Direct Measurement of Metallic Impurities in 20% Ammonium Hydroxide by 7700s/7900 ICP-MS

Ammonium hydroxide (NH4OH) is a chemical used in the manufacture of semiconductor devices, and must therefore be analyzed for trace metal impurities. The direct analysis of undiluted (20%) NH4OH using ICP-MS is challenging because its high vapor pressure causes plasma instability. However, dilution of the samples would degrade detection limits, so the ability to directly analyze 20% NH4OH is important. The Agilent 7700s/7900 ICP-MS employs a unique, high-speed frequency-matching ICP RF generator that can maintain a stable plasma even when 20% NH4OH is aspirated. The 7700s/7900 also features effective technologies for removing spectral interferences in high-purity chemicals, making it ideally suited to semiconductor chemical analysis. An Agilent 7700s, using an inert sample introduction system, was used to measure trace elements in high purity 20% NH4OH. Detection limits in the single digit ppt or sub-ppt range were obtained for 48 elements, and long term (~7 hours) stability of approximately 5% RSD was achieved for a spike level of 100 ppt in 20% NH4OH, demonstrating the ability of the 7700s to routinely measure trace contaminants in high purity 20% NH4OH. Direct Measurement of Metallic Impurities in 20% Ammonium Hydroxide by 7700s/7900 ICP-MS