Deposition of epitaxial silicon thin films through the seeding of silicon hydride molecules in a supersonic beam of light carrier gas is modeled using the direct simulation Monte Carlo technique. In this process, a hyperthermal collimated beam is formed by rapid expansion through a nozzle orifice and then refined through a skimmer. The fundamental characteristics of the process are evaluated quantitatively through a gas dynamics approach. General features of the internal supersonic flows are described. Detailed information is provided by the simulations on the beam properties, such as beam intensity, incident kinetic energy and angle as the precursor molecules impact the substrate surface. The thin film growth rates are quantified and film uniformity is discussed. Good agreement is achieved on the comparisons with measurements of the film growth rate and the quadrupole mass spectrometric measurements of the beam intensity. A wide range of geometric and physical parameter space is examined numerically. The effects of the skimmer interference, supersonic source temperature and size, and pumping conditions are also addressed with emphasis on the film deposition rate and uniformity.