Development and Verification of a

Highly Dispersed Iron Oxide Nanoparticle Solution

News from Member - CMS/ITRI, Chinese Taipei

Highly Dispersed Iron Oxide Nanoparticle solution

As semiconductor technologies continue to scale down to smaller nodes, analytical techniques and instruments face increasing challenges in detecting ultrafine particulate contaminants. A key limitation is the absence of suitable reference materials (RMs) for characterizing nanoparticles at ultra-low concentrations in high-purity chemical matrices.

To address this need, Center for Measurement Standards (CMS/ITRI) has developed a highly dispersed iron oxide nanoparticle solution compliant with the ISO 17034 framework. Both parts-per-million (ppm) and parts-per-billion (ppb) iron oxide nanoparticle solutions were prepared, with surface treatments applied to ensure long-term dispersion stability.

The ppm-level solution was evaluated for batch homogeneity and stability using dynamic light scattering (DLS) and zeta potential measurements, while the ppb-level solution was characterized using single-particle inductively coupled plasma mass spectrometry (spICP-MS), assessing particle size and count under controlled isothermal conditions (4 °C, 25 °C, and 40 °C). Homogeneity testing across 10 bottles per batch yielded an average particle size of 31.0 nm with a relative standard deviation of 2.4 %. A ±3σ threshold was used to define failure criteria for stability.

Results indicates that the solution stored at 4 °C maintained particle size and zeta potential within a 5 % variation over 12 weeks—well within the defined tolerance limits—demonstrating strong potential as a stable reference material. The ppb-level solution also exhibited excellent short-term stability, with variations in particle size and number remaining within 3 % after three months at 4 °C and 25 °C. Slight aggregation was observed after four weeks at 40 °C, suggesting that storage at lower temperatures is preferable.

These nanoparticle solution batches meet the preliminary stability requirements of ISO 17034 and will undergo a six-month extended study to establish a comprehensive stability model. The outcomes are expected to strengthen traceable nanoparticle measurement capabilities, enhance QA/QC processes across the advanced materials supply chain, and reinforce Taiwan’s role in global reference material development and advanced metrology.

Dr. Chiu-Hun Su

ch.su@itri.org.tw