MEMS sensor, especially pressure sensor, for metrological registering of a measured variable

1. A MEMS sensor for metrological registering of a measured variable, comprising:

a plurality of layers arranged on one another, wherein:

said plurality of layers include at least one inner layer, which is arranged between a first layer and a second layer, and

in said inner layer there is provided extending perpendicularly to the plane of said inner layer through said inner layer at least one annular cavity, on which borders externally and forming a connecting element, a region of said inner layer, which is connected with said first layer and said second layer, and which surrounds said cavity annularly; said connecting element in the region of said inner layer is isolated by said cavity completely from an additional region surrounded by said cavity; and

a lateral surface of said connecting element externally bordering said cavity has in an end region facing said first layer a rounding decreasing the cross sectional area of said cavity in the direction of said first layer, and has in an end region facing said second layer a rounding decreasing the cross sectional area of said cavity in the direction of said second layer;

wherein layers adjoining one another are connected either directly with one another or via a connecting layer provided between the two adjoining layers, and

wherein said connecting layers have a layer thickness small in comparison with the layer thickness of the layers adjoining one another, and the layers adjoining one another have especially a layer thickness of greater than or equal to several 10s of μm.

2. A MEMS sensor as claimed in claim 1 , wherein:

at least said one inner layer has, surrounded by said cavity, at least one additional region, which is connected with said first layer or said second layer, and which borders on said cavity extending perpendicularly to said one inner layer through said one inner layer; and

said at least one additional region has a lateral surface at least sectionally internally bordering said cavity, in which lateral surface the end region facing the layer connected with said at least one additional region has a rounding decreasing the cross sectional area of said cavity in the direction of the layer connected with said at least one additional region.

3. The MEMS sensor as claimed in claim 1 , wherein:

said connecting element surrounds said cavity externally on all sides.

4. The MEMS sensor as claimed in claim 1 , wherein:

said inner layer includes at least one additional region, especially an additional region serving as an electrode.

5. The MEMS sensor as claimed in claim 1 , wherein:

the MEMS sensor is a pressure sensor, especially an absolute pressure, a relative pressure or a pressure difference sensor;

said first layer comprises a measuring membrane; and

said first layer is connected with a platform to enclose a pressure chamber, and said platform comprises said inner layer and said second layer.

6. The MEMS sensor as claimed in claim 5 , wherein:

said inner layer is connected with said first layer via a first connecting layer; and

said first connecting layer has a cavity exposing said measuring membrane and forming a pressure chamber.

7. The MEMS sensor as claimed in claim 5 , wherein:

said inner layer includes at least one additional region serving as an electrode, especially an additional region surrounded by an isolation moat;

said inner layer is connected with said second layer via a second connecting layer embodied as an insulation layer;

said electrode is connected with said second layer via said second connecting layer; and

said electrode is spaced from said first layer serving as a counterelectrode thereto.

8. The MEMS sensor as claimed in claim 5 , wherein:

said platform has, extending through said platform, a passageway, which communicates with the pressure chamber.

9. The MEMS sensor as claimed in claim 5 , wherein:

on a side of said first layer lying opposite said platform a further platform, especially an equally constructed further platform, is provided, which is connected with said first layer to enclose a pressure chamber.

10. The MEMS sensor as claimed in claim 1 , wherein:

the rounded end regions have, selected as a function of the layer thickness of said inner layer, a radius of curvature, which is greater than or equal to 1 μm, especially greater than or equal to 5 μm, especially greater than or equal to 10 μm.

11. A method for manufacture of a MEMS sensor as claimed in claim 1 , wherein said cavity is produced by a combination of an anisotropic etching method and an isotropic etching method.

12. The method as claimed in claim 11 , wherein:

by means of an anisotropic etching method especially by means of deep reactive ion etching (DRIE), a furrow with side walls extending essentially perpendicularly to the inner layer, is produced in the inner layer, the furrow extends to a predetermined etching depth into the inner layer but does not completely pierce it; and

by means of an isotropic etching method, especially by means of reactive ion etching (RIE), the cavity extending through the inner layer is produced from the furrow.

13. The method as claimed in claim 12 , wherein:

the etching depth is predetermined as a function of a layer thickness of the inner layer in such a manner that a difference between the layer thickness of the inner layer and the etching depth corresponds to a radius of curvature of the rounded end regions to be produced.