Surface and Interface Analysis

ToF-SIMS studies of nanoporous PMSSQ materials: Kinetics and reactions in the processing of low-K dielectrics for ULSI applications

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Detailed investigations of spin-on polymethylsilsesquioxane (PMSSQ)-based low-K materials were carried out by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to identify the reaction kinetics and mechanisms occurring during the manufacturing of nanoporous dielectrics for ULSI applications. Analysis of the static SIMS fingerprints led to the identification of key species related to the PMSSQ oligomers, as well to the observation of features related to the initial functionality of the precursor materials. The intensity variations of the key species with thermal curing reveal the polymerization kinetics of the dielectric precursors. In addition, thermal decomposition and volatilization of the polymethylmethacrylate- dimethylaminoethylmethacrylate copolymer (PMMA-co-DMAEMA) porogen was established based on the detection of fragments related to the different moieties of the copolymer molecule. Porogen degradation takes place via cleavage of the DMAEMA co-monomer at low temperature, followed by volatilization of the residual PMMA-enriched polymer upon annealing at higher temperature. Several complementary phenomena occurring during the formation of these complex systems can be evaluated by ToF-SIMS, revealing major features crucial to materials development and the manufacturing of novel low-dielectric-constant (K) dielectrics. Copyright © 2004 John Wiley & Sons, Ltd.