Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF 4 /H 2 plasma at different substrate temperatures

Abstract The dependences of etching characteristics on substrate temperature ( T s , 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 CF 4 /H 2 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 T s , due to the different FC thickness and etching mechanisms proposed. The formation of the N−H x layer on PE‐SiN at low temperature caused the decrease in ER. For the LP‐SiN, the weak dependences of T s on surface structure and ER were observed.