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

The feasibility of using ultrathin silicon nitride $(SiNx)$ 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 $(H2)$-decomposed species or $NH3$-decomposed species formed by catalytic cracking of $H2$ and $NH3$ are also studied. A small hysteresis loop is seen in the $C–V$ curve of as-deposited Cat-CVD $SiNx$ 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 $SiO2$ films of similar EOT. However, it is found that the properties of Cat-CVD $SiNx$ films are markedly improved by the postdeposition $H2$ or $NH3$ treatments, that is, the hysteresis loop disappears and the leakage current decreases by three orders of magnitude.