Efficient integration of nanomaterials on microfabricated platforms by suspersonic cluster beam deposition

In spite the high level of complexity reached by micromachining in silicon technology, the integration of functional nanomaterials into micro electro mechanical systems (MEMS) is still an open issue. This is basically due to the mechanical and thermal fragility of silicon microstructures and metallizations, as well as on difficulties related to nanomaterial patterning in batch deposition for large-scale production of devices. Here we demonstrate the use of novel gas-phase deposition method based on supersonic cluster beams to integrate nanostructured oxide films as active elements in silicon microstructures for batch production of conductimetric chemical microsensors. Supersonic cluster beam deposition (SCBD) process is scaleable, it allows the deposition of nanoparticles with low kinetic energy on substrates kept at room temperature, and it can be coupled with hard mask patterning with sub-micrometric lateral resolution, for a wide range of nanomaterials. We used clusters beams produced by a Pulsed Microplasma Cluster Source (PMCS) and by Flame Beam Source (FBS) for the fabrication of chemical microsensors batches based on two different types of suspended silicon parts: microhotplates and microbridges. Hybrid micro-devices coupling on the same silicon platform the chemical detection to the physical measurement of the gas flow were also produced. Sensing performances of the devices were characterized respect to several compounds including ethanol vapors, NO2, and hydrogen, while hybrid devices were characterized carrying out at the same time either the physical measurement of the air flow flushing on them, and the detection of chemicals transported by the air flow. These results demonstrate the direct and high-throughput parallel integration of nanomaterials on complex MEMS, indicating the possibility of using SCBD also for micro-cantilever and microfluidic devices functionalization, gas-getters incorporation in MEMS, and a generally wider use in the development of innovative microsystems based on the nano-on-micro approach