Method and apparatus for measuring time dependent signals with a particle probe

摘要

To measure high frequency signal curves at nodes and interconnections of integrated circuits and achieve a good chronological resolution in accordance with the sampling method, extremely short primary electron pulses are used. For such extremely short pulse widths obtainable with beam blanking systems, only individual statistically appearing secondary electrons are registered per pulse, these electrons generating current pulses having different amplitudes and different time behaviors at the output of an energy analyzer. It is proposed that the number of current pulses occurring at the output of the energy analyzer within a prescribed time interval be identified and the quotient, or ratio, thereof, be kept constant with the assistance of a feedback circuit for connection to the voltage of a retarding field electrode. The feedback circuit includes a pulse counter, a digital-to-analog converter, and a spectrometer drive.