Diffusion barrier and electrical characteristics of a self-aligned MgO layer obtained from a Cu(Mg) alloy film

Diffusion barrier characteristics and electrical properties of self-aligned MgO layers obtained from a Cu(Mg) alloy film have been investigated. Self-aligned surface and interfacial MgO layers were formed upon annealing a Cu(Mg) film in an oxygen ambient and prevented interdiffusion of Cu in SiO2 up to 700 degrees C. The thermal stability of a pure Cu/TiN/Si multilayer system has been significantly enhanced up to 800 degrees C by the MgO layers by forming a MgO/Cu/MgO/TiN/Si multilayer system. A combined structure of Si3N4(500 Angstrom)/MgO(100 Angstrom) increased the breakdown voltage up to 20 V from 15 V and reduced the leakage current density down to 3x10(-9) A/cm(2) from 1x10(-8) A/cm(2) compared to a pure copper system. Consequently, the deposition of Cu(Mg) alloy followed by annealing in an oxygen ambient gives rise to the formation of a self-aligned MgO layer with excellent diffusion barrier and electrical characteristics and the film can be applied as a gate electrode in thin-film transistor/liquid-crystal displays, resulting in a reduction of process steps. (C) 2000 American Institute of Physics. [S0003-6951(00)02940-5].