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

Hafnium nitride HfN"x was deposited for gate metal electrode application by MOCVD method using Hf[N(C"2H"5)"2]"4 (TDEAHf) precursor. Film composition and electrical resistance were analyzed by XPS and four-point probe technique. As a result, NH"3 gas, as reactant, plays an important role to the film characteristics. With respect to the growth with NH"3 gas, HfN"x 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 @W/@?, irrespective of NH"3 partial pressure and growth temperature. This was attributed to the formation of N-rich nitride, e.g., Hf"3N"4 component, which possesses high resistivity. On the other hand, by means of NH"3-free growth, metallic films containing about 30% of carbon were directly synthesized. The resistivity was in the range of 104 @m@W-cm at the deposition temperature of 700 oC by NH"3-free growth.