Ultra-Low Noise Defect Probing Instrument for Defect Spectroscopy of MOS Transistors

It is commonly accepted that the performance and time-to-failure of modern semiconductor transistors are seriously affected by single defects located in the insulator or at the insulator/semiconductor interface. The impact of such single defects on the device current ranges from several pico-ampere up to hundreds of nano-ampere and their characterization poses a major challenge for measurement instruments. However, for an accurate description of the device behavior under operation, the understanding of the physical mechanism behind single-charge trapping is inevitable. For this a large variety of defects and devices with different geometries have to be studied. However, the impact of single defects on the device current rapidly decreases with increasing effective gate area. Thus, suitable measurement instruments have to provide a high current measurement resolution at a large signal-to-noise ratio (SNR) for monitoring single charge transitions. To enable defect spectroscopy at a very detailed level an ultra-low noise defect probing instrument (DPI) is invented. The compact implementation and optional usage of a lead battery supply unit for the DPI guarantees highest SNR and also long-term stability over more than two years, which is typically hard to achieve when instruments of different manufacturers are connected. Utilizing the DPI a measurement resolution of a few micro-volts in terms of threshold voltage shift can be achieved, which fairly outweighs the results obtained with general-purpose instruments.