DE19813941A1 - Micromechanical acceleration sensor - Google Patents

Abstract

The acceleration sensor includes an end stop (13) on a substrate, against which a seismic mass (2) lies in a rest position under the biasing force of a flexion spring (5). A voltage source and an electrical wire (25) are provided for exerting an electrostatic force on the seismic mass.

Description

The invention relates to a micromechanical acceleration sensor with a seismic mass, at least one spring element for the resilient mounting of the seismic mass, detection means for detecting movement of the seismi mass from a rest position to a switch position, a substrate on which the spring element and the detection means are arranged.

Such a micromechanical device is known from patent specification DE 42 29 068 C2 Accelerometer known in which the seismic mass at acceler conditions that are smaller than a predetermined first threshold value, only slightly is deflected from the rest position when the first threshold value is exceeded jumps to the switch position and then falls below a second Threshold value, which is smaller than the first threshold value, from the switch position in the rest position returns. The dependence between that on the seismic Mass acting acceleration and the resulting deflection is nonlinear in this known sensor and is formed by the shape of the Spring elements reached; the deflection of the seismic mass is for small ones  Acceleration values relatively small and overpro for large acceleration values portionally large. The path that the seismic masses take from their rest position to the Must switch position before the detection means reaching the Signal switching position must therefore be greater than the deflections of the seismic mass due to accelerations below the given acceleration threshold.

Each seismic mass forms a mass-spring system with the resilient bearing with a design-related resonance frequency. Now the frequency drops changing acceleration caused, for example, by a vibration can be approximately with the resonance frequency of the micromechanical Accelerator switch together, then also for small accelerations relatively large deflections of the seismic mass. This can cause the seismic mass to reach the switch position, although the one acting acceleration is below the predetermined threshold. The can be remedied within certain limits by the fact that the path between Rest and switch position is further increased in construction. This makes everything dings also increases the response time between the exceeding of the predetermined threshold value and the switch position is reached. Of the micromechanical acceleration sensor consequently reacts with deceleration, ie with an undesirably high response time.

The object of the present invention is the micromechanical acceleration tion sensor of the type mentioned in such a way that the seismic Mass with exceeding a predetermined acceleration threshold value recognizes high detection reliability, the response time being as short as possible.

The task becomes the beginning with the micromechanical acceleration sensor mentioned type according to the invention solved in that a stop on the substrate is provided on which the seismic mass in its rest position against spring voltage is present.

The advantages of the invention are in particular that the micromechanical Accelerometer is insensitive to accelerations that are under are half of the predetermined first acceleration threshold value. This Insensitivity prevents the seismic mass from rocking when changing accelerations below the first acceleration threshold value. Undesired resonance effects and consequent incorrect detection of the  this effectively prevents acceleration that is actually effective. There the seismic mass only when the first acceleration threshold is exceeded value is deflected, the path between the rest position and the switching position and thus the response time of the micromechanical accelerator be reduced. Because of the short response time at the same time high probability of correct detection can be the micro according to the invention Use mechanical acceleration sensors particularly advantageously where they are Properties are mandatory. This is in the area of occupant protection systems for motor vehicles, such as in an airbag or a Belt tensioners, or for security systems, e.g. B. as the glass break sensor.

In a preferred embodiment, means are provided for the spring chip overlay an electrostatic force. The electrostatic force can one is used to determine the first acceleration threshold, which is used for Deflection of the seismic mass from the rest position is required to change. In the event that the electrostatic force acts in the direction of detection, the acceleration threshold decreases. Will the electrostatic force applied against the direction of detection, then the first changes Acceleration threshold to higher values. On the other hand, it can electrostatic force must be so great that the seismic mass against the back positioning force of the spring elements deflected from the rest position into the switching position becomes. This enables the functionality of the micromechanical acceleration to check the sensor by means of a self-test. It can be broken out of the electrostatic force determines the level of the acceleration threshold that must be reached to keep the seismic mass from resting to shift the switch position.

In a further advantageous embodiment of the micro according to the invention mechanical acceleration sensor is the seismic mass at several Suspended spring elements. This makes the seismic mass more directionally stable held and thus less sensitive to accelerations in directions, that of the detection direction of the micromechanical acceleration sensor differ.

The spring elements of the micromechanical acceleration are particularly preferred tion sensor designed as thin spiral springs, which are characterized by their simple Characterize structure and the good predictability of the spring behavior. this applies in particular also for the production of the micromechanical acceleration sensors as semiconductor microstructure. The spring properties can, for example  when specifying the material, still be optimized by using the cross section Length or the course of the spiral springs can be adapted to the needs.

The spiral springs are preferably each with one end on the substrate and with their other end attached to the seismic mass; the attachment points the substrate and the attachment points on the seismic mass are suitable selected, for example, they lie at the corners of a rectangle, but can also be placed in other suitable places.

