Oxide-nitride-oxide capacitor reliability under heavy-ion irradiation

We investigate heavy ion irradiation effects on large area capacitors with an Oxide-Nitride-Oxide (ONO) stack as dielectric. Despite the thickness of this stack (16.5 nm), we observe the onset of a leakage current after irradiation. We demonstrate that this leakage current is a truly DC current that flows through the ONO stack and decreases with time. Electrical stresses demonstrate that irradiation does not reduce the time-to-breakdown of these devices. Noticeably, capacitors with a 9-nm SiO2 layer as dielectric and irradiated with the same ion specie and with the same fluence do not show any measurable leakage current.