The impact of FIB on integrated circuits can be modeled as a positive charge (Ga(+)) accumulation on the passivation surface. High electrical fields across the oxide induce Fowler-Nordheim currents resulting in charge trapping in the oxide which in turn effects circuit parameters. MOS technologies are less sensitive to FIB operations than bipolar technologies because the gate of the MOS acts as an electrostatic shield. MOS transistors are relatively immune to FIB as long as they are grounded and after 2000 hours of burn-in all structures were functional with performance similar to the reference. FIB on future technologies is expected on one hand to benefit from the use of additional metal lines and power planes that protect active areas, and on the other hand, to be less protected by input diodes being less tolerant to the high voltage on transistor gates induced by FIB irradiation. These burn-in studies allowed the authors to give a positive answer to the question concerning the reliability of FIB modified devices. This also confirmed the experience the authors have at the CNES-Thales Lab. on different FIB modified circuits still in operation after several years. With UV (20 min.) and thermal annealing (150 deg C/24 hours), a majority of the degradation can be recovered. Device parameter drift is practically stabilized. The work shows that if the circuit characteristics are still within their specification it means that this FIB modified device should keep working for several years.
Reliability of integrated circuits modified by focused ion beam for space applications
Zuverlässigkeit von durch fokussierte Ionenstrahlbearbeitung modifizierten integrierten Schaltungen für die Raumfahrt
2002
10 Seiten, 14 Bilder, 2 Tabellen, 11 Quellen
Conference paper
English
Reliability of integrated circuits modified by focused ion beam for space applications
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