Growth Inhibitor To Homogenize Nucleation and Obtain Smooth HfB2 Thin Films by Chemical Vapor Deposition

Abstract

We describe an example of a new phenomenon: the use of a growth inhibitor to homogenize nucleation and improve the smoothness of a thin film deposited by chemical vapor deposition. For many film–substrate combinations, the rate of nucleation on the substrate is slow relative to the growth rate, a situation that produces a broad distribution of island sizes and a rough surface morphology. We show an example in which this outcome is avoided by directing a second component onto the substrate that has little effect on the nucleation rate but significantly retards the island growth rate. The case studied is the growth of HfB2 films on SiO2 substrates using the chemical vapor deposition precursor Hf(BH4)4 with NH3 as the inhibitor. The addition of the inhibitor increases the island density at coalescence by 50× and decreases the roughness by 10× to the subnm range. We suggest that the use of inhibitors to homogenize nucleation may be applicable to other film–substrate combinations.