Laser stimulated electron-beam prober for 15 ps resolution internal waveform measurements of a 5 Gb/s ECL circuit

The use of an electron beam prober to characterize the internal signals of a high bandwidth crosspoint switch is discussed. Since the total delays through the switch amount to less than 1 ns, measurement of the stage-to-stage delays requires a prober with very high temporal resolution. The electron beam prober uses a pulsed laser photocathode to achieve very narrow electron pulses, with a much greater beam current than a thermionic cathode system. This instrument allows routine measurement of signals on submicron features with 15-ps resolution. Measurements of internal risetimes of 100 ps and stage-to-stage delays of less than 50 ps established the true internal switch setup time. Additional data were used to confirm that the internal biasing of the circuit was optimized.<>