Soichi Hama

Ultrafast-ultrafine probing of high-speed electrical waveforms using a scanning force microscope with photoconductive gating

Picosecond photoconductivity in low-temperature-grown GaAs (LT GaAs) has been used to provide temporal resolution both in rigid probes and in scanning force microscope probes. This article reviews the fabrication and use of such probes. 2.5 ps temporal resolution and few microvolts sensitivity are obtained at arbitrary points on circuits with a spatial definition of 100 nm. Rigid probes are tested in application to analogue and digital circuits. As an alternative to electron beam testing, scanning force probes are applied toin situ imaging and waveform measurement. Finally, the use of time-resolved waveform analysis with scanning-force microscopy probes with semiconductor laser sources is demonstrated.

Electron Beam (EB) delay tester

Abstract We have developed an EB delay tester for high-speed, high-accuracy measurement of the delay time between I/O pins of LSIs. In order to replace the measured LSI in the air, the LSI is placed on a multilayer board and measurement terminals on the back of the board are put in vacuum. For high-speed and high-accuracy measurement, we made an EB column with a large EB current of 100 nA and designed measuring technique based on binary search and feedback. The parameters of all measurement terminals are registered in advance to compensate position-dependence of the s-curve. Because these parameters are affected by EB current and vary over time, they are calibrated just before the edge timing measurement. Its measuring time is 168 ms and measurement accuracy is 56 ps when specified time resolution is 50 ps and repetition rate is 2.5 MHz.

Optical delay tester

The authors have developed an optical delay tester based on electro-optic sampling, and designed a prototype to test the timing of high-speed IC chips. The device puts an electro-optic crystal in contact with the terminals to be tested and measures the voltage waveform applied to the crystal. Measurement precision is 100 mV or better and timing precision measurement is 50 ps.