Influence of dielectric layer thickness on charge injection, accumulation and transport phenomena in thin silicon oxynitride layers: a nanoscale study

Abstract

Charge injection and retention in thin dielectric layers remain critical issues due to the great number of failure mechanisms they inflict. Achieving a better understanding and control of charge injection, trapping and transport phenomena in thin dielectric films is of high priority aiming at increasing lifetime and improving reliability of dielectric parts in electronic and electrical devices. Thermal silica is an excellent dielectric but for many of the current technological developments more flexible processes are required for synthesizing high quality dielectric materials such as amorphous silicon oxynitride layers using plasma methods. In this article, the studied dielectric layers are plasma deposited SiOxNy. Independently on the layer thickness, they are structurally identical: optically transparent, having the same refractive index, equal to the one of thermal silica. Influence of the dielectric film thickness on charging phenomena in such layers is investigated at nanoscale using Kelvin Probe Force Microscopy (KPFM) and Conductive Atomic Force Microscopy (C-AFM). The main effect of the dielectric film thickness variation concerns the charge flow in the layer during the charge injection step. According to the SiOxNy layer thickness two distinct trends of the measured surface potential and current are found, thus defining ultrathin (up to 15 nm thickness) and thin (15 nm-150 nm thickness) layers. Nevertheless, analyses of KPFM surface potential measurements associated with results from Finite Element Modelling of the structures show that the dielectric layer thickness has weak influence on the amount of injected charge and on the decay dynamics, meaning that pretty homogeneous layers can be processed. The charge penetration depth in such dielectric layers is evaluated to 10 nm regardless the dielectric thickness.

Nanoscale dielectric properties of TiO2 in SiO2 nanocomposite deposited by hybrid PECVD method

“…Concerning N = 1 NC films (black square symbol), both V m and FWHM are increasing correspondingly with the applied bias that is consistent with the behavior observed for SiO 2 films [8,38]. For N = 5 and N = 10 NC films, the same behavior as the one observed for N = 1 is obtained (i.e.…”

“…Moreover, the profile shape remains bell-like after charge injection (inset figure 6(d)). To fully understand such behavior, surface potential profiles were fitted with a Gaussian function to extract three parameters: (i) the maximum surface potential V m , (ii) the Full-Width at Half Maximum (FWHM) that represents the lateral charge spreading and (iii) the area under the potential peak A s that represents the charge density for a fixed thickness [38]. For each applied voltage, charge injection was carried out at three different locations on the film NC surface.…”

Comparison of TiₓSi1-x O2 mixed oxide and TiO₂ in SiO₂ nanocomposite dielectric properties at nanoscale

“…Results highlight that, for similar εr, NC films exhibits lower current density J than MO. In term of εr our films are similar to classical high-k material, however it is rather difficult to compare C-AFM current density to macroscale one as the surface collection in C-AFM is low, difficult to determine accurately [14] and does not permit to reach very low current density (i.e. lower than 10 -2 -10 -3 A.cm -2 ).…”

Determination of Type and Concentration of Traps in Nanoscale-Thick HfO2 Films Applicable for Gate Dielectric Stacks

“…Recently, scanning Kelvin probe microscopy has been actively used to study the local properties of dielectric layers. It is known to be used in studies of thin (5–100 nm) layers of dielectrics such as SiO 2 or SiO x N y as well as organic field-effect transistors . This method makes it possible to observe the process of charge dissipation in a layer at the microscopic level, to determine the parameters of traps, such as the content and activation energy, and also to separate the contribution of different types of traps to the conductivity.…”