Reactive Magnetron Sputtering of Silicon in AR + CH4: Identity and Energy of the Slc Growth Species

Double-modulation mass spectrometry is used to analyze the identity and energy distribution of the particle flux during low-temperature growth of Si1−xCx by reactive magnetron sputtering of a silicon target in 3 mTorr argon and 0 – 0.35 mTorr methane. The ion fluxes, methane consumption, film deposition rate, and film composition are determined as a function of the methane partial pressure at fixed target current. Argon, silicon, carbon and hydrocarbon ions are detected at the substrate position. The argon and hydrocarbon ions have a narrow energy distribution consistent with the plasma potential. The silicon and carbon ions have a broad energy spread, consistent with that of sputtered neutrals which are post-ionized by the plasma. The film composition (C/Si) varies in the same manner as the arrival ratio of (C+/Si+) ions, but does not correlate well with the arrival ratio of (ΣCHX+/Si+) ions or the methane consumption rate. We conclude that the main source of carbon in Si1−xCx films is the sputtering of C atoms from the Si target surface.