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

We have demonstrated stacked HfSiON gate dielectrics with a low-Hf-concentration [Hf/(Hf + 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-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 (V-O(2+)) formation related to carrier traps. These results were supported by the results of first-principles calculation.