Film properties of nitrogen-doped polycrystalline silicon for advanced gate material

Deposition of N-doped poly-Si films from SiH4 and NH3 using a single wafer type low pressure chemical vapor deposition (LPCVD) system was investigated to improve the grain size reduction and the grain size distribution. The deposition rate and surface roughness of N-doped Si were greatly affected by the NH3/SiH4 ratio such that they decreased with increasing NH3/SiH4 ratio. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements revealed that with increasing NH3/SiH4 ratio, the size of the grains was decreased and the grains size distribution became uniform. Finally, we successfully obtained N-doped poly-Si films having uniform grain size of approximately 6 nm.