Ion beam modification of the dielectric properties of thin silicon dioxide films

The aim of this investigation was to understand the changes brought about in the dielectric properties of thin SiO₂ layers after exposure to ion beams. Oxidized silicon wafers were exposed to 16 keV Si ion beams. Subsequently, front and back metallizations were carried out to complete the MOS structures. The CV measurements revealed many interesting features. One of these was a hysteresis effect in the ion-exposed samples, whose magnitude and sign depended upon the ion dosage. Another interesting observation was the frequency dispersion of the accumulation capacitance at very low frequencies, caused by the formation of a pi junction in the heavily damaged silicon subsurface layer. Further, the oxide dielectric constant was found to increase at high ion dosages.