Dependence of wet etch rate on deposition, annealing conditions and etchants for PECVD silicon nitride film

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition (PECVD) silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiN_x:H by HF solution. A low etch rate was achieved by increasing the SiH₄ gas flow rate or annealing temperature, or decreasing the NH₃ and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for SiO₂ and SiN_x:H. A high etching selectivity of SiO₂ over SiN_x:H was obtained using highly concentrated buffered HF.