PRIMARY ELECTRON PULSE-SHAPE EVALUATION IN AN ABT SYSTEM

The time resolution of an electron beam testing system (EBT) is mainly related to the primary electron (PE) sampling pulse width. Signal dec onvolution techniques are available to enhance the time resolution of the system, provided the PE pulse shape is known with high accuracy. W hile for high energies this shape has already been evaluated, for the low energies commonly used in MOS IC testing, some additional difficul ties must be accounted for, such as increased PE beam spot dispersion, charge trapping into passivation oxides, and lower SIN ratio at the d etector. Here, we describe the direct measurement of the PE current us ed to sample internal voltage waveforms through the use of a fast aval anche photodiode. A numerical simulation has also been performed to he lp in the correct interpretation of the results. Using a known signal as an input to a matched-impedance microstrip line, a numerical deconv olution technique has been applied to the signal sampled by finite-dur ation current pulses to evaluate the goodness of the restoration of th e original signal.