We have investigated the correlation between the microwave loss andpatterning method for coplanar waveguide titanium nitride resonators fabricatedon Si wafers. Three different methods were investigated: fluorine- andchlorine-based reactive ion etches and an argon-ion mill. At high microwaveprobe powers the reactive etched resonators showed low internal loss, whereasthe ion-milled samples showed dramatically higher loss. At single-photon powerswe found that the fluorine-etched resonators exhibited substantially lower lossthan the chlorine-etched ones. We interpret the results by use of numericallycalculated filling factors and find that the silicon surface exhibits a higherloss when chlorine-etched than when fluorine-etched. We also find frommicroscopy that re-deposition of silicon onto the photoresist and side walls isthe probable cause for the high loss observed for the ion-milled resonators
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