Chemical gas sensor

摘要

A dielectric layer, a conducting heater layer (18) with a central hole (24), an insulating layer and a sensitive element (40) are deposited on a semiconducting base containing a rectangular window with two axes of symmetry. The conducting layer is a butterfly shape with the same axes of symmetry, with a central part (20) and two identical side wings (22) extending to end near the base A sensitive element is deposited on an insulating layer and covers the central hole in a conducting layer, and two conducting strips (28) are coupled to the ends of the conducting layer. The central part of the conducting layer is rectangular with its length and width approximately half that of the window. The wings are as long as the window, ending over the base or over the window but near the base. The window is ca. 1 mm long and 0.75 mm wide. The sensitive element covers half of the surface of the central part of the conducting layer. The conducting strips extend to the ends of the wings. The central hole in the conducting layer is a square approximately 100 microns m along each side. The base is a monocrystalline silicon and the conducting layer is a polycrystalline silicon made conductive by doping. The sensitive element is made of a layer of metal oxide in the form of powder agglomerated with a porous structure, comprising spherical particles with a diameter of the order of 20 nm. Alternatively, the sensitive element has a lower layer of metal oxide with grains of between 100 nm and 1 microns m and an upper layer comprising spherical particles with a diameter of the order of 20 nm. The oxide is tin dioxide.