Film deposition and buried layer formation by mass-analyzed ion beams

Abstract

We have developed ion-beam equipment which can produce metal ions in the energy range from very low energy (less than 10 eV) to high energy (400 keV). High-energy neutrals and secondary electrons which would be extremely harmful in low-energy experiments are removed from the beam. With this equipment, metallization of Si by low-energy ion beam deposition and by high-energy ion implantation has been performed. Film formation mechanisms and properties of deposited films were studied in the case of a low-energy Pd ion beam. The optimum ion energy, in terms of the collection efficiency and the condition of the film-substrate interface, was found to be 50–100 eV. Films with resistivity of the same order as that of the bulk material, and as thin as a few nanometers were obtained. It was confirmed by transmission electron microscopy that these films were already continuous and covered the entire substrate surface. In the case of metallization by high-energy ions, Pd, Ag, and Al ions were implanted into Si. It was found that a buried conductive layer is obtained only when concentration of implanted species exceeds a certain threshold. The buried PdSi layer formed by 320-keV Pd implantation at a dose level of 2.0 × 10 17 cm −2 had sheet resistance on the order of a few ohms and was stable under 800°C, 30 min anneal. Crystallinity of the implanted Si substrate surface was recovered after 600–800°C, 30 min anneal.