Enhanced initial growth of atomic-layer-deposited metal oxides on hydrogen-terminated silicon Appl. Phys. Lett. 83, 740 (2003); 10.1063/1.1595719 Ultrathin nitrided-nanolaminate ( Al 2 O 3 / ZrO 2 / Al 2 O 3 ) for metal-oxide-semiconductor gate dielectric applications J.

Hf O 2 growth on H-terminated Si surfaces by atomic layer deposition (ALD) is studied with in situ Fourier transform infrared spectroscopy and ex situ Rutherford backscattering, using tetrakis-(ethyl-methyl-amino) hafnium and ozone as the hafnium and oxygen precursors, and compared to water-vapor-based ALD growth. The reaction pathways are different for the two oxygen precursors, leading to a lower growth rate for ozone (∼0.05nm∕cycle) than for water-based growth and to incorporation of different impurities in the HfO2 film. Furthermore, interfacial SiO2 is readily formed with ozone at the growth temperature (∼100°C), in contrast to water-based HfO2 growth.

Growth at moderate temperatures, below ϳ100°C, is shown to prevent interfacial silicon oxidation during atomic layer deposition of high-permittivity ͑high-͒ gate dielectrics on hydrogen-terminated Si͑100͒. Trimethylaluminum, employed for aluminum oxide growth, leaves the hydrogen layer completely intact. Tetrakis͑ethylmethylamido͒hafnium partially scavenges the hydrogen layer during hafnium oxide nucleation, resulting in an interface composed of H-terminated silicon atoms and Si-O-Hf bridges. In both cases, high-dielectrics are grown without formation of interfacial SiO 2 . Once grown at low temperatures, subnanometer Al 2 O 3 layers effectively prevent interfacial SiO 2 formation during subsequent growth at higher temperatures required for optimum highquality. This two-step deposition scheme may thereby be useful for gate-stack scaling.

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The nature of the interface between Si and Ge substrates and high-k dielectrics often controls the performance of MOSFET devices. Precleaning and/or chemical functionalization of the surfaces can dramatically affect the formation of an interfacial layer. We have used in-situ IR spectroscopy to probe the relevant interfaces during ALD growth for a variety of surface treatments, including H- and Cl-termination, and nitridation. This paper focuses on understanding of the mechanisms for interfacial SiO2 (or GeOx) formation during HfO2 growth using tetrakis-ethylmethylamidohafnium (TEMAH) as the metal precursor and water or ozone as the oxygen precursor. We find that impurities arising from incomplete ligand elimination during growth (e.g. OH for H2O processing and CO- and NO-containing species for O3 processing) are incorporated into the HfO2 film during growth. Upon annealing, most of these species react, but can also migrate to the interface. Nitridation of Si and Ge surfaces will in general prevent SiO2 or GeOx formation but can also affect the growth rate.