*S.G. Walton¹, D.R. Boris¹, V.D. Wheeler¹, N. Nepal¹, S.G. Rosenberg², J. Avila² J.M. Woodward², V.R. Anderson², C.R. Eddy, Jr.^1
1U.S. Naval Research Laboratory, Washington, DC; ²Postdoctoral Fellow, ASEE, Washington, DC
Plasma assisted atomic layer deposition (PA-ALD) is a low temperature, conformal, layer-by-layer deposition technique that is based on a pair of self-terminating and self-limiting gas-surface half-reactions, in which at least one half-reaction involves species from a plasma. This approach generally offers the benefit of substantially reduced growth temperatures and greater flexibility in tailoring the gas-phase chemistry to produce films of varying characteristics. The advantages come at the cost of a complex array of process variables that often require great care on the part of the user. We employ plasma diagnostics to inform the choice of process conditions for PA-ALD systems including VUV-NIR spectroscopy, charged particle collectors near the substrate, and spatially resolved Langmuir probe measurements to characterize the plasma used in a commercial PA-ALD tool (Fiji 200; Ultratech/CNT). In particular, we assess the total ion flux reaching the substrate surface, spatial variation of plasma properties, and the relative fractions of atomic and molecular species generated in the plasma under a variety of pressures and gas input flow fractions typically employed to grow nitride and oxide films. Changes in plasma parameters are then linked with changes in the characteristics of films including AlN₂ InN, TiO₂ and Ga₂O₃.