Surface treatment process using photoemission-assisted plasma for achievement of atomic scale flattened surface

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Photoemission-assisted plasma (PAP) ion source has been developed for flattening surface morphology of metal substrates down to an atomic-scale roughness. In this study, ion kinetic energy (Ek) of impinging on surface was estimated by Langmuir probe measurement, resulting in Ek of PAP with 0.1-30 eV. PAP irradiations to Cu-deposited Si substrates with Ra(0) of ~13 nm were conducted in low energy (< 30 eV) and changing ion fluence (< 1018 cm-2) regime. From the surface analysis by atomic force microscopy, surface roughness were reduced down to 15~70% compared of Ra(0). However, protrusions formed on the surfaces due to high ion fluence irradiation, which caused increase of surface roughness. The experiment conditions that control the surface morphology changes are revealed from the aspect from ion energy and ion fluence. Based on the observations, it is considered that surface migration enhancement of surface atoms induced by low Ek of PAP plays a vital role for the morphology changes.