3-nm gap fabrication using gas phase sacrificial etching for quantum devices

We report nanometer-scale gap (nanogap) fabrication using gas-phase sacrificial layer etching. Sacrificial etching of 3-nm-thick sputtered Si films by XeF₂ gas was demonstrated for the first time. The same thick Si sacrificial layer was not etched by TMAH solution, and neither HF/CH₃OH vapor nor BHF solution etched a 3-nm-thick SiO₂ sacrificial layer. A nanogap formation by etching the 3-nm-thick Si sacrificial layer was ascertained by TEM observations. The underetch depth of a 3-nm gap reached 20 μm, which is large enough to use for quantum devices. The etching results were also found to reflect molecular behaviors.