Characterization of silicon nitride layers deposited in three-electrode plasma-enhanced CVD chamber

Abstract

Two series of amorphous silicon nitride films were deposited using a chemical vapour deposition (CVD) reactor with two and three electrodes. Nitrogen gas and silane diluted with argon mixture (5% SiH₄ + 95% Ar) were used as the working gas. The silicon nitride films were deposited at the same time on CaF₂ and aluminium-coated glass substrates at 300 °C. Changing of the injected gas ratios allowed us to shift the band gap of the films in the 1.85–5.15 eV range. From AFM analysis it was found that the samples deposited in a three-electrode chamber demonstrated lower surface roughness. The electrical measurements revealed that the samples deposited in the three-electrode CVD reactor demonstrated lower leakage current and higher breakdown voltage. The composition of layers was investigated using energy-dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopies. Additionally, the composition of the deposited films was evaluated from the refractive indexes, which have been estimated by fitting the spectroscopic ellipsometry data using the Tauc-Lorenz model.