Al₂O₃/InGaAs Metal-Oxide-Semiconductor Interface Properties: Impact of Gd₂O₃and Sc₂O₃Interfacial Layers by Atomic Layer Deposition

Abstract

The use of InGaAs as a high carrier mobility CMOS-channel material requires a proper electrical passivation of its interface with the gate dielectric. We investigate InGaAs passivation by Atomic Layer Deposition (ALD) of Al2O3, Gd2O3, and Sc2O3 using tri-methylaluminum (TMA), (iPrCp)3Gd, (MeCp)3Sc, and H2O as precursors. We discuss the impact of the starting precursor and TMA exposure during the initial cycles of Al2O3 on the interface trap density (Dit), frequency dispersion, leakage current, and breakdown field. Increasing the TMA pulse time to five seconds during the first five cycles reduce the Dit to 1.8 × 1012 eV−1 cm−2, while frequency dispersion, leakage current and breakdown field generally improve. Gd2O3 and Sc2O3 interfacial layers between InGaAs and Al2O3 are examined. The initial growth study of Gd2O3 ALD on InGaAs indicates growth inhibition as compared to the hydrophilic SiO2/Si substrate. Gd2O3 and Sc2O3 improve the interface in terms of Dit and border traps. The improvement depends on the initial precursor pulse lengths, and on the Gd- or Sc-content. The lowest Dit values, 2.5 × 1012 eV−1 cm−2 and 1.8 × 1012 eV−1 cm−2, are obtained for four cycles of Sc2O3 and Gd2O3, respectively. Interfacial self-cleaning by TMA, (iPrCp)3Gd, and (MeCp)3Sc is demonstrated by X-ray Photo-electron Spectroscopy and Time-of-flight secondary ion mass Spectroscopy.