Micromachined photonic integrated circuits for sensor applications - Experimental results

The paper presents the integration on the same chip of: Mach - Zehnder interferometers and Y junctions based on SiON waveguides, 3D movable micromechanical structures (diaphragms and cantilevers), optical couplers and photodetectors for optical read-out. The SiON low loss optical waveguides were fabricated by LPCVD processes, compatible with CMOS technology. The diaphragms, used for pressure sensing, obtained by p(+) etch stop techniques, were placed under the sensing arm of the interferometer. The cantilevers, used in micromechanical resonators were manufactured by front side micromachining. The optical waveguides were coupled with different types of photodetectors, for optical read-out. Also experiments for hybrid integration of an emitting device have been performed. We used an AlGaAs emitting diode (lambda(p) = 628 nm), with high edge emission, mounted in a silicon groove, on the same wafer with the sensor. The lateral emitted light is coupled in the waveguide. One of the main problems that had to be solved will be the matching of all the involved technologies. The result of our research is the demonstration of the compatibility between the technological processes involved and the possibility of integration on the same silicon substrate of different components: waveguides, photodiodes, emitting devices, 3D movable microstructures in order to realize intelligent microsensors.