Progressive process technology for new MEMS and NEMS devices
Medium-resistant protective layers for sensors, optical coatings, high capacity trench capacitors, new NEMS devices for gas sensors, biosensors with nanowires, ultrathin freestanding membranes: All of this is possible with modern ALD technology (Atomic Layer Deposition).
ALD is a deposition process which is based on the chemical surface reaction of at least two precursors. The process allows for a layered increase of high-quality layers with thicknesses in the range of 1-100 nm. A steadily increasing selection of ALD materials enables new, innovative sensor applications. Within the framework of the Forschungsfabrik Mikroelektronik Deutschland (FMD) Fraunhofer IMS acts as an ALD competence center. At Fraunhofer IMS we offer the ALD technology for 200 mm wafers.
Application area of ALD technology
Because the process temperature during ALD deposition is low in comparison to conventional CVD processes, ALD layers can be deposited on substrates with integrated circuits in particular, i.e. on CMOS wafers. Therefore, the ALD technology can be applied for different MEMS, NEMS or CMOS-related applications, for example:
Cost-efficient 3D NEMS technologies for the generation of freestanding nanostructures on CMOS surfaces with a high reproducibility have been developed and patented by Fraunhofer IMS.
Medium-resistant layers for sensor applications, for example for pressure sensors or the encapsulation of medical implants. Aluminum oxide (AI2O3) and tantalum pentoxide(Ta2O5) are available for ALD passivation. Further ALD materials can also be implemented at Fraunhofer IMS, if required.
Electrical or optical shields can be manufactured through metallic layers like ruthenium (Ru). Moreover, ALD layers can be used as transparent, conductive electrode layers, for example for optical sensors or solar cell applications.
Due to the high conformity of the ALD process, dielectrics can be used as an ideal isolation in trench capacitors. For trench capacitors there are high- and medium-k dielectrics available. Fraunhofer IMS has experience in the development of trench capacitors for high-temperature applications (more than 250 °C) on the basis of ALD layers.
The ALD technology offers the option to realize freestanding 3D MEMS or NEMS structures with wall thicknesses in the nanometer range on CMOS surfaces. The combination of different ALD materials allows the exact configuration of the physical and chemical parameters of the freestanding structure. Due to the nanoscale wall thickness and the low mechanical and thermal mass, the 3D structures are perfectly suited for progressive sensor application in gas and bio sensor systems. Furthermore, nanowire, ultrathin membranes and cantilevers can be manufactured at Fraunhofer IMS using ALD technology.
Special solutions for the arbitrarily shaped devices, for example packaged sensors or coatings with special materials can be realized upon request.