A Comparison of ICP-OES and ICP-MS for Trace Impurity Analysis in High-Purity Copper ALD Precursors

Advanced ALD (atomic layer deposition) precursors are designed to deposit thin films that must be reliable, clean and free of contaminants. This created a need for analytical methods to measure contaminants and ensure the purity of the starting compounds used in ALD. However, accurate analysis of multiple trace impurity elements in high purity copper precursors is extremely challenging. The paper presents a comparison of analytical performances of the inductively coupled plasma optical emission spectrometry (ICP-OES) and the inductively coupled plasma mass spectrometry (ICP-MS) for the trace analysis of copper(II) acetylacetonate. A detailed study of the copper matrix effect and its influence on the intensity of the analytical signals was performed. The limits of detection for ICP-OES and ICP-MS analysis ranged from 0.1 to 100 ng g^-1 for more than 60 trace elements. The capabilities of the ICP-MS technique were expanded by the use of a reaction/collision cell. The combination of the developed ICP-OES and ICP-MS methods allows monitoring 62 impurities in copper(II) acetylacetonate with a purity of 6N (99.9999 wt%). The accuracy was rigorously validated through spike recovery experiments and the analysis of a high-purity copper certified reference materials, demonstrating the absence of significant systematic errors. The methodology's applicability was further confirmed by analyzing additional copper precursors, showcasing its utility for quality control of copper ALD materials.