INTEGRATED GAS FLOW SENSOR BASED ON POROUS SILICON MICROMACHINING

摘要

The device of the integrated gas flow sensor is fabricated on a membrane made of a bilayer of SiO2 / polysilicon on bulk crystalline silicon. The membrane is either suspended on a deep cavity formed on bulk crystalline silicon, or it is lying on a thick oxidized porous silicon layer. The cavity under the membrane is fabricated by bulk silicon micromachining using porous silicon as a sacrificial layer. The sensing element is composed of a two series of integrated thermocouples on the left and right side of a heated resistor. The thermocouples are composed of parallel strips of aluminum/p-type polysilicon or p-type polysilicon, in contact on one end. A second polysilicon resistor outside the membrane in series with the heated resistor serves to stabilize the heating power to better than 0.05%.