Sub-10 nm-scale capacitors and tunnel junctions measurements by SMM coupled to RF interferometry

We have developed an adjustable Interferometer combined to a Scanning Microwave Microscopy (ISMM) to characterize the impedance of thousands of nanocapacitors. The adjustable interferometer allows the choice of the interference frequency within ± 50 MHz as well as the choice of the impedance range where the interference occurs. Calibration is investigated using metal-insulating-semiconductor capacitances. The ISMM allows quantitative characterization of tiny capacitors with size reaching sub-10 nm and capacitance value around the aF with a limit of resolution of about 0.5 aF at 7.8 GHz. A water meniscus parasitic capacitance is introduced to explain the discrepancy between measured and theoretical values over the 5 to 100-nm nanodot diameter range. The ISMM allows also measuring tunnel junctions made with very thin Al2O3 dielectric layers.