A laser-diode-based picosecond electrooptic prober for high-speedLSIs

An external electrooptic (EO) prober to diagnose high-speed LSIs is described. The prober employs a GaAs probe tip as a proximity electric field sensor and a semiconductor laser diode as an optical sampling pulse source. Polarization detection optics of the prober are compactly implemented in a specially designed electrooptic sampling (EOS) module. Accurate and reproducible measurement is achieved with the module and a precise EO probe positioner. The minimum detectable voltage is 16 mV/√Hz, which is sufficient to measure an emitter-coupled logic (ECL) level signal of less than 1 V. The temporal resolution is 24 ps, which is now limited by the optical sampling pulsewidth. The system is successfully applied to measure waveforms of internal nodes of gigahertz-band LSIs