Focused Ion Beam Induced Effects on MOS Transistor Parameters

Abstract

We report on recent studies of the effects of 50 keV focused ion beam (FIB) exposure on MOS transistors. We demonstrate that the changes in transistor parameters (such as threshold voltage, Vt) are essentially the same for exposure to a Ga+ ion beam at 30 and 50 keV under the same exposure conditions. We characterize the effects of FIB exposure on test transistors fabricated in both 0.5 μm and 0.225 μm technologies from two different vendors. We report on the effectiveness of overlying metal layers in screening MOS transistors from FIB-induced damage and examine the importance of ion dose rate and the physical dimensions of the exposed area.

Charge Neutralization Using Focused 500 eV Electron Beam in Focused Ion Beam System

“…This charge-induced high voltage causes Fowler-Nordheim tunneling through a gate oxide, and tunneling electrons and holes generate oxide-and interface-trapped charges, which induce a change in transistor parameters. A charge neutralization technique using an electron shower 2,4) has been reported. However, even with the electron shower, it is not easy to prevent changes in transistor parameters induced by FIB irradiation, and the electron shower causes parameter shifts of transistors located outside the FIB irradiation area.…”

Antistatic Technique for Suppressing Charging in Focused Ion Beam Systems Using Microprobing and Ion-Beam-Assisted Deposition

“…The hot carriers generate oxide-and interface-trapped charges and induce a change in the transistor parameters. To suppress FIB-induced charging phenomena, antistatic techniques such as a method of overcoating a thin conductive layer 4) and a method using an electron shower 2,5) have been used for many years. However, conductive layer coating is not a convenient method because the conductive layer must be removed after FIB exposure.…”