CHARGE COLLECTION FROM FOCUSED PICOSECOND LASER-PULSES

The magnitude of the charge collected in test structures following the passage of a heavy energetic ion was measured and compared with that generated by a picosecond pulse of laser light to determine whether pulsed lasers can substitute in some cases for the more expensive and time-consuming accelerators currently used for single-event-upset (SEU) testing of circuits. Two phenomena that are known to play a significant role in determining the magnitude of the collected charge generated by an ion beam - funneling and the shunt effect - were also observed for irradiation by a pulsed laser beam. The results show that the collected charge from laser irradiation was proportional to the 4/3 power of the laser energy for the case of funneling and to the 1.683 power of the laser energy for the shunt effect, in full agreement with results previously obtained for ion-beam irradiation. The proportionality constant for these CMOS devices was smaller by a factor of 6.5 for the laser-induced shunt experiments due to the much lower track charge density produced by the laser light. By correcting the laser data to take the lower charge density in the track into account, a good correlation between the ion and laser data was found, suggesting that the pulsed laser can be used to measure SEU sensitivity of integrated circuits.