Temperature dependence of the etch rate and selectivity of silicon nitride over silicon dioxide in remote plasma NF3/Cl2

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The etch rates and selectivity of Si3N4 over SiO2 have been investigated by microwave discharging a mixture of NF3 and Cl2 and flowing the resultant fluorine and chlorine atoms and interhalogenous molecules simultaneously over a silicon wafer covered with low pressure chemical vapor deposition (LPCVD) Si3N4, and a wafer covered with thermally grown SiO2. The temperature dependence of the etch rates of Si3N4 and SiO2 in the NF3/Cl2 mixture was examined in the range from 25 to 500 °C, and the selectivity of the nitride etch over the oxide etch as well as nitride etch rate was found to increase with increasing temperature. It was also found that both etch rates and selectivities increase with NF3 flow rates within the range used in this study.