Preparation of high quality ultra-thin gate dielectrics by CAT-CVD and catalytic anneal

This paper reports a feasibility of Cat-CVD system for improvement in characteristics of ultra thin gate dielectrics. Particularly, the effects of post deposition catalytic anneal (Cat-anneal) by using hydrogen (H-2)-decomposed species or NH3-decomposed species produced by catalytic cracking of H-2 or NH3, are investigated. The C-V characteristics are measured by MIS diode for the 4.5nm-thick Cat-CVD SiNx and 8nm-thick sputtered SiO2 for comparison. The small hysteresis loop is seen in the C-V curve of both SiNx and SiO2 films as deposition. However, it is improved by the Cat-anneal using H-2 or NH3, and the hysteresis loop completely disappears from the C-V curves for both films. This result demonstrates that the Cat-anneal is a powerful technique to improve quality of insulating films, such as Cat-CVD SiNx and even sputtered SiO2 films. In addition, the leakage current of SiNx films with 2.8nm equivalent oxide thickness is decreased by several orders of magnitude than that of the conventional thermal SiO2 of similar EOT and the breakdown field is increased several MV/cm by Cat-anneal at 300 degrees C.