Surface oxide formation inhibiting the etch of a tantalum nitride (TaN) film was controlled through step pressure modulation and H2 addition in a Cl2/Ar based plasma-assisted cyclic etch process. Sources contributing to the oxidation of the film included the mask materials, specifically the silicon-containing antireflective coating, as measured by optical emission spectroscopy. Surface analysis of etched films by secondary ion mass spectroscopy showed the presence of a modified surface layer ∼2 nm thick with localized oxygen concentrations 0.02 and 0.003 that of the control sample (without and with H2 addition, respectively). Reduced Ta–O bonding observed via x-ray photoelectron spectroscopy as a result of H2 addition was found to enhance etch rate uniformity of both blanket and patterned films. Minimization of redeposited oxidized TaN on the mask sidewalls of patterned samples was achieved using this etch process and by controlling the lithographic stack composition.
Pitch subdivision of tantalum nitride (TaN) lines is demonstrated across a 200 mm wafer using a cyclic quasi‐atomic layer etch process in an inductively coupled plasma reactor. Chlorine (Cl2) and hydrogen (H
2) chemistries are introduced sequentially to an argon plasma in discrete steps to etch the TaN film. The starting lithographic pattern with critical dimension (CD) of approximately 82 nm and pitch of 200 nm thus yields lines of approximately 40 nm CD and 100 nm pitch with minimal line edge roughness increase. We identify a synergistic effect between H
2‐exposed TaN and Cl
2 plasma as contributing to this result, as well as a potential link to surface oxidation. Optical emission spectroscopy analysis of the plasma discharge is used to characterize reactive species densities and explain the observed changes in profile.
Front Cover: The ability to control individual step parameters in cyclic plasma etch processes provides novel capabilities for nanofabrication. In this example, the pitch of a line/space array is halved as the pattern is transferred into a tantalum nitride (TaN) film. The redeposition of a partially oxidized surface layer creates a self‐aligned mask, and line edge roughness (LER) is maintained by the highly selective nature of the etch.
Further details can be found in the article by Nathan Marchack, Keith Hernandez, Benjamin Walusiak, Jon‐l Innocent‐Dolor, Sebastian Engelmann (https://doi.org/10.1002/ppap.201900008).
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