High density plasma oxide etching using nitrogen trifluoride and acetylene

Abstract

The use of nitrogen trifluoride (NF3) and acetylene (C2H2) in the presence of helium has been examined for oxide etching in an inductively coupled, high density plasma etch tool. Oxide etch rates have been measured for blanket films and for patterned wafers with features of 0.6, 0.45, and 0.35 μm nominal critical dimension, while process performance has been assessed with cross-sectional scanning electron microscopy. Optical emission spectroscopy has been employed in situ to characterize the species present in the plasma, and quadrupole mass spectrometry has been used to analyze process effluent sampled between the chamber outlet and the turbo pump inlet. Polymer film deposited on the surface of the oxide layer has been studied with time-of-flight secondary ion mass spectrometry. Global warming emissions for a range of process conditions have been quantified using Fourier transform infrared spectroscopy, and are compared to emissions from more typical oxide etch processes on the same tool type. Results indicate that the NF3/C2H2 chemistry is capable of etching oxide anisotropically, while offering a significantly lower global warming impact than current oxide etch chemistries.