SENSOR AND METHOD FOR PRODUCING A SENSOR

Abstract

A sensor including a deformation body having a membrane for deformation when subjected to pressure from a medium. The sensor further includes a strain element applied to and attached to the membrane. The strain element is based on SOI technology and has multiple piezoresistive resistors.

Claims

1. Sensor comprising a deformation body having a membrane for deformation when subjected to pressure from a medium, a strain element applied to the membrane and fixed to the membrane, wherein the strain element is based on SOI technology and comprises a plurality of piezoresistive resistors.

2. Sensor according to claim 1, wherein the piezoresistive resistors are laterally exposed Si resistors.

3. Sensor according to claim 1, wherein the piezoresistive resistors each comprise a spatially exposed Si nanowire.

4. Sensor according to claim 1, wherein. a connecting means is arranged between the membrane and the strain element, and the strain element is fixed to the membrane via the connecting means.

5. Sensor according to claim 4, wherein the Young's modulus of the connecting means is at least as great as that of the membrane.

6. Sensor according to claim 4, wherein the connecting means comprises a glass solder or a metal solder or an inorganic adhesive or an organic adhesive.

7. Sensor according to claim 1, wherein the strain element covers a major part of the membrane.

8. Sensor according to claim 1, wherein the stretch element is connected to the membrane over a major portion of its lateral extent.

9. Sensor according to claim 1, wherein the strain element has a maximum thickness of at most 200 μm.

10. Sensor according to claim 1, wherein the deformation body comprises or consists of one or more of the following materials: glass, sapphire, silicon, steel, ceramic.

11. Sensor according to claim 1, wherein the piezoresistive resistors are arranged in an edge region of the membrane.

12. Method of manufacturing a sensor, comprising the steps: A) providing a deformation body with a membrane for deformation when subjected to pressure from a medium, B) providing a strain element, wherein the strain element is based on SOI technology and comprises a plurality of piezoresistive resistors, C) applying and fixing the strain element to the membrane.

13. Method according to claim 12, wherein the strain element is attached to the membrane via a direct bonding process.

14. Method according to claim 12, wherein the strain element is attached to the membrane via a connecting means.

Description

[0035] The figures show:

[0036] FIGS. 1 and 2: Embodiments of the sensor, each in cross-sectional view,

[0037] FIGS. 3 and 4: Embodiment example of the sensor in cross-sectional view and in plan view,

[0038] FIG. 5: Position in an embodiment example of the method for manufacturing the sensor.

[0039] FIG. 1 shows a first embodiment example of the sensor in a cross-sectional view. The sensor comprises a deformation body 1 with a membrane 10 and a support body 11. The membrane 10 is supported in edge regions by the support body 11. In an inner region of the membrane 10, the membrane 10 is not supported by the support body 11 and is freely oscillatable or freely bendable relative to the support body 11.

[0040] Presently, the membrane 10 and the support body 11 are formed in one piece, and consist, for example, of ceramic. However, it is also possible that the support body 11 and the membrane 10 are not formed integrally with one another and are made of different materials, for example.

[0041] A strain element 2 is arranged on a side of the membrane 10 facing away from the support body 11. The strain element 2 is a semiconductor chip based on SOI technology. The strain element 2 comprises a silicon substrate 22 and a SiO.sub.2 layer 21 on the silicon substrate 22. Laterally exposed piezoresistive resistors 20 made of silicon are arranged on a side of the SiO.sub.2 layer 21 facing away from the silicon substrate 22. The piezoresistive resistors 20 are electrically isolated from each other and also from the silicon substrate 22 by the SiO.sub.2 layer. On a side facing away from the silicon substrate 22, the piezoresistive resistors 20 are passivated by a passivation layer 23, for example of silicon nitride. The piezoresistive resistors 20 are electrically contacted via metallic conductor tracks 24.

[0042] During operation of the sensor, for example, the side of the membrane 10 facing away from the strain element 2 is brought into contact with a medium, for example a liquid such as oil or water. The pressure exerted on the membrane 10 by the medium causes the membrane 10 to bend, which also causes the strain element 2 to bend and the piezoresistive resistors 20 to become strained. This tension changes the resistance value of the piezoresistive resistors 20, which can be measured via the contacting through the conductor tracks 24. For example, the piezoresistive resistors 20 are connected to form a Wheatstone measuring bridge.

[0043] In FIG. 1, the strain element 2 is applied directly to the membrane 10 such that the silicon substrate 22 is in direct contact with the membrane 10. For example, the strain element is applied to the membrane 10 via direct bonding. The strain element 2 completely covers the membrane 10, in particular the unsupported part of the membrane 10. In this case, the strain element 2 is directly bonded to the membrane 10 along the entire lateral extent of the strain element 2.

[0044] FIG. 2 shows a second embodiment of the sensor. Here, the strain element 2 is constructed in exactly the same way as in FIG. 1, but unlike in FIG. 1, the strain element 2 is applied to the membrane 10 via a connecting means 3 and is connected to the membrane 10 via this connecting means. The connecting means 3 is, for example, a glass solder or a metal solder or an organic adhesive or an inorganic adhesive. The modulus of elasticity of the connecting means 3 is preferably at least as great as that of the membrane 10. In the present case, the membrane 10 consists, for example, of stainless steel.

[0045] FIG. 3 shows a third embodiment of the sensor in a cross-sectional view. Here, the piezoresistive resistors 20 each comprise a nanowire made of silicon. The nanowires are spatially exposed in such a way that the nanowires are unsupported and freely suspended above the silicon substrate 22, at least in regions. Thus, the SiO.sub.2 layer is removed in areas in the region below the nanowires so that the nanowires are not supported by the SiO.sub.2 layer there. As in the second embodiment, the strain element 2 is here again attached to the membrane 10 with the aid of a connecting means 3.

[0046] FIG. 4 shows a top view of the third embodiment of the sensor. It can be seen that the strain element 2 comprises four piezoresistive resistors 20 each with a nanowire. The piezoresistive resistors 20 are connected to each other via metallic conductor tracks 23 to form a Wheatstone measuring bridge.

[0047] FIG. 5 shows a position in an embodiment example of the method for manufacturing a sensor. Here, a strain element 2 based on SOI technology with several piezoresistive resistors 20 and a deformation body 1 with a membrane 10 are provided. The strain element 2 is applied to and attached to the membrane 10. Shown here is the case where the strain element 2 is applied directly to the membrane 10, for example by direct bonding. Alternatively, the strain element 2 could be attached to the membrane 10 using a connecting means.

[0048] The invention is not limited to the embodiments by the description based thereon. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the claims, even if these features or this combination itself are not explicitly stated in the claims or embodiments.

LIST OF REFERENCE SIGNS

[0049] 1 Deformation body

[0050] 2 Strain element

[0051] 3 Connecting means

[0052] 10 membrane

[0053] 11 support body

[0054] 20 piezoresistive resistor

[0055] 21 SiO.sub.2 layer

[0056] 22 silicon substrate

[0057] 23 passivation layer

[0058] 24 conductor track