Effect of poly silicon thickness on the formation of Ni-FUSI gate by using atomic layer deposited nickel film

The effect of poly-Si thickness on silicidation of Ni film was investigated by using X-ray diffraction, auger electron spectroscopy, cross-sectional scanning transmission electron microscopy, resistivity, I–V, and C–V measurements. The poly-Si films with various thickness of 30–200 nm were deposited by LPCVD on thermally grown 50 nm thick SiO2, followed by deposition of Ni film right after removing the native oxide. The Ni film was prepared by using atomic layer deposition with a N2-hydroxyhexafluoroisopropyl-N1 (Bis-Ni) precursor. Rapid thermal process was then applied for a formation of fully silicide (FUSI) gate at temperature of 500 °C in N2 ambient during 30 s. The resultant phase of Ni-silicide was strongly dependent on the thickness of poly-Si layer, continuously changing its phase from Ni-rich (Ni3Si2) to Si-rich (NiSi2) with increasing the thickness of the poly-Si layer, which is believed to be responsible for the observed flat band voltage shift, ΔVFB, in C–V curves.