Silicon nitride and silicon etching by CH3F/O2 and CH3F/CO2 plasma beams

Silicon nitride (SiN, where Si: N 6 not equal 1:1) films low pressure-chemical vapor deposited on Si substrates, Si films on Ge on Si substrates, and p-Si samples were exposed to plasma beams emanating from CH3F/O-2 or CH3F/CO2 inductively coupled plasmas. Conditions within the plasma beam source were maintained at power of 300W (1.9W/cm(3)), pressure of 10 mTorr, and total gas flow rate of 10 sccm. X-ray photoelectron spectroscopy was used to determine the thicknesses of Si/Ge in addition to hydrofluorocarbon polymer films formed at low % O-2 or % CO2 addition on p-Si and SiN. Polymer film thickness decreased sharply as a function of increasing % O-2 or % CO2 addition and dropped to monolayer thickness above the transition point (similar to 48% O-2 or similar to 75% CO2) at which the polymer etchants (O and F) number densities in the plasma increased abruptly. The C(1s) spectra for the polymer films deposited on p-Si substrates appeared similar to those on SiN. Spectroscopic ellipsometry was used to measure the thickness of SiN films etched using the CH3F/O-2 and CH3F/CO2 plasma beams. SiN etching rates peaked near 50% O-2 addition and 73% CO2 addition. Faster etching rates were measured in CH3F/CO2 than CH3F/O-2 plasmas above 70% O-2 or CO2 addition. The etching of Si stopped after a loss of similar to 3 nm, regardless of beam exposure time and % O-2 or % CO2 addition, apparently due to plasma assisted oxidation of Si. An additional GeOxFy peak was observed at 32.5 eV in the Ge(3d) region, suggesting deep penetration of F into Si, under the conditions investigated. (C) 2016 American Vacuum Society.