High quality of ultra-thin silicon oxynitride films formed by low-energy nitrogen implantation into silicon with additional plasma or thermal oxidation

Abstract

Silicon oxynitride (SiOxNy) insulators have been obtained by low-energy molecular nitrogen ion (N2+) implantation in Si substrates prior to thermal or high density O2 ECR (electron cyclotron resonance) or N2O RP (remote plasma) plasma oxidation at temperatures of 20°C and 350°C, respectively. Characterization by Fourier transform infrared (FTIR) analyses reveals the high structural quality and very low Si–N bond concentration of oxynitride films. The film thicknesses between 2.5 and 12 nm were found by ellipsometry using a fixed refractive index of 1.46. MOS capacitors, with Al electrodes and final sintering time at 420°C for 20–30 min in forming gas, were fabricated. A relative dielectric constant of 3.9 was adopted to extract the effective charge densities from capacitance–voltage (C–V) curves, resulting in values between 4×1010 and 6×1011 cm−2. Breakdown electric fields from 9–26 MV/cm were obtained from current–voltage (I–V) measurements. These results indicate that the obtained SiOxNy films are suitable gate insulators for metal-oxide-semiconductor (MOS) devices.