Early stages of interface-trap transformation in metal-SiO2-(100)Si structures

Abstract

Interface traps and oxide charge generated by x ray and high-field Fowler–Nordheim (FN) injection are monitored within the first hour after their creation. A characteristic interface-trap peak distribution in the upper half of the Si band gap (∼Ev+0.75 eV) is invariably found immediately after x-ray irradiation or gate-positive FN injection. However, this peak distribution is not observed immediately after gate-negative FN injection; instead, it gradually develops with time after the injection, and is accompanied by a gradual reduction of the positive oxide charge density. In contrast, the interface-trap distribution after x ray or gate-positive FN injection undergoes much less notable changes within the first hour. In addition, the amount of damage measured immediately after FN injection depends strongly on the injection polarity, with gate-positive injection generating more interface traps and less positive charge while the reverse is true for gate-negative injection. These observations may be explained in terms of the differences in the initial trapped hole distribution and subsequent electron-hole interactions under different damage conditions.