Chemical gas sensor

• Main Authors: FAU, PIERRE, ALEPEE, CHRISTINE
• Format: Patent
• Language: English; French; German
• Published: 08.01.2003
• Edition: 7
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

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. L'invention concerne un capteur chimique de gaz à semi-conducteur comportant: un cadre (10) en matériau semi-conducteur, définissant une fenêtre rectangulaire (12) ayant deux axes de symétrie orthogonaux, une couche diélectrique (14) déposée sur cadre, une couche conductrice (18), formant corps de chauffe, déposée sur la couche diélectrique et percée d'une ouverture centrale (24), une couche isolante (26) déposée sur la couche conductrice, un élément sensible (40) déposé sur la couche isolante et recouvrant l'ouverture centrale de la couche conductrice, et deux pistes conductrices (28) couplées aux extrémités respectives de la couche conductrice. Ce capteur est caractérisé en ce que la couche conductrice (18), possédant les mêmes axes de symétrie que la fenêtre du cadre, a la forme d'un papillon, avec une partie centrale (20) comportant ladite ouverture (24) et deux ailes latérales identiques (22) allant en s'élargissant de la partie centrale pour se terminer à proximité du cadre.