Electrical characterization of high-k gate dielectrics on Ge with HfGeN and GeO2 interlayers

Two kinds of HfSiOx/interlayers (ILs)/Ge gate stack structures with HfGeN- and GeO2-ILs were fabricated using electron cyclotron resonance (ECR) plasma sputtering and the subsequent post deposition annealing (PDA). It was found that HfGe was formed by the deposition of Hf metal on Ge and changed to HfGeN by N2 ECR-plasma irradiation, which was used as IL. Another IL was GeO2, which was grown by thermal oxidation at 500 °C. For dielectrics with HfGeN-IL, PDA of 550 °C resulted in effective oxide thickness (EOT) of 2.2 nm, hysteresis of 0.1 V, and interface state density (Dit) = 7 × 1012 cm− 2 eV− 1. For dielectrics with GeO2-IL, PDA of 500 °C resulted in EOT of 2.8 nm, hysteresis of 0.1 V, and Dit = 1 × 1012 cm− 2 eV− 1. The structural change of HfSiOx/GeO2/Ge during the PDA was clarified by using X-ray photoelectron spectroscopy, and the gate stack formation for obtaining the good IL was discussed.