Performance and Reliability Improvement of HfSiON Field-Effect Transistor with Low Hafnium Concentration Cap Layer Formed by Metal Organic Chemical Vapor Deposition with Diethylsilane

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We have demonstrated stacked HfSiON gate dielectrics with a low-Hf-concentration [$\text{Hf}/(\text{Hf}+\text{Si})=6$%] cap (LHC) layer. For fabricating the LHC layer, diethylsilane is more effective due to its decomposition characteristics being better than those of conventional amine-based precursors. The stacked structures exhibit improved mobility, the suppression of $V_{\text{th}}$ shift, superior negative bias temperature instability (NBTI), and positive bias temperature instability (PBTI) reliability for complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs), while maintaining low gate leakage currents. The mobility improvement is due to the superior control of nitrogen atoms, and the superior threshold voltage control and long-term reliability of the film are mainly due to the suppression of the positive oxygen vacancy (VO2+) formation related to carrier traps. These results were supported by the results of first-principles calculation.
2008-02-25