Molecular Dynamics Analysis of Physical and Chemical Behavior of Etch Products Desorbed during Si Etching in Cl- and Br-based Plasmas

Profile anomalies and surface roughness are critical issues to be resolved in plasma etching of nanometer-scale microelectronic devices, which in turn requires a better understanding of the effects of ion incident energy and angle on surface reaction kinetics. This paper presents a classical molecular dynamics (MD) simulation of Si etching by energetic Cl$^{+}$ and Br$^{+}$ ion beams with different incident energies ($E_{i}$ = 20--300 eV) and angles (\textit{$\theta $}$_{i}$ = 0--85$^{\circ}$), and low-energy neutral Cl and Br radicals with different neutral radical-to-ion flux ratios ($\Gamma _{n}$/$\Gamma _{i}$ = 0--100), where the improved Stillinger-Weber interatomic potential is used for Si/Cl and Si/Br systems. Emphasis is placed not only on the etch yield and stoichiometry, but also on the energy and angular distributions of etch products desorbed. Numerical results indicated that as $\Gamma _{n}$/$\Gamma _{i}$ is increased at high $E_{i} >$ 100 eV, the Si etch yield and the amount of products containing more halogen atoms increase, where the energy distribution of desorbed etch products peaks at lower energies. In addition, the desorption angle of etch products, which is measured from the surface normal on substrates, become slightly smaller with increasing $\Gamma _{n}$/$\Gamma _{i}$, which is more clearly observed in the case of oblique ion incidence.