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

Abstract

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 ( $\rho _{C}$ ). $\rho _{C}$ of the ICP + RTA-treated Ti ohmic contacts decreased to lower than $10^{-{5}} \,\,\Omega \cdot \text {cm}^{{2}}$ after 400 °C postmetal deposition annealing (PMDA). However, the additional O atoms, fixed in the amorphous layer by RTA, affected the $\rho _{C}$ reduction. 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 $\rho _{C}$ , $1.3\times 10^{-{6}} \,\,\Omega \cdot \text {cm}^{{2}}$ , after 600 °C PMDA. The lowest $\rho _{C}$ is $25\times $ and $8\times $ lower than that of the Ni silicide and the nontreated Ti contacts, respectively, at the same doping concentration.