W-B-N diffusion barriers for Si/Cu metallizations

Abstract Reactively sputtered from a W 2 B target, amorphous W-B-N thin films are investigated. The physical properties of the films, namely density, resistivity, crystallization behavior and reaction temperature with silicon, are given as functions of composition. Additionally, the films are assessed as diffusion barriers between silicon substrates and copper overlays. By I ( V ) measurements of shallow-junction diodes, a 100 nm W 64 B 20 N 16 barrier prevents copper from reaching the silicon during an 800 °C, 30 min heat treatment in vacuum. W 79 B 21 films are able to prevent diffusion into the diodes only up to 500 °C. High resolution transmission electron microscopy shows that W 64 B 20 N 16 and W 79 B 21 films are both marginally amorphous with local ordering of less than 1.5 nm.