Micromechanical sensor system

Abstract

A micromechanical sensor system that includes a mass that is deflectable at least in the z direction. A stop element having an elastic design is situated on the mass on at least one of the sides oriented in the z direction, via a connection element.

Claims

1. A sensor system, comprising: a mass that is deflectable at least in the z direction; a connection element that is joined to a thin layer; and multiple stop structures that are at least partially elastic and situated on a side of the thin layer facing away from the mass and oriented in the z direction, wherein a recess is situated between the mass and the thin layer, wherein the multiple stop structures have, at least in the z direction, different rigidities.

2. The sensor system as recited in claim 1, wherein the connection element is in the form of a connecting layer.

3. The sensor system as recited in claim 1, wherein the stop element includes a thin layer made of silicon.

4. The sensor system as recited in claim 3, wherein the thin layer includes: at least one recess and/or at least one hole and/or at least one elevation relative to a portion of the thin layer.

5. The sensor system as recited in claim 4, wherein at least two recesses included in the thin layer and/or at least two holes included in the thin layer are arranged in a periodic and/or symmetrical manner.

6. The sensor system as recited in claim 1, wherein the multiple stop structures in at least one direction along the thin layer have an increasing extension in the z direction.

7. The sensor system as recited claim 1, wherein the multiple stop structures having a high rigidity are situated in areas of the thin layer that are joined to the connection element.

8. The sensor system as recited in claim 1, wherein the multiple stop structures are asymmetrically situated on a thin layer.

9. The sensor system as recited in claim 1, wherein the connection element is U-shaped and is situated on two opposite sides of the thin layer, respective corners being rounded.

10. The sensor system as recited in claim 1, wherein the mass is a seismic mass of a spring-mass system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross section of a micromechanical sensor system according to one specific embodiment of the present invention.

(2) FIG. 2 shows a cross section of a micromechanical sensor system according to another specific embodiment of the present invention.

(3) FIG. 3 shows a top view onto a portion of a micromechanical sensor system according to one specific embodiment of the present invention.

(4) FIG. 4 shows a top view onto a portion of a micromechanical sensor system according to one specific embodiment of the present invention.

(5) FIG. 5 shows a view from below onto a thin layer of a micromechanical sensor system according to one specific embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) FIG. 1 shows in schematic form a cross section of a micromechanical sensor system according to one specific embodiment of the present invention.

(7) FIG. 1 shows in detail a cross section of a micromechanical sensor system 100. Micromechanical sensor system 100 includes a seismic mass 4 that is translationally movable or deflectable in z direction 7, i.e., upwardly or downwardly in FIG. 1. Situated on portions of bottom side 4′ of seismic mass 4, i.e., on one of the two sides of seismic mass 4 in the direction of a deflection in z direction 7, is a connecting layer 3 that is joined to a thin layer 2. A flexible area is situated between seismic mass 4 and thin layer 2. This area is formed by a recess 8 in connecting layer 3, between seismic mass 4 and thin layer 2. Two stops 5 and 6 are shown on the side of thin layer 2 facing away from seismic mass 4. Stop 5 has a greater thickness in z direction 7 than does second stop 6. In addition, stop 5 is farther outwardly situated, based on the midpoint of seismic mass 4 (situated in the area in the continuation of the seismic mass to the right in FIG. 1 (not shown here)), than stop 6. Seismic mass 4 as well as connecting layer 3 may be made of silicon. Seismic mass 4 and connecting layer 3 are mechanically fixedly anchored or connected to thin layer 2, which may likewise be made of silicon. The two stops 5 and 6 may be made of silicon, silicon nitride, or germanium.

(8) If movable micromechanical sensor system 100 is now deflected in negative z direction 7 due to mechanical overload, first stop 5 initially contacts an immovable silicon, silicon nitride, copper, or aluminum layer with a substrate bond 1. Upon further deflection, thin layer 2 yields to the movement and absorbs a portion of the kinetic energy of the overload. After a certain deflection of thin layer 2 in negative z direction 7, second stop 6, which in this case has greater rigidity than first stop 5, contacts immovable silicon layer 1, and movable mass 4 of micromechanical sensor system 100 comes to a rest.

(9) FIG. 2 shows in schematic form a cross section of a micromechanical sensor system according to another specific embodiment of the present invention.

(10) FIG. 2 essentially shows a micromechanical sensor system 100 according to FIG. 1. In contrast to micromechanical sensor system 100 according to FIG. 1, micromechanical sensor system 100 according to FIG. 2 now has stops 5, 5′ having the same design. In addition, micromechanical sensor system 100 is now designed as a z rocker; i.e., instead of a translational movement of seismic mass 4 according to FIG. 1, the seismic mass may now undergo a rotatory movement. The second stop having greater rigidity, denoted by reference numeral 6 in FIG. 1, may thus be dispensed with here. In FIG. 2, two stops 5, 5′ having the same design are provided which on the one hand have the same extension in the z direction, and on the other hand are also made of the same material or from the same layer.

