Analysis of 50 nm Silica Nanoparticles in Semiconductor Process Chemicals by spICP-MS/MS

Importance of Topic

Semiconductor device yields and performance critically depend on the purity of process chemicals. Insoluble silica nanoparticles (SiO2 NPs) as small as 50–60 nm can introduce defects and lead to circuit failures. Traditional dissolved element monitoring does not capture particulate contaminants. Implementing a reliable, sensitive method to detect and characterize trace silica nanoparticles in high-purity acids and solvents is essential for advanced integrated circuit fabrication and quality control.

Study Objectives and Overview

This application note describes the development and validation of a single-particle ICP-MS/MS (spICP-MS/MS) method using an Agilent 8900 ICP-QQQ instrument. The main goals were to achieve accurate detection, sizing, and quantitation of 50 nm silica nanoparticles in semiconductor‐grade hydrochloric acid (HCl), sulfuric acid (H2SO4), and isopropyl alcohol (IPA), while overcoming spectral interferences and matrix challenges.

Methodology

Sample preparation involved diluting 98 % H2SO4 by 100× or 200×, 36 % HCl by 5× in ultrapure water, and directly analyzing undiluted IPA. Certified SiO2 NP standards (50, 60, 100 nm) were spiked into each matrix at defined concentrations (10–60 ppt). Fast time-resolved analysis mode with 0.1 ms dwell time was used. A data processing module automatically discriminated single-particle events from ionic background and calculated particle size distributions and number concentrations.

Instrumentation

• Agilent 8900 ICP-QQQ (semiconductor configuration) operated in MS/MS mode
• Hydrogen cell gas in ORS4 to remove 14N2+ and 12C16O+ interferences at m/z 28
• Agilent SPS 4 autosampler and PFA nebulizer for self-aspiration
• Standard quartz torch (2.5 mm injector for acids, 1.5 mm injector for IPA), quartz spray chamber, platinum-tipped interface cones

Main Results and Discussion

• In ultrapure water, mixed 50 nm and 100 nm SiO2 NPs were clearly resolved, with measured mean diameters of 50 nm and 99 nm respectively.
• In 7.2 % HCl, a 20 ppt spike of 50 nm NPs produced a 22 ppt recovery with well-defined signal and size distributions.
• In 1 % H2SO4, 50 nm NPs remained distinguishable from background, confirming effective interference removal.
• A 10-hour stability test with 100 nm NPs in 200×‐diluted H2SO4 showed constant particle concentration and size, verifying nanoparticle insolubility and method stability.
• In undiluted IPA, 60 nm NPs were detected despite the carbon matrix, demonstrating successful CO interference elimination by H2 cell gas.

Benefits and Practical Applications

• Enables simultaneous measurement of nanoparticle size, number concentration, and dissolved elements using one instrument.
• High sensitivity and selectivity provided by MS/MS and hydrogen cell gas allow detection of 50–60 nm SiO2 NPs in aggressive matrices.
• Automated data analysis streamlines integration into QC/QA programs for semiconductor chemical suppliers and fabs.

Future Trends and Potential Applications

As devices shrink further, monitoring sub-50 nm particulate contamination will become more critical. Advances in plasma sources and cell chemistry may improve sensitivity for even smaller NPs and a broader range of materials. Integration with real-time process analytics and machine-learning-based data interpretation could enhance predictive maintenance and yield optimization.

Conclusion

The Agilent 8900 ICP-QQQ in spICP-MS/MS mode provides a robust, sensitive platform for detecting and characterizing 50–100 nm silica nanoparticles in high-purity acids and solvents. Effective removal of N2 and CO interferences by hydrogen cell gas, combined with fast time-resolved acquisition, delivers accurate size and concentration measurements. This method supports stringent QC requirements in semiconductor manufacturing.

References

• Measuring Inorganic Impurities in Semiconductor Manufacturing, Agilent publication 5991-9495EN
• Shimamura Y, Hsu D, Yamanaka M. Multielement NP Analysis of Process Chemicals Using spICP-QQQ, Agilent 5994-0987EN
• Shimamura Y. Elemental and Particle Analysis of N-Methyl-2-Pyrrolidone by ICP-MS/MS, Agilent 5994-5365EN
• Yamanaka M, Itagaki T. High-sensitivity Analysis of SiO2 NPs with Agilent 8900 ICP-QQQ MS/MS, Agilent 5991-6596EN
• Hsu D, Shimamura Y, Liao B, et al. Analysis of NPs in Organic Reagents by Agilent 8900 ICP-QQQ spICP-MS, Agilent 5994-1306EN
• Nakano K. Ultralow Level Determination of P, S, Si, Cl Using Agilent 8900 ICP-QQQ, Agilent 5991-6852EN