Effect of NH3 on the fabrication of HfN as gate-electrode using MOCVD

Hafnium nitride HfNx was deposited for gate metal electrode application by MOCVD method using Hf[N(C2H5)2]4 (TDEAHf) precursor. Film composition and electrical resistance were analyzed by XPS and four-point probe technique. As a result, NH3 gas, as reactant, plays an important role to the film characteristics. With respect to the growth with NH3 gas, HfNx films with low levels of carbon (< 0.1 at.%) and oxygen (∼ 2 at.%) impurities were formed. However, the resistance was very high and nearly over the measurable order of 108 Ω/□, irrespective of NH3 partial pressure and growth temperature. This was attributed to the formation of N-rich nitride, e.g., Hf3N4 component, which possesses high resistivity. On the other hand, by means of NH3-free growth, metallic films containing about 30% of carbon were directly synthesized. The resistivity was in the range of 104 μΩ-cm at the deposition temperature of 700 °C by NH3-free growth.