Evidence of hafnia oxygen vacancy defects in MOCVD grown Hf_xSi_(1-x)O_y ultrathin gate dielectrics gated with Ru electrode

摘要

We studied the leakage current mechanism in Ru-gated MOS capacitors with ultrathin Hf_xSi_(1-x)O_y gate dielectrics grown by atomic vapour deposition (AVD~®). The dielectrics were annealed by rapid thermal annealing in oxygen atmosphere at temperatures ranging from 700 to 1000℃. Temperature dependent current-voltage characteristics exhibit trap-assisted tunneling through the Hf-silicate film annealed at 700℃. The energy trap level is 2 eV below the dielectric conduction band edge. On the other hand, direct tunneling was found to control the leakage current through gate dielectrics annealed at 800 and 900℃. Based on a microstructural study, the trap level was attributed to hafnia oxygen vacancies in the Hf-silicate.