Etching characteristics of PECVD-prepared SiN films with CF4/D2 and CF4/H2 plasmas at different temperatures

The dependences of plasmas (CF
₄
/D
₂
and CF
₄
/H
₂
) on etch rates of the PECVD SiN films at different substrate temperatures were investigated. The CF
₄
/D
₂
plasma exhibited higher etch rates than that for the CF
₄
/D
₂
plasma at room temperature and higher. The optical emission spectra showed that the CF polymerization, F and Balmer emissions were stronger in the CF
₄
/D
₂
plasma, by comparing with the CF
₄
/H
₂
plasma. A thinner fluorocarbon thickness with a lower F/C ratio was found in the sample proceeded by the CF
₄
/H
₂
plasma. The fluorocarbon thickness and gas phase concentration were not responsible for the increase of etch rate in the CF
₄
/D
₂
plasma. The abstraction of H inside the SiN films by deuterium and hydrogen dissociation were considered to be important for the etching of the Si- H bond rich SiN films.