A NONINVASIVE OPTICAL PROBE FOR DETECTING ELECTRICAL SIGNALS IN SILICON INTEGRATED CIRCUITS

As the bandwidth of silicon integrated circuits is pushed towards microwave frequencies, electrical measurements inside these circuits become more difficult to make. The best commercially available noncontact probing technique, the voltage contrast scanning electron microscope (SEM), is complex, and has a low sensitivity. Present optical probing techniques are less complex than the SEM but still produce weak signals. Probing systems based on silicon's nonlinear optical interactions produce even smaller signals than the SEM, since the electrooptic interactions in silicon are weak.;In the future this probing system has the potential of simplifying complex microwave test systems, and since active devices in all semiconductor materials operate on the principle of charge control, we should be able to detect signals in IC's fabricated in any semiconductor material including GaAs, InGaAsP, Ge, and Si. In addition, because of the high spatial and temporal resolution capabilities of this system, we should be able to directly observe free-carrier dynamics in active devices. Finally, by optimizing a device which exploits the charge-optical interaction, we should be able to develop efficient integrated modulators for use in optical communication systems.;However, free carriers in an integrated active device introduce a significant perturbation in the index of refraction of the material. We have demonstrated a noninvasive 1.3...