Measurements of deep penetration of low-energy electrons into metal-oxide-semiconductor structure

A polycrystalline Si-SiO2-Si metal-oxide-semiconductor (MOS) transistor covered with thick insulation and passivation layers of SiO2 was examined to measure the threshold voltage shifts as a function of electron energy over the range of from 5 to 18 keV. The electron-beam fluence was varied over six orders of magnitude from 2×10−9 to 2×10−3 C/cm2. From the experimental data, the fraction of the incident electron energy deposited in the gate oxide was determined. The result shows a deep penetration of low-energy electrons beyond the electron range.