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Linking mass measured by the quartz crystal microbalance to the SI

Published

Author(s)

Corey A. Stambaugh, Hamza Shakeel, Maritoni A. Litorja, Joshua M. Pomeroy

Abstract

The quartz crystal microbalance has been deployed across industry and academy for the monitoring of the film thickness during depositions. Over a half-a-century of academic and industrial research has gone into understanding the relation between film thickness and the corresponding frequency change of the loaded quartz crystal. However, a review of the literature shows that few experiments have examined the accuracy of the predicted mass change, and none appear to provide a direct link to the SI (International System of Units). Here, a vacuum metal deposition system is used to deposit films of Au of various masses on to the quartz crystals. The frequency change for several methods of frequency to mass conversion, none of which rely on the material properties of the deposited material, is compared to gravimetric based mass measurements using SI traceable mass artifacts; a complete uncertainty budget is provided. We find that when the energy-based method for frequency to mass conversion is applied, the calculated mass is within $0.36\;\%$, of the known value over most of the measured range. Only for mass changes below 100 $\mu \rm{g}$, where the uncertainty is the largest, are deviations from this result observed.
Citation
Metrologia
Volume
57
Issue
2

Keywords

qcm, quartz crystal microbalance, mass, thin film
Created February 12, 2020, Updated February 13, 2020