Review of Micro- and Nanoprobe Metrology for Direct Electrical Measurements on Product Wafers

At the nanoscale, the electrical resistivity of solids is strongly and nonlinearly affected by their chemistry, crystallography, and geometry (e.g., critical dimensions). To achieve on-spec performance of semiconductor devices, an exceptional process control is thus essential. Four-terminal sensing is a well-established electric metrology, where resistivity is obtained from applying a known current across one pair of electrodes in contact with the sample, while measuring the voltage drop across another. Thanks to microfabrication, the downscaled Micro Four-Point Probes (M4PP) are characterized by (sub-)µm inter-electrode spacing, which enables to accurately determine resistivity on comparable length scales, while reducing the risk of current leakage through adjacent layers/devices. In addition to electrical resistivity (typically determined at a <0.1% precision), other key transport parameters can often be concurrently quantified (e.g., Hall carrier density and mobility, the temperature coefficient of resistance, and certain thermoelectric parameters). Here, we review milestones in M4PP development, showcase its characteristic use for in-line process monitoring of product wafers, and flag recent methodological improvements and advances.