A Study on the Temperature of Ohmic Contact to p-Type SiC Based on Ti₃SiC₂Phase

Abstract

In this paper, the electrical properties of Ti 3 SiC 2 -based ohmic contacts formed on p-type 4H-SiC were studied. The growth of Ti 3 SiC 2 thin films were studied onto 4H-SiC substrates by thermal annealing of Ti-Al layers deposited by magnetron sputtering. In this study, we varied the concentrations of Ti and Al (Ti 20 Al 80 , Ti 30 Al 70 , Ti 50 Al 50 , and Ti), and the annealing temperature from 900°C to 1200°C for each concentration. X-ray diffraction and transmission electron microscopy analyzes were performed on the samples to determine the microstructure of the annealed layers and to further investigate the compounds formed after annealing. Using the transfer length method structures, the specific contact resistance (SCR) at room temperature of all contacts was measured. The temperature dependence up to 600°C of the SCR of the best contacts was studied to understand the current mechanisms at the Ti 3 SiC 2 /SiC interface. The experimental results are in agreement with the thermionic field emission theory. With this model, the barrier height of the contact varies between 0.71 and 0.85 eV. Finally, ageing tests showed that Ti3SiC2-based contacts were stable and reliable up to 400 h at 600°C under Ar.Index Terms-Ohmic contact, silicon carbide (SiC), thermionic field emission (TFE), Ti-Al alloy, Ti 3 SiC 2 .

Ohmic Contacts on p-Type Al-Implanted 4H-SiC Layers after Different Post-Implantation Annealings

“…From Table 2, it is interesting to note that Frazzetto et al [17] obtained a lower Φ B of 0.46 eV using Ti/Al contacts. The lowering of the barrier has been attributed to the formation of the ternary phase Ti 3 SiC 2 [19,20,21]. A slightly higher barrier height of 0.56 eV has been reported by Vivona et al [25] for Ti/Al/Ni contacts (similar to our samples).…”

“…Other literature works described the carrier transport for Ti/Al-based contacts with the TFE model [17,19,21,24,25]. From the fit of the specific contact resistance, different values of barrier height have been obtained (see Table 2).…”

“…These systems can give promising values of specific contact resistance ρ c , in the range 10 −4 –10 −5 Ω cm 2 [17,18]. Hence, they have been the object of several investigations aimed at understanding the role of the interface microstructure on the transition from a Schottky to an Ohmic behavior [19,20,21]. Recently, alternative solutions employing protective capping layers on Ti/Al stacks (Si [22], NiV [23], W [24], Ni [25]) or Ni-Ti-Al systems [26,27,28,29] have been proposed to limit surface degradation upon annealing and to improve the contact reliability.…”

Ti/Al-based contacts to p-type SiC and GaN for power device applications

“…Here, it is worth noting that other recent works on Ti/Al‐based systems reported similar observations, with a specific contact resistance ρ c decreasing with the temperature according to the dominant carrier transport mechanism in the system. The comparison with these works corroborates our interpretation, i.e., the temperature dependence of ρ c may depend on the interfacial contact microstructure, which in turn is determined by the initial composition of the Ti/Al‐based stack .…”

“…Several works have been reported on p‐type doped SiC, where metal layers based on Ti and Al are typically subjected to thermal treatments above 800 °C in order to obtain Ohmic contacts . In the contact formation, the role of the Ti 3 SiC 2 phase is continuously under discussion . However, these Al‐containing systems exhibit often of a poor morphology due to the tendency of Al to ball‐up during annealing .…”