing sensitivity is provided in a system that correlates well with legacy 50 nm particle metrology for data continuity. 

Overview of UPW System
UPW is treated through a multi-step process to meet the high quality standards for leading semiconductor, hard-disk drive and MEMs manufacturing. Advancements in water treatment and filtration at critical UPW facilities provide water at cleanliness levels better than many existing metrology devices can accurately measure. In fact, most modern UPW systems are so clean that there are fewer than 100 particles/Liter greater than 50 nm in size. At these low contamination levels, changes in particle concentration at 50 nm become nearly invisible as they approach detection limits of older instruments. This continuous UPW quality improvement requires a new monitoring solution that can detect significantly smaller particles at very low concentrations.

Within many ultrapure water systems, particle concentration is measured only after the final filtration step. Particle levels need to be as low as possible at the point of use where the water contacts the wafer. It is recommended that the final particle monitoring be located as close to the UPW’s point of use as possible to assure that it is capturing a true measurement of the wafer exposure.


Click here to learn more about how your UPW system can be improved with the Ultra DI 20.