MICROMECHANICAL SYSTEM HAVING A STOP ELEMENT

Abstract

A micromechanical system includes a substrate; a functional element that is mounted to as to allow movement in relation to the substrate; and an elastic stop element. The stop element has a first end that is attached to the substrate, and a second end that is configured to engage with the functional element when the functional element is deflected by a predefined amount from a neutral position. The stop element has an elastic configure in a first direction that coincides with a preferred direction of the functional element, and in a second direction that extends at a right angle to the first direction.

Claims

1. A micromechanical system, comprising: a substrate; a functional element mounted so as to allow movement in relation to the substrate; an elastic stop element having a first end that is attached to the substrate, and a second end configured to engage with the functional element when the functional element is deflected by a predefined amount from a neutral position; wherein the elastic stop element is elastic in a first direction that coincides with a preferred direction of the functional element, and wherein the elastic stop element has an elastic configuration in a second direction that extends at a right angle to the first direction.

2. The system of claim 1, wherein the second end of the stop element has a concave configuration and a section of the functional element configured for the engagement has an elongated configuration.

3. The system of claim 1, wherein the second end of the stop element is elongated, and a section of the functional element configured for the engagement is concave.

4. The system of claim 2, wherein the elongated element has a convex end section.

5. The system of claim 4, wherein a radius of the convex element is smaller than a radius of the concave element.

6. The system of claim 1, wherein the stop element includes a first flexural member for producing the elastic deformability in the first direction, and a second flexural member, mounted on the first flexural member, for producing the elastic deformability in the second direction.

7. The system of claim 6, wherein two second flexural members are disposed parallel to each other and are connected to each other in their external regions.

8. The system of claim 1, wherein the preferred direction extends parallel to a surface of the substrate.

9. The system of claim 1, wherein the elastic element is elastic in a third direction that extends at a right angle to the two other directions.

10. The system of claim 9, wherein a contact structure of the type of a cup-and-saucer connection is configured between the functional element and the second end of the stop element.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0020] FIG. 1 shows a micromechanical system.

[0021] FIG. 2 shows a part of the micromechanical system from FIG. 1 in an enlarged view.

[0022] FIG. 3 shows a stop element on a micromechanical system.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a micromechanical system 100 having a substrate 105 and a functional element 110. For instance, micromechanical system 100 may include a sensor, in particular an acceleration sensor or a rate-of-rotation sensor. For easier referencing, a coordinate system having a first direction (X), a second direction (Y) and a third direction (Z), has been illustrated in FIG. 1 and the following figures in each case. Directions X and Y define a plane in which a surface of substrate 105 may extend. However, it should be noted that all other combinations and orientations of a Cartesian coordinate system are possible as specific embodiments. Micromechanical system 100 is normally able to be produced using means from the semiconductor technology and may include different semiconductor materials. Substrate 105 may serve as a solid assembly frame and may include silicon, for instance. Other elements of system 100 may include silicon dioxide or, as a conductive layer, a metallization.

[0024] Functional element 110 may be kept mobile with respect to substrate 105, for instance with the aid of an elastic suspension or an elastic diaphragm 115. In particular, functional element 110 is able to move along a preferred direction 120, which coincides with first direction X. However, mobility in a transverse direction 125, which extends at a right angle to preferred direction 120, is not always able to be prevented completely. In the specific embodiment illustrated, transverse direction 125 coincides with second direction Y.

[0025] If no further forces are acting on functional element 110, then it assumes a predefined neutral position. Exposed to external influences, functional element 110 may move from the neutral position by a predefined amount. In order to limit such a movement, at least one stop element 130 is provided, which includes a first end 135 and second end 140. First end 135 is attached to substrate 105, and second end 140 is configured to engage with functional element 110 when functional element 110 is deflected from the neutral position by a predefined amount. In the illustrated specific embodiment, functional element 110 is deflected in such a way that an engagement 145 is present at two of the four stop elements 130 illustrated.

[0026] Between first end 135 and second end 140, stop element 130 includes a flexural member 150 which permits a movement of second end 140 relative to first end 135 at least along first direction 120.

[0027] FIG. 2 shows a region of an engagement 145 between functional element 110 and stop element 130 of micromechanical system 100 of FIG. 1. The illustrated part essentially corresponds to stop element 130 shown in the upper left area in FIG. 1.

