Superconformal chemical vapor deposition using plasma-generated atomic species as a consumable growth inhibitor

We describe a convenient and broadly applicable method that affords the superconformal growth of films in trenches and other recessed features by chemical vapor deposition, here applied to the growth of the metal diborides CrB2 and HfB2. A flux of atomic hydrogen or nitrogen, generated by a remote plasma source, strongly inhibits growth near the feature opening, possibly by tying up dangling bonds. In a trench, the flux of atomic species declines rapidly with depth due to wall reactions, either by recombination to afford inactive H2 or N2 or incorporation into the film. As a result, the inhibition effect decreases with depth, and the growth is almost uninhibited toward the bottom of the feature. These circumstances produce a superconformal, “V-shaped” growth profile with the vertex toward the bottom. With continued deposition, the vertex moves up and out of the feature without pinch-off, i.e., no void or seam. The use of atomic hydrogen as the inhibitor of the CrB2 growth introduces no significant impurities and does not alter the film stoichiometry, in contrast, atomic nitrogen becomes incorporated into the HfB2 film. A model of the trench filling is developed, which uses lumped kinetic parameters to calculate the film growth rate and the Knudsen diffusion to calculate transport down the axis of the trench. Model calculations agree well with experimental film thickness profiles as a function of growth time, showing that the model can be used to determine the optimal inhibitor flux as a function of the trench aspect ratio. This method should be applicable to the superconformal growth of a wide variety of film compositions as well.