Superconformal growth and trench filling using a consumable inhibitor in chemical vapor deposition of Hf1−xVxBy

Abstract

Three-dimensional nanodevice architectures require the coating and filling of deep vias and trenches, leading to an ongoing demand for dry processes with step coverages equal to or greater than one. We describe a new superconformal chemical vapor deposition process based on the use of two precursors: The first precursor readily deposits to afford film growth, but it cannot fill trenches when used alone because the coating is subconformal. The second precursor inhibits the deposition rate of the first precursor, and it grows film relatively slowly so that the overall film growth rate decreases when both precursors are present. In a trench, the inhibitor significantly suppresses the growth rate at the trench opening, but its pressure declines with depth due to consumption (film growth on the sidewalls) and the suppression effect weakens. Near the opening of the trench, where the inhibitor pressure is high, the consumption rate of the first precursor is small; it, therefore, diffuses deep into the trench to afford a growth rate that increases toward the bottom. If the flux of the inhibitor is not too high and the uninhibited growth rate of the first precursor is larger than that of the inhibitor, then the resulting film will be superconformal. We demonstrate this superconformal process for the growth of a metallic ceramic alloy, Hf1−xVxBy, in which the vanadium-bearing precursor serves as the consumable inhibitor. A continuous, single-step process is used to fill trenches with aspect ratios up to 10 with no void or seam along the centerline. We develop a model that captures the trench filling kinetics using Langmuirian growth kinetics, in which the two precursors compete for available adsorption sites and have different reaction rates. Calculations using physically plausible model parameters agree well with measured results and can be used to predict filling as a function of the aspect ratio. The model also indicates why filling fails at very high aspect ratios. In principle, a superconformal film of constant composition could be obtained using two precursors that each afford the same material.