Ultrathin fluorinated silicon nitride gate dielectric films formed by remote plasma enhanced chemical vapor deposition employing NH3 and SiF4

Ultrathin fluorinated silicon nitride $({\mathrm{SiN}}_x)$ films of 4 nm in thickness were formed on a Si substrate at $\text{350\hspace{0.05em}°}\mathrm{C}$ in the downflow of electron cyclotron resonance plasma-enhanced chemical vapor deposition employing ammonia and tetrafluorosilane $({\mathrm{NH}}_{\mathrm{3}}{\mathrm{/SiF}}_{\mathrm{4}})$ gases. Ultrathin fluorinated ${\mathrm{SiN}}_x$ film was evaluated for use as a gate dielectric film. The observed properties indicated an extremely low leakage current, one order of magnitude lower than thermal ${\mathrm{SiO}}_{\mathrm{2}}$ of identical equivalent oxide thickness, as well as an excellent hysteresis loop (20 mV) and interface trap density ${\mathrm{(D}}_{\mathrm{it}}{\text{=4×10}}^{11} {\mathrm{cm}}^{\mathrm{-2}})$ in the capacitance–voltage characteristics. The film structures and the surface reactions for the fluorinated ${\mathrm{SiN}}_x$ film formation were examined via in situ x-ray photoelectron spectroscopy. in situ Fourier-transform infrared reflection absorption spectroscopy, in situ atomic force microscopy, and thermal desorption mass spectroscopy. The control of the fluorine concentration in the ${\mathrm{SiN}}_x$ films was found to be a key factor in the formation of fluorinated ${\mathrm{SiN}}_x$ films of high quality at low temperatures. Fluorinated ${\mathrm{SiN}}_x$ is the effective material for application in ultrathin gate dielectric film in ultralarge-scale integrated circuits.