How the electro-optic probing system can contribute to LSI testing?

The electro-optic (E-O) probing system using laser diode (LD) for measuring the voltage waveform at internal nodes of high speed LSI is 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. Two kinds of E-O probing systems have been developed; a sampling system using a pulsed LD has the frequency bandwidth of 10 GHz and the minimum detectable voltage of 430 μV/√Hz, and a real time system using a CW LD and a high speed photo detector has 480 MHz and 23 mV with 700 accumulations. Each system is based on mechanical prober and a microscope. Approach of the E-O probe to the electrode is computer-controlled. The advantages of high temporal resolution, noncontact and noninvasive method have realized measurements for microwave devices and passivated electrodes. Dependency of the output signal on the space between E-O probe and electrode is discussed as well as that on the electrode width