The thermal expansion behaviour of a number of commercially-available and experimental continuous fibre-reinforced PEEK composites is assessed. The thermal expansion characteristics of Hercules AS4 reinforced PEEK (APC-2/AS4, ICI Fiberite) are reported in some detail, and it is shown that behaviour is both reasonable and predict able. Further, it is found that repeated thermal cycling between —160°C and + 120°C (—256°F and +248°F) has no effect on the behaviour of unidirectional laminates, and that the inherent characteristics of the composite are likely to promote such insensitivity.
In back-end of line processing (BEOL), the polymer deposited on the dielectric sidewalls during the etch process must be removed prior to subsequent processing steps to achieve high adhesion and good coverage of materials deposited in the etched features [1, . Typically, this is done by a combination of a short plasma treatment and a diluted wet clean, or by wet cleans alone. On the one hand, for porous dielectric stacks, a mild plasma treatment that preserves the integrity of the low-k dielectrics would not be sufficient to effectively remove this residue. With regard to wet clean, diluted aqueous solutions (e.g. HF-based) are not efficient for polymer removal without etching the underlying dielectric to lift off the polymer, leading to unacceptable critical dimension (CD) loss. In addition, analytical techniques available for direct characterization of sidewall residues are limited. For a fast screening of potential chemistries capable of dissolving/removing polymer residues generated during the low-k etch, a model fluoropolymer was deposited on a blanket, checkerboard low-k substrate. The present study mainly focused on the characterization of model polymer after deposition (as-deposited) and after immersion in aqueous and solvent-based cleaning solutions. The polymer removal efficiency was influenced/ improved by UV treatments prior to wet clean processes. In the second part of the study, selected UV treatment conditions and cleaning solutions were applied to low-k patterned structures using Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) to characterize the dielectric sidewall before and after UV modification and the subsequent cleaning process.
In semiconductor manufacturing, potential wetting issues are becoming a concern as feature dimensions are continuously scaled down and novel materials with different wetting properties are introduced in new technology nodes. The wetting behavior of silicon nanopillars with different dimensions and surface modifications has been studied using static contact angle (θ), attenuated total reflection infra-red spectroscopy (ATR-FTIR), and decoration by etching. The contact angle measurements showed a consistent deviation from the classic wetting models for patterned substrates with an hydrophilic surface termination (60°<θ < 80°). The ATR-FTIR and decoration studies gave evidence for partial wetting under these conditions, resulting from the formation of long-lasting nanobubbles. However the residual gas volumes estimated by ATR-FTIR were too small to explain the contact angle deviations. It is proposed that the apparent extension of the superhydrophobic regime to lower contact angles resulted from modifications caused by the manufacturing process to the wettability of the surface of nanopillars.
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