Formation of silicon nitride gate dielectric films at 300 °C employing radical chemical vapor deposition

Silicon nitride $({\mathrm{SiN}}_x)$ ultrathin gate dielectric films for ultralarge-scale integrated circuits have been successfully formed by radical chemical vapor deposition (R-CVD) at 300 °C. In this process, charged species incident on the silicon (Si) substrate during the growth were eliminated with the magnetic field in electron cyclotron resonance plasma-enhanced CVD employing nitrogen and silane $({\mathrm{N}}_{\mathrm{2}}{\mathrm{/SiH}}_4)$ gases. By using R-CVD, ${\mathrm{SiN}}_x$ films with very low leakage current and near-ideal dielectric constant (ε=7.2) have been obtained. In situ Fourier transform infrared reflection absorption spectroscopy (FT-IR RAS) has confirmed that the Si–N bonds are increased and the voids in films are reduced by eliminating charged species. A key factor for forming ultrathin ${\mathrm{SiN}}_x$ films of high quality at 300 °C is discussed, based on characterization of films synthesized with and without charged species on the substrate using in situ x-ray photoelectron spectroscopy, in situ FT-IR RAS, and in situ atomic force microscopy.