UK scientists have made thin films that could help to make electronic devices faster and smaller.

Claire Carmalt's group at University College London, in collaboration with the manufacturing chemicals producer, SAFC Hitech in Bromborough, used chemical vapour deposition (CVD) to produce thin films of tungsten carbonitride from new precursor materials.

Today's society demands faster and higher capacity electronic devices such as computers, calculators and mobile phones. To improve these gadgets, their circuitry must be reduced in size. The barrier layer, which can be made from tungsten carbonitride, is a key component of electronic circuits. It prevents the circuit degrading by stopping copper diffusion from the circuit's wires into the semiconducting silicon components. To reduce the circuit's size, this barrier layer must be made smaller and CVD can help by allowing scientists to deposit the layer over smaller areas.

Carmalt's group investigated a range of tungsten imido complexes to produce precursors with ideal thermal properties for CVD. They successfully tuned the ligands surrounding the tungsten centre to optimise the thermal properties of the precursors to produce tungsten carbonitride thin films. The films produced by the team were uniform, adhesive, hard and resistant to scratching with a steel scalpel.

'By studying the thermal properties of the precursors, we get an idea of how they decompose and so what conditions we need to get film deposition,' says Carmalt. 'It also gives us an idea of their stability and hence what their shelf-life would be for potential industrial applications.'

George Koutsantonis, an expert in CVD from the University of Western Australia, Perth, comments that this work 'demonstrates the clear advantages that chemists have with their structured approach to materials synthesis'.

Ruth Doherty