Etching of chemically vapour-deposited amorphous Si₃N₄-C composites in HF solution

Amorphous Si₃N₄-C[Am.CVD-(Si₃N₄] composites (C: 0.6 to 6 wt%) were prepared by chemical vapour deposition (CVD) using SiCl₄, H₂, NH₃and C₃H₈ gases, and their etching characteristics in 47% hydrofluoric acid (HF) solution were investigated in the temperature range of 25 to 50° C. It was found that the etching rate decreases with increasing carbon content. The etching rate of the Am.CVD-(Si₃N₄-C) composite containing 6 wt% carbon was about 1/40 of the rate for carbon free Am.CVD-Si₃N₄. The activation energies obtained from the temperature dependence of the etching rates were 11 to 17 kcal mol^-1, which increased with increasing carbon content. This paper also presents the study on the characteristics of the etched surfaces as well as the carbon state in the Am.CVD-(Si₃N₄-C) composites, and finally the possible etching mechanism is discussed.