Sampling and real-time methods in electro-optic probing system [LSI testing]

Sampling and real-time methods in electro-optic (EO) probing systems using a laser diode (LD) for measuring the voltage waveform at internal nodes of the high-speed LSI are described, comparing performance to other electric instruments. The voltage sensitivity was improved by using an external ZnTe E-O probe and a low-noise LD. A sampling system using a pulsed LD has a frequency bandwidth of 10 GHz and a minimum detectable voltage of 430 μV/√Hz. The corresponding values for a real-time system using a CW LD and a high-speed photodetector are 480 MHz and 23 mV with 700 accumulations. Each system is based on a mechanical prober and a microscope. The advantages of a high temporal resolution, noncontact and noninvasive method are demonstrated during various measurements in several different areas: standing waves on a stripline, ring resonator and voltage waveform characteristics in a high-speed MMIC by the sampling method, long logic pattern signal, voltage waveforms at internal nodes in an ECL IC and those of a transport electrode in CCD by the real-time method