Paper PS2-TuA4
Enhanced SiN Etching by Hydrogen Radicals during Fluorocarbon/Hydrogen Plasma Etching; Molecular Dynamics Simulation Analyses

Tuesday, October 20, 2015, 3:20 pm, Room 210B

Selective etching of silicon nitride (SiN) over silicon dioxide (SiO₂) or vice versa has been widely used in microelectronics fabrication processes. Plasmas derived from fluorocarbon (FC) gas with hydrogen (H₂) and/or hydrofluorocarbon (HFC) gas are typically used for etching processes of SiN. Our recent study using molecular dynamics (MD) simulations on surface reactions of SiN and SiO₂ with incident CHF₂⁺ and CF₂⁺ ions supplied by a HFC or FC/H₂ plasma has found that hydrogen supplied from incident ions inhibits the formation of FC polymer on the SiN surface during the process, which facilitates the formation of volatile SiF_x species on the SiN surface and therefore enhances its sputtering yield [1]. In the present study, we have also examined whether hydrogen reacts with a SiN or SiO₂ surface directly, by supplying more hydrogen to SiN and SiO₂ surfaces in MD simulations. An earlier experimental study [2] has showed that the SiN sputtering yield increases as the supply of hydrogen to the CF plasma increases. Following such an experiment, in this study, we have varied the amount of hydrogen radicals supplied to the SiN and SiO₂ surfaces and examined how their sputtering yields by CF_x⁺ ions change, depending on the amount of hydrogen adsorbed on the surfaces. Detailed examinations of desorbed species and surface chemical compositions obtained from MD simulations of such processes have indicated that hydrogen in FC/H₂ plasmas react with nitrogen of the SiN surface to form volatile NH_x, most dominantly NH₃, to promote the surface etching whereas it hardly affects the sputtering yield of SiO₂ under the same conditions.

References

[1] K. Miyake, et al., Jpn. J. Appl. Phys. 53 03DD02 (2014).

[2] M. Fukasawa, et al., Jpn. J. Appl. Phys. 48 08HC01(2009).