Supersonic Molecular Beams

for Thin Film Deposition

Thin films and the processes employed to fabricate them play an increasingly important role in a variety of technologies. The use of supersonic molecular beams as sources represents a novel approach to thin film growth. It has been demonstrated that the surface reaction probability can be greatly enhanced by increasing reactant kinetic energy, which can be readily achieved by using supersonic molecular beams. The goal of this study is to obtain better understanding of collimated molecular beams and to provide accurate predictions of experiments being conducted in the School of Chemical Engineering at Cornell University. The ultimate goal of our work is to help to optimize the deposition process.

The current study considers expansion of a mixture of 1% disilane (Si2H6) and 99% H2 from a nozzle orifice, through a conical skimmer, and into the growth chamber. Silicon film is deposited over the substrate surface. The direct simulation Monte Carlo method (DSMC) is employed to simulate this flow. An adaptive unstructured triangular grid is used to capture the density drop in the expansion flow. Models are under development for more accurate simulation.


This work was funded by the National Science Foundation.