A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

Abstract

Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (ΦBn,l) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured IF–VF–T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni2Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni2Si/4H-SiC Schottky contacts.

A Defects-Based Model on the Barrier Height Behavior in 3C-SiC-on-Si Schottky Barrier Diodes

“…It is reasonable to argue that the Schottky interface in SiC won't feature uniform properties in the lateral direction [63]- [68]. In the case of the investigated SBD, the small mismatch observed in the early forward bias stages in Fig.…”

Heavy Ion Induced Degradation in SiC Schottky Diodes: Bias and Energy Deposition Dependence

“…Schottky barrier engineering has been a topic of research for many years [4]- [8]. Annealing [6] and ion irradiation [7] have both been studied.…”

“…TCAD simulations also suggest that the degradation is associated with a thermal spike generated by the synergy of the heavy-ion strike and applied bias voltage, with higher bias resulting in higher peak lattice temperatures, similar to a Rapid Thermal Anneal (RTA) at the MetalSemiconductor interface. This RTA at the MetalSemiconductor interface may result in inhomogeneity of the Schottky barrier associated with the Ti/4H-SiC contact [4]- [8].…”

Enhanced Non-Uniformity Modeling of 4H-SiC Schottky Diode Characteristics Over Wide High Temperature and Forward Bias Ranges

“…In order to offer an application-oriented solution for modeling high-temperature-capable Schottky diodes, we've also introduced a model based on the well-established parallel conduction macroscopic concept which assumes current flow through discrete diode-patches. It successfully fitted the exponential portion of inhomogeneous Schottky diodes' forward behavior over wide ranges [3], [4]. A comparative evaluation of this model and the Gaussian distribution approach was presented in [16], proving the former's adequacy for wide-temperature-range characterization.…”

“…As such, m is considered the lowest number of regions on the contact surface, with different Schottky barrier heights, which is sufficient to account for most of the non-uniform device's forward current. Specifically, p eff,i indicates how much the area of diode i deviates from A S [3], [4], with higher values corresponding to smaller surfaces. Therefore, diodes with high p eff can only contribute significant current if their specific barrier height is low.…”