Ultrathin silicon nitride gate dielectrics prepared by catalytic chemical vapor deposition at low temperatures

The feasibility of using ultrathin silicon nitride (SiN_x) films, prepared by catalytic chemical vapor deposition (Cat-CVD) method, as an ultrathin gate dielectric is reported. The effects of postdeposition treatments carried out using hydrogen (H_2)-decomposed species or NH3-decomposed species formed by catalytic cracking of H_2 and NH_3 are also studied. A small hysteresis loop is seen in the C-V curve of as-deposited Cat-CVD SiN_x films. The leakage current in the case of these films with equivalent oxide thickness (EOT) of 3 nm is slightly larger than that in the conventional thermal SiO_2 films of similar EOT. However, it is found that the properties of Cat-CVD SiN_x films are markedly improved by the postdeposition H_2 or NH_3 treatments, that is, the hysteresis loop disappears and the leakage current decreases by three orders of magnitude