Paper PS-FrM5
Molecular Dynamics Study on Collision Cascade Dynamics for Sputtering of Lennard-Jones Particles

Friday, October 26, 2018, 9:40 am, Room 104A

Plasma etching techniques have been widely used to manufacture semiconductor devices. The sizes of typical silicon (Si) based semiconductor devices are now reaching atomic sizes. The further development of plasma etching techniques to fabricate such small devices requires a better understanding of plasma-surface interactions between the material surface and impacting plasma species. Especially when the device sizes are in the range of nanometers, a high precision in plasma control is one of the key challenges for the manufacturers to obtain desired results and avoiding unwanted effects in manufactured devices. For example, during an etching process with energetic ions impacting on the material surface, surface damages caused by energetic ion bombardment may lead to the formation of non-functional regions in manufactured devices. For nanometer scale semiconductor devices, nanometer-scale plasma-induced defects in their electrically active regions typically impair the device performance. Since the last century, the interaction between a surface and an energetic incident particle as well as the collision cascade resulting from it has been widely studied, which has led to the establishment of several theories. However sputtering phenomena are highly non-linear and the system is not in thermal equilibrium, so none of these theories provides a comprehensive description of collision cascade dynamics, even for a simple case of two-body interactions such as the Lennard-Jones (LJ) interaction. In this study, as a model system, physical sputtering of a cool Lennard-Jones solid, i.e., a solid that consists of particles interacting with two-body LJ interactions and is in thermal equilibrium at a temperature sufficiently below its melting temperature, is examined with the use of Molecular Dynamics (MD) simulations. The goal of this study is to understand how the interatomic potential function of a material affects its sputtering yield, a macroscopic and non-thermodynamical property of the material. Self-sputtering of a LJ material and physical sputtering of a LJ material by the incidence of energetic non-reactive particles with different sizes and masses were examined. A non-reactive particle in this study is the one that interacts with other particles via a repulsive part of a LJ potential. From MD simulation, dependence of the sputtering yield on the normalized incident energy and the incidence angle has been obtained for different mass ratios and atomic-radius ratios between the substrate and impacting particles.