(11) FIG. 3 shows in schematic form a top view onto a portion of a micromechanical sensor system according to one specific embodiment of the present invention.

(12) FIG. 3 shows in detail a top view onto a structured thin layer 2, made of silicon, of a micromechanical sensor system 100. Also indicated is a stop 5, in the middle of thin layer 2, that protrudes into the plane of the drawing in FIG. 3. Thin layer 2 is rectangularly bordered by a connection element 3. In addition, thin layer 2 in x direction 9 has a smaller extension than in y direction 9′. Furthermore, thin layer 2 in x direction 9 has three rows of rectangular recesses 10 that are used to adjust or set the overall rigidity of stop element 2, 5. Rectangular recesses 10 may be produced in a simple manner, while circular recesses in particular provide improved stress relief. The width of the recesses in y direction 9′ may be, for example, between 500 nm and 8 μm, in particular between 2 μm and 5 μm.

(13) FIG. 4 shows in schematic form a top view onto a portion of a micromechanical sensor system according to one specific embodiment of the present invention.

(14) FIG. 4 essentially shows a thin layer 2 and a connection element 3 according to FIG. 3. In contrast to connection element 3 according to FIG. 3, connection element 3 according to FIG. 4 is now situated only on narrow sides 11, 11′ of thin layer 2, and has a rectangular design. The rigidity of stop element 2, 5 may likewise be adjusted in this way. In another modification of connection element 3, not shown here, the connection element extends only in y direction 9′, at both the top and the bottom, across a portion of overall layer 2, resulting in a U-shaped connection element 3 to the left and right on narrow sides 11, 11′ of thin layer 2. The transitions of connection element 3 are advantageously rounded at the corners of the U shape, which reduces the stress in connection element 3.

(15) FIG. 5 shows in schematic form a view from below onto a thin layer of a micromechanical sensor system according to one specific embodiment of the present invention.

(16) FIG. 5 shows a thin layer 2 made of silicon in a view from below. Thin layer 2 has no structuring 10. Three stops 5, 5″ are also shown, stop 5 being situated essentially in the middle of thin layer 2 and being offset with respect to the two other stops 5″ in x direction 9. In y direction 9′, stop 5 is situated essentially in the middle of the two stops 5″.

(17) When thin layer 2 without structuring is now rotated along its bottom longitudinal side about y axis 9′, top stop 5 initially comes into contact with a substrate, and upon further overloading the two other stops 5″ then simultaneously come into contact with the substrate. Thus, stops 5, 5″ are, or form, a cascaded stop element 5, 5″. In other words, an elastic stop cascade is provided. This is made possible by the symmetrical arrangement of stops 5, 5″ in y direction 9′ and their asymmetrical arrangement along x direction 9.

(18) In another specific embodiment, one of the two stops 5″ may be removed, resulting in an overall asymmetrical arrangement of stops 5, 5″. In this way, a tilting motion may be exerted on a seismic mass 4 connected thereto, which as a whole further reduces sticking or adhesion of stops 5, 5″.

(19) The force ratio between stops 5, 5″ may be set via the particular angle of stops 5, 5″ relative to one another or relative to the deflection direction. The larger the angle that is selected, the greater the forces on the middle stop 5, and the lower the forces on the two lateral stops 5″ in x direction 9.

(20) To manufacture the micromechanical sensor system, the layers may be produced in succession in an additive process. Thus, for example, silicon may be initially deposited, structured, and then provided with a deposited and structured sacrificial layer, for example an oxide. Material is subsequently once again deposited, structured, and provided with an oxide layer. In a further step the oxide layers are removed from the spaces in between by gas phase etching, and the sensor system is thus exposed.

(21) In summary, the present invention has the advantage, among other things, that adhesion to stop structures as well as damage to the micromechanical sensor system may be avoided. In addition, a defined distribution of striking forces may be made possible. High rotational rigidity of the stop element in a sensor plane may likewise be provided. As the result of a flexible structuring of the thin layer, in particular in the form of a thin plate and clamping of same, i.e., the design of the connection element, the rigidity of the stop element perpendicular to a sensor plane may be adjusted as a function of the surface area and thickness of the thin layer, and in particular high rigidities may be achieved in this way.

(22) Although the present invention has been described with reference to preferred exemplary embodiments, it is not limited thereto, and is modifiable in numerous ways.