Gated-pulse stroboscopy for passivated device imaging

Charging effects in stroboscopic voltage contrast imaging of passivated devices may be reduced by pulsing the electron beam many times during each repetition of the test vector sequence. Signal pulses representing a single timing state are then separated from the others by sample-and-hold gating techniques. The multiple beam pulses during all portions of the test sequence produce a stable average surface charge which prevents fading of image contrast, permitting viewing of the image for extended periods. Results and comparisons with standard stroboscopy and low frequency sample-and-hold imaging are presented.