Alessandro Veneroni

New Achievements on CVD Based Methods for SiC Epitaxial Growth

The results of a new epitaxial process using an industrial 6x2” wafer reactor with the introduction of HCl during the growth have been reported. A complete reduction of silicon nucleation in the gas phase has been observed even for high silicon dilution parameters (Si/H2>0.05) and an increase of the growth rate until about 20 µm/h has been measured. No difference has been observed in terms of defects, doping uniformity (average maximum variation 8%) and thickness uniformity (average maximum variation 1.2 %) with respect to the standard process without HCl.

Film Morphology and Process Conditions in Epitaxial Silicon Carbide Growth via Chlorides Route

A simplified deposition model, involving both the description of the deposition and of the film morphology was adopted to quantitatively understand the experimental trends encountered in the epitaxial silicon carbide deposition in an industrial hot wall reactor. The attention was focused on the system involving chlorinated species because its really superior performances with respect the traditional silane/hydrocarbons process. The evolution of the crystalline structure (i.e., from poly to single) and of the surface roughness can be understood by simply comparing two characteristic times, like those inherent the surface diffusion and the matter supply to the surface.

Epitaxial Deposition of Silicon Carbide Films in a Horizontal Hot-Wall CVD Reactor

The present production processes for epitaxial SiC do not allow the matching of productivity with the material quality requested by the microelectronics market. Here, to respond to such a demand, a combined experimental and multi-scale – multi-hierarchy modeling approach was adopted. Models allow to verify a priori the role of process operative parameters on the performance ones for both the final product and of the process itself, like growth rate uniformity, film stoichiometry and dopants incorporation, homogeneous nucleation of particulate, microdefects and film morphology. Specifically, in this work the developing of a lumped deposition mechanism is addressed

A Multiscale Study of the Epitaxial CVD of Si from Chlorosilanes

The deposition of epitaxial thin solid films of Si from chlorosilanes was investigated using a multiscale approach. Gas phase and surface kinetic schemes were developed using kinetic constants that, when not found in the literature, were calculated using density functional and transition state theory. Temperature fields, velocity profiles and mass transport rates inside the deposition reactor were calculated solving mass, momentum and energy conservation equations in two dimensions. Finally, the morphology evolution of the film was investigated with three-dimensional Kinetic Monte Carlo. Diffusion parameters of adsorbed Cl atoms were calculated with density functional theory representing the surface as clusters. The results of the simulations show that the surface chemistry might be more complicated than expected. The calculated presence of a significant concentration of islands and rough terrace steps is in fact likely to influence the HCl desorption kinetics, which appears now to be not consistent with experimental data.

A multiscale approach to the study of epitaxial film evolution during MOCVD

The Metal Organic Chemical Vapor Deposition (MOCVD) of GaAs, GaN, ZnSe, CdTe and AlAs is widely used for the manufacturing of electronic and optoelectronic devices. The growth is usually determined by the interaction of gas phase precursors with a heated substrate. The quality of the grown film, which depends greatly from the operating conditions of the deposition reactor, is a key parameter in the optimization of the MOCVD process. For this reason it is extremely important to have a good comprehension of the chemical and physical phenomena that take place during the film growth and in particular of the gas phase and surface chemistry of the deposition process [1].