A method for high selective etch of Si3N4 and SiC with ion modification and chemical removal

We demonstrated a high selective and anisotropic plasma etch of silicon nitride (Si3N4) and silicon carbide (SiC). The demonstrated process consists of a sequence of ion modification and chemical dry removal steps. The Si3N4 etch with hydrogen (H) ion modification showed a high selectivity to silicon dioxide (SiO2) and SiC films without hydro fluorocarbon film deposition which has been used in a conventional Si3N4 etch process. A self-limiting reaction was observed by changing the ion modification and removal step times. The SIMS analyzes indicated that the etch amount of Si3N4 depends on not only penetration depth of H ion but also H concentration in the ion modification step. In addition, we have developed selective etch of SiC with nitrogen (N) ion modification. These results suggest that the ion modification assisted etch enables us to obtain the high selective Si3N4 or SiC film by H or N ion modification, respectively.