Breakdown of gate oxides during irradiation with heavy ions

Breakdown of thin gate oxides from heavy ions is investigated using capacitor test structures. Soft breakdown was observed for 45 Angstrom oxides, but not for 75 Angstrom oxides. Lower critical fields were observed when experiments were done with high fluences during each successive step. This implies that oxide defects play an important role in breakdown from heavy ions and that breakdown occurs more readily when an ion strike occurs close to a defect site. Critical fields for 75 Angstrom oxides are low enough to allow gate rupture to occur at normal supply voltages for ions with high LET.