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Silicon nitride (SiN, where Si:N ≠ 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/O2 or CH3F/CO2 inductively coupled plasmas. Conditions within the plasma beam source were maintained at power of 300W (1.9W/cm³), 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%O2 or %CO2 addition on p-Si and SiN. Polymer film thickness decreased sharply as a function of increasing %O2 or %CO2 addition and dropped to monolayer thickness above the transition point (~48% O2 or ~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/ O2 and CH3F/CO2 plasma beams. SiN etching rates peaked near 50% O2 addition and 73% CO2 addition. Faster etching rates were measured in CH3F/CO2 than CH3F/O2 plasmas above 70% O2 or CO2 addition. The etching of Si stopped after a loss of ~3 nm, regardless of beam exposure time and %O2 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. [ABSTRACT FROM AUTHOR]

A CH3F/CO2 inductively coupled plasma (ICP), sustained in a compact plasma reactor, was investigated as a function of power (5-400 W) and feed gas composition, at a pressure of 10 mTorr, using optical emission spectroscopy and rare gas actinometry. Number densities of H, F, and O increased rapidly between 74% and 80% CO2, ascribed to the transition from polymer-covered to polymer-free reactor walls, similar to that found previously in CH3F/O2 ICPs at 48% O2. Below 40% O2 or CO2, relative emission intensity ratios were almost identical for most key species in CH3F/O2 and CH3F/CO2 ICPs except for higher OH/Xe (a qualitative measure of OH and H2O densities) over the full range of CH3F/O2 composition. The number density of H, F, and O increased with power in CH3F/CO2 (20%/80%) plasmas (polymer-free walls), reaching 4.0, 0.34, and 1.6 × 1013/cm³, respectively, at 300 W. The CO number density increased with power and was estimated, based on self-actinometry, to be 8.8 × 1013/cm³ at 300 W. The CO2 number density was independent of power below 40 W (where very little decomposition occurred), and then decreased rapidly with increasing power, reaching 2.8 × 1013/cm³ at 300 W, corresponding to 83% dissociation. Films deposited on p-Si, 10 cm from the open, downstream end of the plasma reactor, were analyzed by x-ray photoelectron spectroscopy. Between 10% and 40% CO2 or O2 addition to CH3F, film deposition rates fell and O content in the films increased. Faster deposition rates in CH3F/CO2 plasmas were ascribed mainly to a larger thermodynamic driving force to form solid carbon, compared with CH3F/O2 plasmas. Oxygen content in the films increased with increasing CO2 or O2 addition, but for the same deposition rate, no substantial differences were observed in the composition of the films. [ABSTRACT FROM AUTHOR]

Atomic layer etching (ALE) of SiO2 was studied by alternating exposure of a 5 nm-thick SiO2 film on Si substrate to (1) a plasma beam emanating from a c-C4F8 inductively coupled plasma (ICP), to grow a fluorocarbon (FC) film composed mainly of CF2, and (2) an energetic (130 eV) Ar+ ion beam extracted from a separate Ar ICP. In situ x-ray photoelectron spectroscopy was used to analyze the chemical composition of the near-surface region, and to quantify the thickness of the FC and SiO2 films. A very thin (3–6 Å), near self-limiting thickness CF2-rich FC film was found to deposit on the SiO2 surface with exposure to continuous or pulsed power C4F8 plasma beams, under conditions that generated a large relative flux of CF2. Following this, a FC film of similar composition grew at ~10 times slower rate. Exposure of the thin film to the Ar+ beam led to removal of 1.9 Å SiO2. An estimated yield of 1.3 SiO2 molecules-per-Ar+ was found for a single ALE step. The rate of 1.9 Å/cycle persisted over multiple ALE cycles, but a carbon-rich residual film did build up. This film can be removed by a brief exposure to an O2-containing plasma beam. [ABSTRACT FROM AUTHOR]