Low-energy ion beam erosion of Si with simultaneous co-deposition of metallic surfactants: Experimental and simulated data

Ion beam erosion of Si under co-deposition circumstances supports the formation of surface patterns on the nano- and micrometer scale. To evaluate the effect of surfactant sputtering within a setup relevant for ultra precision surface finishing, this work is presented. We present data for samples prepared with Ar ion beam erosion, at low ion energy. Al, Cu, steel, Cr, Ni, Mo, Ti, Ta, Zn and Si were chosen as co-deposition material. Simultaneous irradiation of the co-deposition material and the Si samples were performed with a broad beam ion source. The structuring and pattern formation are discussed with SEM and AFM measurements. It was shown that the evolution of structures on the substrate is induced by the silicide-forming metals. This corresponds with a higher surface roughness. Whereas the non-silicide-forming metals did not show patterning, and accordingly, lower surface roughness. Measurements regarding the Si removal rate showed, that it depends on the co-deposition material. Supporting simulation data proposed that the effect of the co-deposition material on the Si removal is determined by the combination of sputtering and scattering properties of the co-deposition material. The ratio of scattered Ar ions to sputtered metal particles describes the effect on the removal change. For metals which tend to higher scattering, the removal is enhanced. This applies for most of the metals with higher atomic number. Whereas the metals with lower atomic number favor self-sputtering, which results in an decreased Si removal.

Automated summary

Ion beam erosion of Si under co-deposition circumstances can form surface patterns on the nano- and micrometer scale. This study investigates the effect of surfactant sputtering on ultra precision surface finishing. It is found that the formation and evolution of structures on the substrate are induced by the silicide-forming metals, leading to higher surface roughness. On the other hand, non-silicide-forming metals do not show patterning and result in lower surface roughness. Additionally, the co-deposition material affects the Si removal rate, with the scattering and sputtering properties playing a role in determining the removal change.