Phase separations of amorphous CoW films during oxidation and reactions with Si and Al

摘要

Reactions of thin Co55W45films in contact with Si(100) substrates and aluminum overlayers annealed in vacuum in the temperature ranges of 625–700 °C and 500–600 °C, respectively, and of thin Co55W45films in air from 500 to 600 °C were investigated by Rutherford backscattering spectrometry, glancing angle x‐ray diffraction, and scanning electron microscope techniques. CoW alloy films were amorphous and have a crystallization temperature of 850 °C on SiO2substrates. The compound formed is Co7W6. Phase separations were found in all the reactions. A layer of cobalt compounds (CoSi2in Si/CoW, Co2Al9in CoW/Al, and Co3O4in CoW with air) was found to form at the reaction interfaces. In addition, a layer of mainly tungsten compounds (WSi2in Si/CoW, WAl12in CoW/Al, and WO3in CoW with air) was found next to cobalt compound layers, but further away from the reaction interfaces. The reactions started at temperatures comparable to those required for the formation of corresponding tungsten compounds.