Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF4/H2 plasma at different substrate temperatures

The dependences of etching characteristics on substrate temperature (Ts, from –20 to 50°C) of the plasma‐enhanced chemical vapor deposition (PECVD) SiN films (PE‐SiN) and low‐pressure chemical vapor deposition (LPCVD) SiN films (LP‐SiN) with CF4/H2 plasma were investigated. The Fourier‐transform infrared spectroscopy shows that both film types were N–H bond‐rich films, but in different hydrogen contents (PE‐SiN 22.7 at% and LP‐SiN 3.8 at%) from the Rutherford backscattering spectroscopy analyses. A higher hydrogen content led to a thinner fluorocarbon thickness because of the reaction between hydrogen outflux and C and N to form an HCN byproduct. The etch rates (ER) for the PE‐SiN were higher than that of the LP‐SiN at all Ts, due to the different FC thickness and etching mechanisms proposed. The formation of the N−Hx layer on PE‐SiN at low temperature caused the decrease in ER. For the LP‐SiN, the weak dependences of Ts on surface structure and ER were observed. The dependences of etching characteristics on substrate temperature of –20 to 50°C of the PECVD and LPCVD films with CF4/H2 plasma were investigated. A higher hydrogen content inside the films led to a thinner fluorocarbon thickness because of the reaction between hydrogen outflux and C and N to form an HCN byproduct. The etch rates for the PECVD film were higher than that of LPCVD at all temperatures due to the different FC thickness and etching mechanism proposed.