Surface segregation of photoresist copolymers containing polyhedral oligomeric silsesquioxanes studied by x-ray photoelectron spectroscopya)
Schematic representation of the various monomers. C and O atom labeling refer to the different chemical environments used for XPS peak fitting.
Example of high resolution (a) and (b) XPS spectra for the 30% material. Peak labeling refers to the indexation in Fig. 1.
ARXPS results. Evolution of silicon content (a), carbonyl groups (C5) (b), C–Si bonds (C1) (c), and O–Si bonds (O5) (d) vs normalized probed depth. In graph (a) horizontal lines indicate the theoretical Si percentage for each material. Variation of and ratios are also represented respectively in graphs (c) and (d).
Silicon (a) and carbon (b) XPS wide scan for 100%, 60%, 40%, and 20% ethyl-POSS copolymers. In order to compare backgrounds, all spectra are normalized to or contribution.
Depth profile results obtained with the QUASES™ software. Comparison between experimental and generated spectrum with the island model for the 20% ethyl-POSS copolymer (a) shows a large difference at low kinetic energy. Best results for 20% (b), 40% (c), and 60% ethyl-POSS (d) materials are obtained with an exponential profile.
Silicon atomic percentage measured by ARXPS compared to silicon atomic percentage calculated using the results of the inelastic background analysis.
XPS silicon spectra for 30% and 30% copolymers, compared to that of 40% and 60% ethyl-POSS copolymer.
Bond and atomic theoretical percentages for the different copolymers. Binding energy corresponding to the various chemical environments is also indicated. (Copolymers are labeled according to their weight percentage in ethyl-POSS). XPS atomic quantification is reported and for Si the relative difference with theory is shown.
Comparison of silicon content obtained by theoretical calculations, ARXPS, and background analysis for the various copolymers.
Copolymer base unit characteristics. The last line corresponds to the calculated value of bulk silicon concentration relatively to PMSQ .
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