AVS 65th International Symposium & Exhibition
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM6
Surface Reaction Analysis by Molecular Dynamics (MD) Simulation for SiO2 Atomic Layer Etching (ALE)

Friday, October 26, 2018, 10:00 am, Room 104A

Session: Plasma Modeling
Presenter: Satoshi Hamaguchi, Osaka University, Japan
Authors: S. Hamaguchi, Osaka University, Japan
Y. Okada, Osaka University, Japan
M. Isobe, Osaka University, Japan
T. Ito, Osaka University, Japan
K. Karahashi, Osaka University, Japan
Correspondent: Click to Email
Alternating application of fluorocarbon plasmas with no bias energy and Ar plasma with low bias energy to a SiO2 film is known to cause atomic layer etching (ALE) of its surface. In this ALE process, it is assumed that a thin layer of fluorocarbon is deposited on the SiO2 surface in the first step and low-energy Ar+ ion irradiation causes mixing of deposited fluorocarbon with atoms of the underlying SiO2 surface in the second step, promoting desorption of volatile SiFx and CO from the surface until fluorocarbon on the surface is completely exhausted. In this study, we have examined the surface reactions of such processes, using molecular dynamics (MD) simulations. It has been found, however, the actual surface reactions are not as simple as described above. In the Ar+ ion irradiation step, preferential sputtering of O atoms occurs even at low ion incident energy, which makes the surface more Si rich and also promotes the formation of Si-C bonds in the presence of a deposited fluorocarbon layer. In other words, in deficiency of O atoms on a SiO2 film surface, low-energy Ar+ ion irradiation may not be able to remove C atoms completely from the surface. Under such conditions, more carbon atoms may remain on the surface after each ALE cycle and etch stop may eventually occur after several ALE cycles. On the other hand, our simulation results indicate that a small amount of oxygen added to Ar+ ion irradiation may contribute to more efficient removal of carbon from the surface and also supplement the deficiency of oxygen caused by the preferential sputtering of oxygen from the surface. Simulation results are also compared with experimental observations of SiO2 ALE based on fluorocarbon plasmas.