Seamless fill of deep trenches by chemical vapor deposition: Use of a molecular growth inhibitor to eliminate pinch-off

Attempts to fill deep trenches by chemical vapor deposition often result in a “bread-loaf” profile, an overhang near the trench opening that arises whenever the growth rate is slightly higher near the opening than deeper in the feature. Continued growth leads to premature pinch-off at the opening, which leaves an undesirable void or seam along the centerline. Bread-loaf profiles can form even under superconformal growth conditions, as the authors recently found for the growth of HfO2 from the precursor tetrakis(dimethylamino)hafnium and a forward-directed flux of H2O coreactant. The current paper describes a method that can reduce or eliminate the bread-loaf problem: addition of an isotropic flow of a reactant that inhibits growth near the trench opening but leaves the growth rate unchanged deeper in the trench. A Markov chain model for ballistic transport of the inhibitor inside trenches is developed to account for this behavior: the model reveals that suppression of a bread-loaf profile is best accompli...