Ultratrace Impurity Analysis of Ultrapure Water with Low Boron Background by ICP-MS/MS

Significance of the Topic

The continuous scaling of semiconductor devices demands ultrapure process chemicals to avoid performance degradation and yield loss. Ultrapure water (UPW) plays a critical role in wafer cleaning and surface preparation, and trace levels of elemental impurities, especially boron, must be monitored at sub-ppt concentrations to ensure device reliability.

Study Objectives and Overview

This study evaluates the performance of the Agilent 8900 triple quadrupole ICP-MS (ICP-QQQ) coupled with MS/MS methodology for ultratrace impurity analysis in UPW. A key focus is the determination of boron at levels below 1 ppt and comparison of two UPW purification systems, one equipped with a boron-removal filter.

Methodology and Instrumentation

Sample handling and analysis were optimized through the following steps:

• Extended rinse of the ICP-QQQ system with UPW from a Puric ω II unit for >24 h, followed by a brief 2% HNO3 rinse.
• Collection of UPW directly from the Puric ω II sampling port and bottled system blank.
• Preparation of multi-element calibration standards in 0.1% HNO3.
• Automatic calculation of limits of detection (LOD) and background equivalent concentrations (BEC) using ten replicate measurements of the UPW blank.

Used Instrumentation

• Agilent 8900 ICP-QQQ with s-lens and Octopole Reaction System (ORS4)
• Quartz nebulizer (Agilent part G1820-65138)
• Agilent I-AS autosampler
• Puric ω II UPW production system with boron-removal filter (Organo, Japan)

Key Results and Discussion

The ICP-QQQ method achieved LODs and BECs ranging from low ppq to sub-ppt levels for 28 elements. Notably, boron LOD improved from 0.51 to 0.12 ppt and BEC from 1.2 to 0.63 ppt when using the Puric ω II filter compared to the standard Puric ω system. Silicon and phosphorus also showed low detection limits despite challenging ionization and background interferences.

Benefits and Practical Applications

The demonstrated sub-ppt sensitivity allows semiconductor fabs to monitor critical impurities in UPW with greater confidence, reducing particle defects and contamination events. This method supports stringent QA/QC protocols and ensures consistent process control in advanced node manufacturing.

Future Trends and Potential Uses

Further development may include integration of online ICP-QQQ monitoring for real-time UPW quality control, advanced membrane technologies for selective impurity removal, and coupling with data analytics platforms for predictive maintenance and contamination trend analysis.

Conclusion

The Agilent 8900 ICP-QQQ with MS/MS capability provides exceptional ultratrace analysis performance for UPW, achieving ppq to sub-ppt detection across a broad element range. Efficient boron removal using the Puric ω II system further enhances analytical confidence, supporting the semiconductor industry’s demand for ultra-high purity water.

Reference

• Measuring Inorganic Impurities in Semiconductor Manufacturing, Agilent publication, 5991-9495EN.
• Sakai K, Shimamura Y. Ultrapure Process Chemicals Analysis by ICP-QQQ with Hot Plasma Conditions, Agilent publication, 5994-4025EN.