ИСТИНА

In modern microelectronic technology, the transition to the atomic scale era requires localizing ions’ impact within one atomic layer. This could be achieved through application of ions with energies to be of the order of atoms’ binding energy (5-50 eV) into manufacturing process as, for example, PEALE (Plasma Enhanced Atomic Layer Etching) [1,2] and PEALD (Plasma Enhanced Atomic Layer Deposition) [3,4]. Nevertheless, there is a sufficiently extensive set of data on the sputtering of different materials by different types of ions [5] at present, there are almost no reliable and sufficiently correct data on ion sputtering yield (is the probability of a target atom to leave the surface per coming ion with kinetic energy) at ion energies below 100 eV, even for such important materials for microelectronic applications as Si and SiO2. In this work, the sputtering of thin films of amorphous Si and SiO2 by low-energy Ar+, Kr+, and Xe+ ions in the range of 20–200 eV was studied in low-pressure ICP plasma in pure Ar, Kr, and Xe, respectively. Sputtering rate measurements were made in-situ with a laser ellipsometer, while various plasma diagnostics were used to accurately determine the composition, energy spectrum, and ion flux onto a sample surface. The surface modification of Si films during sputtering was determined by ex-situ surface diagnostics: vacuum Atomic Force Microscopy (AFM) and angular X-ray Photoelectron Spectroscopy (XPS). It was shown that sputtering still preserves at ion energies below the kinetic sputtering threshold. However, the yields on ion energy dependencies drastically changes at the energy of about 75 eV (fig. 1). The AFM analysis shown, that low energy spattering causes a significant decrease of the samples’ roughness. The XPS data demonstrated, that even 200 eV ions able to penetrate rather deep into the materials, producing highly damaged and, thus, abounding vacant chemical bounds top layer, and accumulating at a depth of 3-4 nm from the surface.