Growth and characterization of HfOxNy gate insulators on Si(100).

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It was found that N incorporation in HfOxNy films improved the main drawbacks of HfO2, poor amorphous phase stability and high impurity diffusion rate, by inhibiting atomic diffusion in the films. Silicide formation at the Si/HfO0.61N0.26 interface was not observed following an anneal at 1000 °C in N2. This finding suggests that Hf or Si diffusion required for silicide formation at the interface was also suppressed by N in the HfOxNy film.HfO2 has been regarded as the most promising alternative film to replace SiO2 gate dielectric in sub-0.1 mum CMOS technology because of its acceptable dielectric properties and chemical stability. However, its poor amorphous phase stability and high impurity diffusion rate produce device reliability problems.In this work, ultra-thin stoichiometric HfOxNy gate dielectric films were deposited, for the first time, by pulse mode metal organic chemical vapor deposition (MOCVD) using the nitrogen incorporated precursor, tetrakis diethyl amido hafnium (TDEAH), [(C2H5 )2N]4Hf, and oxidant gas, NO. It was found that nitrogen in the high-k film was incorporated from both the precursor and NO gas, to as high as 9 at.% without any additional nitridation processes. The electronic band diagram structure of HfOxN y on Si(100) was determined, for the first time, by x-ray photoelectron spectroscopy (XPS). A valence band offset difference of 0.93 eV in HfO 0.61N0.26 and HfO2 was explained by the energy level difference (∼1.1 eV) of the N 2p and O 2 p density of states.HfOxNy gate dielectric films deposited with pulse mode MOCVD using TDEAH and NO showed equivalent electrical performances to those of HfO2 gate insulators with better thermal stability.Based on the C-V characteristics of the Al/HfO 0.61N0.26/Si(100) MOS capacitors, the dielectric constant of HfO0.61N0.26 was determined to be 17.5. The leakage current density for the HfO0.61N0.26 gate insulator with an EOT (Equivalent Oxide Thickness) of 2.5 nm was one and a half orders of magnitude lower than that for the SiO2 gate insulator with the same EOT and its tunneling current characteristics measured at T=77 K followed Folwer-Nordheim model. Device feasibility of HfO 0.61N0.26 gate dielectrics was demonstrated with n-channel MOSFETs with poly Si gates.

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