Approaches to diffusion barrier creation and trench filling for copper interconnection formation

Abstract

The technique of copper filling of trenches which is based on the effect of the melting temperature decrease, depending on film thickness reduction, has been proved and demonstrated experimentally. An approach to diffusion barrier creation is proposed. Ta-W-N amorphous alloy has been selected as the barrier material for copper. This barrier layer keeps its properties in the Cu/Ta-W-N/TiSi₂/Si structure up to 800 °C, and in the Cu/Ta-W-N/SiO₂ structure up to 850 °C. The temperature for copper filling of the trenches is shown to be significantly lower than the temperature of bulk copper melting, and to depend on the thickness of the film. It is determined that this effect is caused not only by the lowering of the phase changing temperature as a result of the thinning of the film, but also by the system tendency to optimize its form by the change in the ratio of the surface and volume energies. When the thickness is 50 nm the temperature of filling is 750 °C, when it is 100 nm – 850 °C. However, this temperature reduction is not enough for use of the presented approach in UVLI technology, and further development of this approach is required, including possible combination with other filling methods.