Effects of 6 MeV electron irradiation on the electrical properties and device parameters of Al/Al2O3/TiO2/n-Si MOS capacitors

The effects of 6 MeV electron irradiation on the electrical properties and device parameter characteristics of Al/Al2O3/TiO2/n-Si metal–oxide–semiconductor capacitors have been studied. Twelve Al/Al2O3/TiO2/n-Si MOS capacitors were fabricated using r.f. magnetron sputtering and divided into four groups. The first group was not irradiated and treated as virgin. The rest were irradiated with 6 MeV electrons at doses 10, 20, and 30 kGy, maintaining the dose rate at ∼1 kGy/min. Variations in crystallinity of the virgin and irradiated capacitors were studied using grazing incident X-ray diffraction. The thickness and in-depth elemental distributions of individual layers were determined using secondary ion mass apectrometry. Capacitance–voltage, conductance–voltage and leakage current–voltage characteristics of the virgin and irradiated samples were studied. The device parameters (flat band voltage, surface charge density and interface trap density of the virgin and irradiated structures) were determined. The electrical properties of the capacitors were investigated and the Poole–Frenkel coefficient of the capacitors was determined from leakage current measurements. The leakage current mechanism has been explained.

► The electron irradiation effects make variation in the device parameters.
► The device parameters changes due to percentage of defects and charge trapping.
► Leakage current of Al/Al2O3/TiO2/n-Si changes due to interface dangling bonds.
► The leakage current mechanism of MOS structures is due to Poole–Frenkel effect.