Abstract

As complementary metal oxide semiconductor (CMOS) devices continue to scale along the rapid performance and miniaturization pace of Moore's Law, the unacceptably high direct tunneling leakage current through the thin transistor gate insulator layer is of increasing concern. To this end, gate insulator materials with significantly higher dielectric constants (k=10–25) continue to be investigated as potential replacements for silicon dioxide, SiO₂ (k=3.9), and silicon oxynitride. This challenge provides opportunities for integration of a physically thicker film with lower leakage current and with capacitance equivalent to <1.0 nm SiO₂. Local changes in the composition of the candidate material, uncapped metal–organic chemical vapor deposited (MOCVD) hafnium silicate, (HfO₂)_x-1(SiO₂)_x, have been evaluated by several techniques, including grazing incidence X-ray diffraction (GI-XRD), time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Hafnium silicate gate dielectric transistor performance data comparing high-k films with post-deposition anneal (PDA) treatments of NH₃ and N₂ at various process temperatures are presented. Changes in the material microstructure associated with phase segregation and crystallization as a function of Hf silicate composition and anneal temperature have been observed and discussions of the corresponding reaction mechanisms are presented.

Author Keywords: Hafnium silicate; Thermal response

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