Determination of Argon in RF Sputtered SiO₂ by X-Ray Emission

Abstract

Argon is commonly used as the sputtering medium for RF sputtering of insulators and is entrapped in the deposits. X-ray emission determination of argon in RF sputtered SiO2 was required as part of a study of the relationships between argon concentration in the deposits and their electrical and physical properties.Concentrations ranging from 0.05 to 7.4 weight % argon were measured in deposits 0.5 to 5μ thick. Two techniques were used for standardization: (1) weight loss of deposits heated for several hours in a helium atmosphere at 600°C; (2) potassium Kα and chlorine Kα measurements on a KCl film of known thickness to infer argon mass/argon Kα net counts. Calibrations made using these procedures agreed to within 10% and are reliable to about ±25% on an absolute basis. Absorption of radiation by the deposits was taken into account and used to correct measured argon intensities for absorption.Sputtering parameters which had major effects on argon concentration were the substrate temperature and the magnetic field applied during sputtering. Argon pressure and RF power were found to have lesser effects.

X-ray absorption and emission

“…Concentrations of argon from 0.05 to 7.4 weight percent were determined in deposits 0.5 to 5 µ thick. Two techniques were used for calibration: weight loss of deposits heated at 600°C in a helium atmosphere for several hours and the use of a KC1 film for estimating the argon intensity-mass relationship (311).…”