Effects of Rapid Thermal Annealing on Ar Inductively Coupled Plasma-Treated n-Type 4H-SiC Schottky and Ohmic Contacts

The effects of Ar inductively coupled plasma (ICP) treatment followed by a 600 °C-1000 °C rapid thermal annealing (RTA) on the n-type 4H-silicon carbide (SiC) Schottky-barrier diodes and n⁺-implanted ohmic contacts were investigated. The ICP treatment created a 3-nm-thick, sp²-C-rich, and amorphous layer at the SiC surface. The RTA repaired the bombardment-induced damages before metal deposition to avoid current degradation. This ICP + RTA-treated surface strongly pinned the Schottky-barrier height (SBH) at a minimum of 0.88 eV. In theory, the low SBH is beneficial to decrease the specific contact resistance ( ρC). ρCof the ICP + RTA-treated Ti ohmic contacts decreased to lower than 10-5 Ω cm-2 after 400 °C postmetal deposition annealing (PMDA). However, the additional O atoms, fixed in the amorphous layer by RTA, affected the ρCreduction. Fortunately, due to the chemical affinity for O of Ti, the in-diffused Ti could contend for the O atoms against the Si-O bonds during the PMDA. Therefore, the oxidized barricade was decomposed gradually, leading to the lowest ρC, 1.3× 10-6Ω cm-2 , after 600 °C PMDA. The lowest ρCis 25× and 8× lower than that of the Ni silicide and the nontreated Ti contacts, respectively, at the same doping concentration.