Capacitive semiconductive sensor with hinged diaphragm for planar

Abstract

A semiconductive sensor or transducer (100), for example, a pressure sensor utilizing capacitance variations to sense pressure variations, of the silicon-on-silicon type, in which a 'hinge' (111A) in the form of a relatively thin, encircling area is provided at the outer peripheral edge of the diaphragm, causing the central region (117) of the diaphragm (111) to move in a linear, non-curved or planar manner (compare FIG. 2 to FIG. 1), providing a linear response or frequency output. A first embodiment (FIG. 3) of the hinged silicon-on-silicon capacitive pressure sensor, which is basically cylindrical in shape, has the hinge formed by etching, milling or machining away some of the thickness of the diaphragm at its outer peripheral edge. In a second embodiment (FIG. 4) the hinge is formed by etching away some of the thickness of the diaphragm at its outer peripheral edge and using a glass layer to control the etching using a selective chemical enchant which is selective for silicon but does not attack the glass; while a third embodiment (FIG. 5) uses aluminum in place of the glass. In a fourth embodiment (FIG. 6) the hinge is formed effectively on the opposite side of the diaphragm from the shown in the embodiments of FIGS. 3-5. The hinge structure can be used in other forms of semiconductive transducers, which use the relative movement of a semiconductive diaphragm with respect to another semiconductive layer or substrate.