Comparison of the structural properties and electrical characteristics of Pr₂O₃, Nd₂O₃ and Er ₂O₃ charge trapping layer memories

The structural properties and electrical characteristics of metal-oxide-high-fc material-oxidesilicon (MOHOS)-type memory devices using praseodymium oxide (Pr₂O₃), neodymium oxide (Nd ₂O₃) and erbium oxide (Er₂O₃) films as the charge storage layer were investigated. X-ray diffraction, atomic force microscopy and x-ray photoelectron spectroscopy were employed to analyze the structural and morphological features of these high-k films. It was found that MOHOS-type memory devices prepared under the Nd203 film and annealed at 800 °C exhibited a larger flatband voltage shift of 3 V (Vg = 10 V for 1 ms) and a lower charge loss of ~11% at room temperature as compared to other conditions. This result suggests that the Nd₂O₃ film having a rougher surface, higher ratio of silicate to silica and larger conduction band offset causes the higher probability for trapping the charge carrier and the deep electron trap level in the film.