Low hydrogen content silicon nitride films from electron cyclotron resonance plasmas

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Abstract
The material and electrical properties of SiNx:H films deposited using a 2% SiH4/N2 mixture with additional N2 in an electron cyclotron resonance reactor have been evaluated. Deposition rate, refractive index, and stoichiometry have been determined using ellipsometry, Rutherford backscattering spectrometry, and infrared spectroscopy. Current‐voltage and dielectric breakdown characteristics have been measured on metal‐insulator‐silicon structures. Stoichiometric material with a hydrogen content of 1.5 at. % is created using a ratio of SiH4/N2=0.003, P=2 mTorr, T=250 °C, and power=650 W. Hydrogen levels are reduced by using lower ratios of SiH4/N2, lower total pressure, or higher microwave power. Higher total pressure results in significantly enhanced deposition rates, but with greatly increased H and O content. The low‐field resistivity of these films is largely independent of the process parameters over the range investigated. The dielectric breakdown strength is significantly greater in films deposited at higher temperature, but is somewhat degraded in films deposited at lower ratios of SiH4/N2, despite the higher density and lower hydrogen content of these films.