Due to the high conformality, excellent thickness control, availability of dense and pinhole free films of different materials at low deposition temperature and low cost, atomic layer deposition (ALD) can be a selected technique for the integration of new materials into MOEMS and MEMS devices.
Actually, ALD coatings can improve wear and corrosion resistance, prevent moisture-induced adhesion, facilitate charge dissipation and functionalize the surface of the devices. We use ALD for the fabrication of protective, transparent dielectric layers for the reflective surface of metallic mirrors included in MOEMS devices.
By the precise thickness control and modeling of the optical reflectivity, we can engineer dielectric stacks that not only protect the reflective surface, but also produce an enhanced reflectivity in selected spectral regions. In collaboration with STMicroelectronics, the optimized dielectric stacks are integrated and tested in real MOEMS devices.
Several challenges are expected due to the different applications of micromirrors inside MOEMS devices that can require enhanced reflectivity in different spectral regions.
The scientific approach consists on the development and optimization of the ALD process, the characterization of the film in terms of chemical, morphological structural and optical properties by means of a variety of experimental tools, to maximize the knowledge of the materials characteristics.
This activity has the potentiality of a quick industrial transfer, with TRL 3-6, but also paves the way towards the integration of other ALD-deposited oxides into MEMS devices, aiming at different functionalities (TRL 2-4). For instance nanostructured oxides can be imagined to be implemented inside portable gas sensing devices, and some seed experiments are planned in collaboration with IMM-BO.
This activity is developed in collaboration with STMicroelectronics, Agrate Brianza, and with Università di Bologna. Discussions within the framework of the LAB4MEMSII project (30 European partners) help in improving the knowledge.