Tunneling currents through ultrathin oxide/nitride dual layer gate dielectrics for advanced microelectronic devices

Abstract

Direct and Fowler-Nordheim tunneling currents through oxide and dual layer silicon oxide-silicon nitride dielectrics are investigated for substrate and gate injection. The calculations include depletion effects in the heavily doped (n ϩ) polysilicon gate electrodes as well as quantization effects in the less heavily doped n-type substrates. The Wentzel-Kramers-Brillouin ͑WKB͒ effective mass approximation has been compared with exact calculations for the tunneling probability, and based on these comparisons it has been found that the WKB approximation is adequate for single layer dielectrics, but is not for the dual layer dielectrics that are the focus of this article. Using exact tunneling transmission calculations, current-voltage (I-V) characteristics for ultrathin single layer oxides with different thicknesses ͑1.4, 2.0, and 2.3 nm͒ have been shown to agree well with recently reported experiments. Extensions of this approach demonstrate that direct tunneling currents in oxide/nitride structures with oxide equivalent thickness of 1.5 and 2.0 nm can be significantly lower than through single layer oxides of the same respective thickness.

Investigation of dependence between time-zero and time-dependent variability in high-κ NMOS transistors

“…We implemented the modified direct tunneling current for high-κ gate stack proposed in [31]. where, Φ B is the barrier height seen by the carriers in conduction band of the substrate and V SiO2 , t SiO2 , and T WKB are the voltage drop across the SiO 2 layer, thickness of the IL layer, and the tunneling probability across the dual gate stack determined using WKB approximation [24], respectively. The stress-induced current due to trap generation (TG) is modeled as [13] …”

“…In order to model the conditional probability P(C|G), we calculated the tunneling probability of electrons, P WKB by Wentzel-Kramers-Brillouin (WKB) method [24] and compared that with a set of pseudo-random probabilities P r .…”

Temperature effects on the electrical properties and structure of interfacial and bulk defects in Al/SiNx:H/Si devices

“…In this ultrathin range, boron transport from the p ϩ poly-Si gate electrode to the channel region occurs during the high temperature anneals that are required to activate the B dopant atoms. Additionally, direct and Fowler-Nordheim tunneling currents 6 become important and comparable to off-state drain currents. The higher dielectric constant of SiN x :H compared to SiO 2 allows increasing the physical thickness of the gate dielectric while retaining a low oxide equivalent thickness.…”

“…13 For ultrathin films with a low density of defects, Fowler-Nordheim and direct tunneling conduction have been observed. 6,13 The studies of the SiN x :H/Si interface have been performed mainly by capacitance-voltage (C -V) measurements, 12,14 from which the density of interface states can be calculated. [15][16][17] Much effort has been devoted to reduce this density of states to a level comparable to the Si/SiO 2 interface.…”

Origin and repartition of the oxide fixed charges generated by electrical stress in memory tunnel oxide

“…[1][2][3] However, it is well known that the electrical properties of MOS structures depend much on electrically active defects. In this work, we describe a method to determine the nonuniform dielectric fixed charge distribution induced by electrical stress of metal/SiO 2 /metal structures, based on the analysis of tunneling currents after electrical stress.…”