Semiconductor pressure sensor connected to a support element

Abstract: A semiconductor pressure sensor (10) includes a substrate (12) as semiconductor material which comprises an active surface (14) for receiving integrated components (26, 28) and a rear side (16) in which to form a diaphragm (20) adjoining the active surface (14) and exposed to the press­ ure to be measured a recess surrounded by thick edge regions (22, 24) is formed. On the active surface (14) integrated components are provided which under the influence of mechan­ ical deformations of the diaphragm (20) vary one of their electrical parameters. The substrate (12) is connected to the support element (34) in the region of the active surface (14) surrounding the diaphragm (20) by using an elastomer seal (40). The diaphragm (20) is in communication from the rear side of the substrate (12) with a supply conduit (44) for the pressure to be measured.

Description: The invention relates to a semiconductor pressure sensor as defined in the pre-characterizing part of claim 1. From US-A-4,373,397 a pressure sensor is known having a diaphragm of silicon and including resistors disposed on the side of the pressure sensor subjected to pressure. A ring-shaped cylinder barrel extends about the periphery of the diaphragm and has a rear face cemented to a wall by an elastic plastic material. This pressure sensor does not have a separate support element having an opening therethrough for supporting the semiconductor substrate of the sensor. The invention is based on the problem of providing a semiconductor pressure sensor of the type mentioned at the beginning which is suitable for use at high pressures and the output signals of which are hardly influenced by form changes of the support element. According to the invention this problem is solved by the features of the characterizing part of claim 1. In the semiconductor pressure sensor according to the invention the connection to the support element is on the active surface of the substrate with interposition of an elastomer seal. This means that under the action of pressure on the diaphragm a force arises on the joint between the pressure sensor and the support element and makes the sealing action the greater the greater the pressure. An additional rigid clamping of the substrate to the support element is not necessary and consequently the desired independence from mechanical deformations of the support element is achieved. Advantageous further developments of the invention are characterized in the subsidiary claims. The invention will now be explained by way of example with reference to the drawing in which the pressure sensor according to the invention is illustrated in a sectional view with its features essential to the invention. The pressure sensor 10 illustrated in the drawing includes a semiconductor substrate 12 which has an active surface 14 and a rear side 16. Formed in the rear side 16 is a recess 18 so that a diaphragm 20 adjoining the active surface 14 is formed and is surrounded by thick edge regions 22, 24. Formed in the active surface 14 are integrated components, for example integrated resistors 26, 28, which on deformation of the diaphragm 20 likewise undergo a mechanical dimensional or shape change and vary one of their electrical parameters, in the example given their resistance. The electrical signals are supplied to and from the integrated components 26, 28 by means of bond wires 30, 32. The pressure sensor 10 is disposed in a support element 34 which is provided with an opening 36 of which the inner peripheral surface forms a step 38. The pressure sensor 10 is adhered to the step 38 of the support element 34 with interposition of an elastomer seal 40. The adhesive action results from the adhesion force active between the materials involved. As material for the elastomer seal for example silicone rubber, butyl rubber or also nitrile rubber may be used. Any other material with comparable properties can of course be employed. The support element 34 is mounted in turn in a housing 42 which has an opening 44 for introduction of the pressure to be measured. As apparent in the drawing the pressure acts on the face of the diaphragm 20 facing the rear side of the pressure sensor 10. As a result, the pressure acting generates a force which intensifies the sealing action of the elastomer 40 to an extent which is greater the higher the pressure. Because of its special mounting the pressure sensor 10 can therefore be employed for high pressures. For mechanical uncoupling between the support element 34 and the pressure sensor 10 a depression 46 surrounding the diaphragm can be formed in the active surface of the substrate 12 in the region between the diaphragm 20 and the connecting region to the support element 34. In this manner, mechanical deformations caused by temperature changes in the support element are prevented from causing deformations of the diaphragm 20 which would result in a falsification of the measurement result. This mechanical decoupling effective in addition to the use of the elastomer seal 40 permits hysteresis-free measurement results which are very extensively free from temperature influences. If a further mechanical decoupling is desired a plurality of depressions similar to the depression 46 may be formed in the thick edge regions 22, 24 of the substrate. Formation of such depressions from the rear side of the substrate 12 is also possible. In the drawing the pressure sensor 10 is indicated only schematically; it need not be particularly shown how electrical signals are supplied and carried away because this is not essential to the invention.

