Silicon micromachined sensor for gas detection

The paper presents the layout and the technological steps for an interdigitated integrated capacitor used for gases detection. Silicon micromachining technology is applied for manufacturing the sensor substrate. The sensitive layer used is phthalocyanine (Pc) deposed by evaporation technique under high vacuum. The phthalocyanine derivatives are obtained by the same deposition technique. Considering the different sensitivities of phthalocyanines derivatives, we obtained different gas sensors. The copper phthalocyanine (CuPc), nickel phthalocyanine (NiPc) and iron phthalocyanine (FePc) have been investigated for NO_x detection. The measurement of sensors for NO_x and NO₂ detection will be presented as gas concentration versus impedance. The microsensors testing structures deposited with phthalocyanines were investigated by impedance measurements in a vacuum chamber controlled by a gas analyser. The measurements were made at room temperature but a medium temperature is applied (<200 °C) after measurement, for cleaning the material in order to reuse the sensor. The sensor is integrated, MOS compatible, cheap, easy to be used and has a low power consumption.