Crying Wulff on vapor–solid distributions of crystallogen chemical vapor deposition via p-block element hydride thermal decomposition

Abstract

Chemical vapor deposition is key in silicon device manufacturing. Surprisingly, crystallogen thin film deposition is executed without adequate knowledge of vapor–solid distributions. To address the issue, classical thermodynamics is applied to the determination of vapor–solid distributions for Si1-xCx, Si1-xGex and Ge1-xSnx depositions via a hydride route. The enthalpy of formation is substituted with a X – H bond dissociation energy which stands for the surface energy. Theory and experiments are in reasonable agreements. Indeed, the surface energy drives the solid growth, in line with Wulff’s principle. And the thermal decomposition of a covalent hydride is a quasistatic process. Chemical vapor deposition and thermal decomposition are unified with thermodynamics. Growth Rate, partial reaction order n = 1/2 and activation energy E fingerprint an interface chemistry consistently across covalent precursors. E is often found equal to a fraction of either X – H or H – H bond dissociation energy, i. e., E = n BDE, where n is a partial reaction order, and 1/n an integer matching the molecular hydrogen stoichiometric coefficient. Thus, p-Block elemental deposition mechanism is elucidated. Three sequential deposition mechanisms are identified. In the first mechanism, the growth rate is controlled by the dissociation of a X – H bond. In the second mechanism, a H – H bond dissociation is controlling the growth rate. The H – H path is triggered by a near complete surface hydrogenation. Finally, in the third mechanism, the deposition turns out amorphous from the lack of vacant lattice sites, as the H – H breaking energy is exhausted, and once more complete surface hydrogenation is achieved.