Claims: A pressure sensor comprising: a substrate (12) of semiconductor material having first and second major surfaces, said semiconductor substrate being provided with a recess in the second major surface thereof extending toward the first major surface so as to define relatively thick peripheral edge regions (22, 24) bounding the recess and a relatively thin pressure-sensitive diaphragm (20) extending between said relatively thick edge regions and connected thereto, a support element (34) on which said semiconductor substrate is mounted and supporting said semiconductor substrate at the relatively thick peripheral edge regions of said semiconductor substrate, elastomeric means (40) interposed between said support element and the relatively thick peripheral edge regions of said semiconductor substrate and providing a seal between said support element and said semiconductor substrate at the relatively thick peripheral edge regions of said semiconductor substrate, at least one integrated component (26, 28) provided on said first major surface of said semiconductor substrate, the relatively thin pressure-sensitive diaphragm of said semiconductor substrate being responsive to pressure incident thereon to undergo mechanical deformation, and said at least one integrated component having an electrical parameter subject to variation in response to mechanical deformation of said pressure-sensitive diaphragm under the influence of pressure, the variation in the electrical parameter of said at least one integrated component being proportional to the magnitude of the mechanical deformation of said thin pressure-sensitive diaphragm so as to be indicative of a measurement of a pressure to which said relatively thin pressure-sensitive diaphragm is exposed; characterized in that said support element (34) has an opening (36) therethrough and provides an inner peripheral support (38) surface in opposed relation to the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate, said elastomeric means (40) is interposed between said inner peripheral support surface of said support element and the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate so as to provide a peripheral seal between said inner peripheral support surface of said support element and the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate, said at least one integrated component (26, 28) being provided in a relatively thick edge of said semiconductor substrate adjacent to said pressure-sensitive diaphragm, the second major surface of said semiconductor substrate being free of obstruction and positioned for exposure to pressure introduced into the opening through said support element, the relatively thin pressure-sensitive diaphragm of said semiconductor substrate being disposed in the opening through said support element and being responsive to pressure introduced into the opening through said support element and entering the recess provided in the semiconductor substrate to undergo mechanical deformation, and the sealing action of said elastomeric means between said inner peripheral support surface of said support element and the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate increasing in response to the introduction of the pressure being measured into the opening through said support element and through the recess provided in said semiconductor substrate to impinge upon the relatively thin pressure-sensitive diaphragm of said semiconductor substrate. A pressure sensor as set forth in claim 1, further characterized in that said support element is provided with a counterbore to define a shoulder along the inner periphery thereof at the juncture between the opening and the counterbore and extending outwardly from the opening for providing said inner peripheral support surface to which the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate is in opposed relation with said elastomeric means interposed therebetween. A pressure sensor as set forth in claim 2, further including a housing (42) defining a chamber in which said support element is fixedly mounted, and further characterized in that said housing has an input port (44) in registration with the counterbore and the opening in said support element and the recess provided in said semiconductor substrate for introduction of the pressure to be measured. A pressure sensor as set forth in any of claims 1-3, further characterized in that mechanical decoupling means are provided between said support element and said relatively thin pressure-sensitive diaphragm of said semiconductor substrate for preventing mechanical deformations in said semiconductor substrate caused by temperature changes in said support element from causing mechanical deformations of said relatively thin pressure-sensitive diaphragm. A pressure sensor as set forth in claim 4, further characterized in that said mechanical decoupling means comprises a depression (46) formed in said relatively thick peripheral edge regions of said semiconductor substrate and surrounding said relatively thin pressure-sensitive diaphragm, said depression opening onto the first major surface of said semiconductor substrate and being disposed between said relatively thin pressure-sensitive diaphragm and said elastomeric means providing the peripheral seal between the first major surface at the relatively thick peripheral edge regions of said semiconductor substrate and said inner peripheral support surface of said support element. A pressure sensor as set forth in claim 5, further characterized in that said depression is disposed inwardly with respect to said inner peripheral support surface of said support element for isolating said relatively thin pressure-sensitive diaphragm of said semiconductor substrate from mechanical deformations in said support element caused by temperature changes in said support element. A pressure sensor as set forth in any preceding claim, further characterized in that said elastomeric means is made of a material taken from the class including silicone rubber, butyl rubber and nitrile rubber.

Inventors: LIEBGEN MANFRED H, LIEBGEN, MANFRED H
Applicants: TEXAS INSTRUMENTS DEUTSCHLAND, TEXAS INSTRUMENTS DEUTSCHLAND GMBH
Application year: 1990
Main classification: G01L9
IPC codes: H01L29, G01L9