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Layers manufactured by the ALD technique have many interesting applications in microelectromechanical systems (MEMS), for example as protective layers for biocompatible coating, high-dielectric-constant layers, or low-temperature conformal insulating layers. Before an ALD process can be successfully implemented in MEMS processing, several practical issues have to be solved, starting from patterning the layers and characterizing their behaviour in various chemical and thermal environments. Stress issues may not be forgotten. We have recently implemented two ALD processes, namely the trimethylaluminium/water process to deposit Al2O3 and the titanium tetrachloride/water process to deposit TiO2 in our MEMS processing line and carried out the necessary characterization, details of which are reported here. For us, ALD has been a truly enabling technology in the processing of a three-dimensional micromechanical compass based on the Lorentz force, where Al2O3 acted as a pinhole-free electrical insulation grown at low temperature.

The thermal stability of reactively sputtered tungsten–nitrogen alloy thin films is investigated for the application as diffusion barriers in silicon contact metallizations. The composition of W–N barriers is varied over a wide range including pure W. Aluminum, gold, and silver are used as low resistivity overlayers. Metallurgical interactions at temperatures ranging from 500 to 900 °C are studied. Incorporating nitrogen into tungsten advantageously stabilizes all three systems. The overall failure takes place rapidly above critical temperatures that depend on both the metal overlayer and the microstructure of the barrier. In some cases, W–N alloys can effectively prevent interdiffusion at temperatures as high as 800 °C for 30 min.