Determination of chlorine in Hf precursors by high-resolution inductively coupled plasma mass spectrometry

Abstract

Chloride ions in Hf precursors used as insulators with a high dielectric constant in the semiconductor process were detected at the μg kg⁻¹ level by double-focusing sector field high resolution inductively coupled plasma mass spectrometry. A dilution method using a polar 1-methyl-2-pyrrolidinone solvent was applied because the Hf precursor reacts with moisture to form a precipitate. The Hf concentration in the Hf precursor was measured to check the measurement error. An appropriate dilution factor was determined by making a reference material with a concentration of 21–21 000 mg kg⁻¹ from the Hf precursor to confirm the appropriate concentration of Hf for the inductively coupled plasma mass spectrometry measurements. Chlorine ions in the Hf precursor were detected by preparing a calibration standard solution with a concentration of 9.98 mg kg⁻¹ from 2,4,6-trichlorophenol. A 100-fold dilution of the Hf precursor resulted in a limit of detection of 0.61 μg kg⁻¹, a limit of quantitation (LOQ) of 1.81 μg kg⁻¹, and a sample quantitation limit of 61 μg kg⁻¹. The concentration of chloride ions in the Hf precursor was below the LOQ, and the measurement result after spiking 10 μg kg⁻¹ to check the measurement reliability was 10.52 μg kg⁻¹, resulting in an accuracy of 95.60% and a precision of 3.58%. Finally, this method detected chlorine ions in a large number of samples in a short time without complicated pretreatment conditions and showed an excellent ability to detect all remaining chlorine, not limited to anionic substances, such as Cl⁻.