[0028] Functional element 110 encompasses a section 205, which is configured for an engagement with second end 140 of stop element 130. Surfaces of section 205 of functional element 110 and of second end 140 of stop element 130 are illustrated with a greater roughness. When functional element 110 executes a combined movement 210, which is composed of movements in first direction 120 and second direction 125, then a lateral, chafing or scuffing movement may result between section 205 and second end 140. Especially in cases where a force component along first direction 120 is low, various surface structures in an atomic or molecular scale may successively make contact with one another between section 205 and second end 140 during the sliding process. This contact may take place in such a way that continuously increasing sticking is produced because increasingly more and increasingly better adhering surface segments make contact with one another in the lateral movement. It is statistically improbable that a very sticky or meshed surface condition shifts to a less sticky condition during the described process, especially because the kinetic energy of functional element 110 diminishes during the lateral movement.

[0029] As a consequence, stop element 130 may cause a critical, adhesion-producing effect due to the sliding movement along second direction 125, and the desired force-reaction of stop element 130 in opposition to the sticking may be very heavily reduced. This may particularly stem from the fact that the detachment force is acting in a perpendicular direction with respect to the adhering surface segments. In the type of stop or movement described, elastic stop element 130 may largely have no effect.

[0030] The risk of sticking in a lateral movement along second direction 125 may be considerable in particular when one of the surfaces of section 205 or of second end 140 of stop element 130 is rough not only in the atomic range but also includes larger structures such as grooves, blades or roughness in the sub-micrometer to micrometer range. This characteristic is frequently encountered in MEMS and nano-structures.

[0031] FIG. 3 shows a specific embodiment of a stop element 130 in a micromechanical system 100 like the one shown in FIG. 1. Stop element 130 is configured to exhibit an elastic behavior both along first direction 120 and along second direction 125. Toward this end, flexural member 150 may be configured in such a way that it is elastic along both directions 120, 125. In the specific embodiment shown here, a first flexural member 150.1 and a second flexural member 150.2 are provided in cascading form. Second flexural member 150.2 is fixed in place on first flexural member 150.1 so that both flexural members 150.1, 150.2 lie mechanically in series between first end 135 and second end 140. One of flexural members 150.1, 150.2 may also be provided with a frame structure, as shown in FIG. 3 by way of example, with respect to second flexural member 150.2. For this purpose, two second flexural members 150.2 are disposed in parallel with each other, their external regions being connected to each other, which may be with the aid of a frame element 305. Frame element 305 may be elastically deformable in a plurality of dimensions. The introduction or dissipation of forces preferably takes place in the interior region of second flexural member 150.2.

[0032] Furthermore, it may be provided that a contact structure 310 is configured between functional element 110 and stop element 130 for the engagement. This is done in that second end 140 of stop element 130 and section 205 of functional element 110 configured for an engagement with second end 140 are given a mutually corresponding configuration. For one, this allows for free mobility of functional element 110 with respect to substrate 105 along both directions 120, 125 as long as the deflection of functional element 110 from the neutral position does not exceed a predefined amount. For another, it allows for the realization of a reliable frictional connection along both directions 120, 125 when the predefined amount is exceeded. Toward this end, it may be provided that second end 140 is configured in concave form and section 205 is configured in elongated form, i.e. is oblong, in particular. A reversed specific embodiment, in which second end 140 is elongated and section 205 is concave, is possible as well.

[0033] In the specific development illustrated, second end 140 is configured in a C-shape or a U-shape in the plane of directions 120, 125, in particular. If a free distance between section 205 and second end 140 along the two directions 120, 125 is to differ, then the concave form of second end 140 is able to be modified accordingly. In other words, the U-shape may have a correspondingly flatter or narrower development.

[0034] In addition, it may be provided that section 205 includes a convex end section 315. A radius of curvature of end section 315 may be smaller than a radius of curvature of concave second end 140.

[0035] In another specific embodiment, stop element 130 may additionally have an elastic configuration along third direction (Z). For this purpose, for instance, first flexural member 150.1 may be elastic also along the third direction, or a dedicated third flexural member may be provided which is connected in series with the other two and ensures the elasticity in the Z-direction. Contact structure 310 may easily be expanded to the third direction in that the surfaces, provided for the mutual engagement, of second end 140 of stop element 130 and of section 205 of functional element 110 are provided essentially in axial symmetry with respect to second direction 125. Concave second end 140 is then concave also in the third dimension, in the manner of a dish or bowl. Convex end section 315 of section 205 may be configured in a three-dimensionally convex form, in the form of a spherical segment.