Impurity-controlled Mo films as diffusion barriers for Cu metallization

Abstract

Effects of vacuum conditions on the oxygen content and microstructure of Mo layers used with Cu gate lines as thin-film transistor-liquid crystal display diffusion barriers were investigated. Mo was deposited using ion-beam sputtering at 1.0 x 10(-5) and 7.0 x 10(-7) Torr. The Mo layer oxygen content and the microstructure and changes in chemical composition of the Cu/Mo/SiO2/Si layer during annealing were examined. The Mo layer microstructure was influenced by oxygen; increasing concentration increased the energy required for secondary grain growth. Growth was suppressed at high oxygen levels. Therefore, diffusion barrier performance is enhanced by finer Mo layer grain sizes.