Sub-Micron-Wide surficial trench frames to define the coating areas of sensitive layers on silicon mems resonant chemical sensors

We propose a new processing method to form thin films on the predefined micro-areas of movable parts of microdevices by using trench frames on the device surfaces in the coating of solutions containing the membrane materials. We fabricated 500-nm-wide surficial trench frames additively on silicon microcantilevers to define the areas coated with the thin films by increasing the tolerance to protrusion of a liquid droplet from the edge in the coating process. The trench frames were fabricated on the silicon surfaces by deep-reactive ion etching with the resist mask patterned by electron beam lithography. We also fabricated the same trench frames on planar silicon substrates, and we examined the proper conditions for the formation of polybutadiene (PBD) thin films on the framed surfaces by coating PBD solution using a microdispenser system. When the n-dodecane solution of PBD was applied to the micro-area framed by the trenches, PBD film was successfully defined within the framed area. The trench frames fabricated on the cantilevers indicated the practical effectiveness to define the PBD thin films within the framed micro-areas.