Vibrational spectroscopy characterization of low-dielectric constant SiOC:H films prepared by PECVD technique |
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Authors: | G Das G Mariotto A Quaranta |
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Affiliation: | aINFM and Dipartimento di Fisica, Università di Trento, Via Sommarive 14, 38050 Povo (Trento), Italy;bDipartimento di Ingegneria dei Materiali e delle Tecnologie Industriali, Università di Trento, Via Mesiano 77, 38050 Povo (TN), Italy |
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Abstract: | Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition (PECVD) from trimethyl-silane (H–Si–(CH3)3) and ozone (O3) gas mixture. The samples were preliminarily annealed at 400 °C in N2 atmosphere and then in N2+He plasma. Afterwards, they were treated in vacuum at some fixed temperatures in the range between 400 and 900 °C. Structural investigations of the annealed films were carried out by means of vibrational spectroscopy techniques. FT-IR spectrum of a preliminarily treated sample shows absorption bands due to stretching modes of structural groups like Si–CH3 at 1270 cm−1, Si–O–Si at 1034 cm−1 and C–Hx in the region between 2800 and 3000 cm−1. No significant spectral change was observed in the absorption spectra of samples annealed up to 600 °C, indicating that the preliminarily treated film retains a substantial structural stability up to this temperature. Above 600 °C, absorption spectra show a strong quenching of H-related peaks while the band due to Si–O–Si anti-symmetric stretching mode shifts towards higher energy, approaching the value observed for thermally grown SiO2. Raman spectra of samples treated at temperatures T500 °C exhibit both D and G bands typical of sp2-hybridised carbon, due to the formation of C–C bonds within the film which is accompanying the release of hydrogen. The intensity of D and G bands becomes more pronounced in samples annealed at higher temperatures, thus suggesting a progressive precipitation of carbon within the oxide matrix. |
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Keywords: | Carbon-doped silicon oxide Low-dielectric constant films Vibrational spectroscopy |
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