CAPACITIVE SURFACE MICROMACHINING ABSOLUTE PRESSURE SENSOR

摘要

PURPOSE: To ratio-measure absolute pressure by providing a pair of sensors causing the change of a capacity value between the first and second conductive sections of a capacitor in accordance with the inflection of a polycrystalline silicon diaphragm corresponding to pressure in a diaphragm cavity and the fluctuation of atmospheric pressure. CONSTITUTION: An absolute pressure sensor 100 measuring gas pressure such as the air pressure of an intake manifold and atmospheric pressure contains two air gap capacitors of two electrodes. A diaphragm electrode 20 which can move is constituted of polycrysallinve silicon, and the fixed electrode is formed in a substrate 30. The upper electrode 20 constitutes a diaphragm cavity 28 which is hermetically sealed by fixed pressure. A pressure difference between the diaphragm cavity 28 and the external part of the sensor inflects the upper electrode 20. The matched reference capacitor 200 which has a similar constitution and which is not sealed is formed for measuring a ratio and it has permeable polyimide sealing 276.