Making Ultra-Low Current Measurements

Parametric characterization of semiconductor devices typically requires making extremely low current measurements. For example, in modern, highly integrated circuits, the off state current is typically on the order of just femtoamps. A typical semiconductor characterization system will include a DC characterization system, a switch matrix, a probe station, and cabling. Too often, however, when a semiconductor characterization system is configured, the system specifier will tend to concentrate on the DC parametric instrumentation while neglecting the rest of the system. This application note discusses several important aspects of making low current measurements, including grounding and shielding, noise in the measurement, and system settling time. ■