Deposition of cobalt disilicide thin films by laser ablation of cast targets

Abstract

Targets of pure cobalt silicide cast from the liquid state by vacuum metallurgical techniques are used for the deposition of cobalt disilicide films by laser ablation. The modes and conditions of cast target evaporation which ensure the preparation of stoichiometric cobalt disilicide films are studied. It is shown that the electrical resistivity of the films depends strongly on the substrate temperatures. The decrease in resistivity is extremely sharp in the temperature range 100–500 °C, wherein the resistivity drops from 800 to 60 μΩ cm. The dependence of the resistivity on the substrate temperature is relatively weak in the range 600–800 °C, where it falls to 30 μΩ cm. Grazing incidence X-ray diffractometry and Rutherford backscattering of helium ions are used to investigate the phase and elemental composition of the films. It is shown that at a substrate temperature of 400 °C all the films consist of stoichiometric CoSi 2. At other substrate temperatures the films contain a small amount of a second phase, either cobalt (mono) silicide or silicon depending on the substrate temperature.