Surface Reactivity and Plasma Energetics of SiH Radicals during Plasma Deposition of Silicon-Based Materials

The surface reactivity of the SiH radical was measured during plasma deposition of various silicon-based materials using the imaging of radicals interacting with surfaces (IRIS) method. In this technique, spatially resolved laser-induced fluorescence (LIF) is used to determine surface reaction probabilities, R or β, of plasma species. For SiH, R is near unity, 0.96 ± 0.04, and shows no dependence on the gas mixture (SiH4, Si2H6, SiH4/H2, Si2H6/H2, SiH4/NH3, SiH4/N2, and SiH4/CH4) or on the plasma conditions used. The velocity of SiH in the molecular beam has also been measured, yielding the SiH kinetic translational temperature in the plasma. Modeling of the kinetic data yields an average SiH translational temperature of ∼1100−1200 K for both SiH4 and Si2H6 plasmas, which is nearly independent of the applied rf plasma power. The rotational temperature determined from the SiH rotational spectrum is ∼600 K for both plasmas, also with no clear dependence on applied power. The difference in these temperatures is explained by examining energy dissipation in the inductively coupled plasma, suggesting that the translational temperature of SiH is determined by the excess energy released during the dissociation of SiH4 or Si2H6 by electron impact.