Atomistic simulation of silicon bombardment by energetic CF₃⁺: Product distributions and energies

We present an analysis of results obtained from molecular dynamics simulations of continuous bombardment of the Si surface with CF₃⁺ ions at normal incidence in the energy (E_i) range of 25-200 eV. Our analysis is aimed at understanding how the distributions in products and their kinetic energies depend on E_i. As E_i increases, the product distribution is shifted toward a lower average molecular weight, and with atomic F and molecular CF becoming the most common product species at the higher incident energies. These findings agree well with recent experimental results. The kinetic energy distributions of the products are sensitive to E_i only in that the high-energy tail of the distribution becomes more prevalent with increasing E_i. Linear cascade theory predictions agree reasonably well with our kinetic energy distributions. Individual species product kinetic energy distributions are much more sensitive to E_i, and primarily reflect that most high-energy products are of low molecular weight. The product kinetic energy as a function of ejection angle is also sensitive to E_i, displaying an increasing maximum value with increasing E_i. These results could potentially help in the guidance and interpretation of molecular beam experiments which seek to detect products in simulated fluorocarbon plasma etching of silicon.