Chemical dry etching of silicon nitride in F 2/Ar remote plasmas

Abstract

In this work, chemical dry etching process of the silicon nitride layers using the F 2/Ar remote plasmas generated by a toroidal-type remote plasma source was investigated by varying the total (F 2 + Ar) gas flow, the F 2/(F 2 + Ar) flow ratio, the etching temperature and the working pressure. Under the current experimental condition, the chemical etching rates of the silicon nitride were significantly enhanced with increasing the F 2 gas flow rate and F 2/(F 2 + Ar) flow ratio. Observed tendency in the etch rate was consistent with the variations of the optical emission intensity of the F radicals in the afterglow region of the remote plasma source and of the concentration of the emitted SiF 4 reaction by-product molecules. The substrate temperature was the most influential process parameter in determining the etching rates. The etching rates of the silicon nitride layers were increased by a factor of ≅ 50, 109, and 114 for the F 2 gas flow ratios of 29, 50, and 68%, respectively, as the substrate temperature increases from 25 to 350 °C.