Determination of Trace Impurity Elements in Ultra-High Purity Copper Sputtering Targets by Glow Discharge Mass Spectrometry and Evaluation of Their Relative Sensitivity Factors

Glow discharge mass spectrometry (GDMS) was proposed for the determination of 39 trace impurity elements in ultra-high purity copper sputtering targets by selecting appropriate isotopes and resolution. The parameters in the glow discharge process were optimized, and the conditions were as follows:the discharge gas flow rate at 450 mL·min^-1, the discharge current of 2.00 mA, and the pre-sputtering time of 20 min. Because the GDMS standard sample of high purity copper was extremely difficult to get, in order to improve the detection accuracy of trace impurity elements, under the existing standard sample conditions, only the relative sensitivity factors (RSF) of 21 impurity elements matching the matrix were obtained by using the high purity copper standard sample, and those of the remaining 18 impurity elements could only be calculated according to standard RSF of the instrument. The detection limits of 33 impurity elements were calculated according to the second method in type III of American Society for Testing and Materials Standard ASTM F1593-08(2016), while the detection limits of the other six major impurity elements could not be obtained by this method because their contents were higher than the noise level of the instrument. The sputtering target samples of ultra-high purity copper were detected by GDMS. The main impurity elements were Si, P, S, Cl, Fe, and Ag, with the detection amounts in the range of 0.015-0.082 μg·g^-1, and the total amount of impurities was less than 1 μg·g^-1. The detection limits of Zn, Te, and Au were on level of 10 ng·g^-1, while the detection limits of other elements could reach ng·g^-1 level, and the detection limits of Th and U were even up to 0.1 ng·g^-1 level. It was shown that the method could fulfill the detection requirements of 6N (99.999 9%) ultra-high purity copper sputtering targets in GB/T 26017-2010.