The detection means of the micromechanical acceleration sensor include preferably a contact section on the seismic mass and at least one contact stop arranged on the substrate. Exceeds the acceleration the first acceleration threshold, then the seismic mass moves from the rest position against the switch position. Exceeds the acceleration the second threshold, the seismic mass reaches the so-called switching position in which the contact portion of the mass with the contact stop of the Comes into contact with the substrate. The contact section and the contact stop are electrically conductive. Through electrical lines that lead to contact section or lead to the contact elements, an evaluation circuit Detect contact between the contact section and the contact stop. Alternatively, it is possible that the contact section with appropriate deflection the seismic mass connects two contact stops in an electrically conductive manner. In a another alternative embodiment, two contact stops are such arranged to each other that the seismic mass with appropriate deflection one of the contact stops in this way relative to the other contact stop moves that both contact stops touch and an electrically conductive Form a connection.

The contact stop can be designed to be stationary on the substrate, preferably however, the contact stop springs in the direction of movement of the seismic mass and is designed as a contact spring which is attached at one end to the substrate, and which forms the counter contact at its other, free end against which the Contact section of the seismic mass starts up. By this constructive measure The contact stop cushions the seismic mass in its movement out of the Rest in the switch position and at the same time prevents an undesirable Contact bounces. If an evaluation circuit continues to be used, a pre given hold time for the detected signal, the probability that a triggering event is reliably detected is significantly increased.  

In a preferred embodiment of the micromechanical acceleration sensors are several contact stops in the detection direction of the seismic Mass staggered on the substrate so that the seismic Mask with a movement in the direction of detection first with, and with Next move comes into contact with another contact stop. Hereby can, for example, with a seismic mass two different Be acceleration threshold values are detected.

The seismic mass of the micromechanical Be particularly preferably acceleration sensor one by several fingers and corresponding intermediate clean, flat comb structure that is a short distance above one flat substrate surface is suspended from the spring elements. In the twos Spaces that are fixed to the substrate are preferred on the substrate arranged parallel to the fingers of the comb structure. In addition to the properties of Spring elements, the mechanically or electrostatically generated bias of the seismic mass and its physical mass, also affects the damping the behavior of the micromechanical acceleration of the mass-spring system sensor. The damping is essentially due to the air resistance that the seismic mass experiences during its movement and is therefore in the essentially of a shape of the seismic mass and its distance depending on the substrate. Through the comb structure in connection with the substrate The air damping of the mass-spring system can be built into solid wall elements interpret wide limits according to requirements.

The wall sections are at a sufficient distance from the fingers, so that the seismic mass moves freely in its entire range of deflection without hitting your fingers.

The micromechanical acceleration sensor particularly preferably forms the Fingers of the comb structure and the interlocking, complete wall sections tare electrodes. A first potential is applied to the fingers and to the Wall sections a second potential, so the fingers and the wall sections of the comb structure as detection means for capacitive measurement of a Use movement or acceleration of the seismic mass. The one for this required potential difference is very small for these measurement purposes. In contrast, the If the potential difference is chosen to be larger, it is formed by the applied voltage noticeable electric fields and between the fingers and the wall sections forces with which the seismic mass is then added to that of the  Forces applied spring elements is applied.

In an expedient development of the micromechanical acceleration sensors become those between a finger and the neighboring wall cut existing capacities measured independently of each other. The size The capacities depend on the position of the corresponding finger the neighboring wall sections. When the finger moves relative to the wall sections increases the capacity between the finger and one Wall section, while the capacity between the finger and the other Wall section reduced at the same time. A measurement error can be reduced if Both measurement results are linked by suitable mathematical operations become. In a simple case, the two measured capacitance values a difference is made to be equivalent to both capacitance measurements To be able to suppress disturbances as far as possible.

The position of the finger between the wall sections and thus the position of the seismic mass can thus be measured using the differential principle. This enables a more accurate measurement of an analog acceleration signal - especially as a function of time. From the analogue acceleration supply signal or from its temporal course, for example Recognize the dangerous situation before the acceleration threshold is reached. In addition, e.g. B. can be concluded on the severity of the accident.

In one embodiment of the invention, the seismic mass contains a rest approach that preferably resiliently protrudes from the seismic mass and at a Deflection from the original position to the rest position engages behind the stop and prevents a return to the original position.

The micromechanical acceleration sensor is preferably used with relaxed Spring elements made. In a manufacturing step, the seismic Mass moved from the original position to the rest position. The seismic mass deflected against the building force of the spring elements. When the seismic mass reaches the rest position, the catch starts behind the Stop against which the seismic mass then rests under spring preload. The seismic mass is determined, for example, by a predetermined acceleration, or by an electrostatic force from the original position to the rest position deflected.  

In an alternative embodiment, the locking approach of the seismic mass be rigid, while the stop springs transversely to the detection direction. In this embodiment, the seismic mass moves from the origin in the rest position, presses the resilient stop with the catch transverse to the direction of detection from its relaxed position. Reaches the seismic If the rest position is measured, the stop springs back behind a stop or into a recess of the seismic mass and prevents the seismic Mass runs back to the original position.

The micromechanical acceleration sensor is particularly preferred in one Technology for the production of microstructures, in particular based on Silicon, realized. The galvanic additive technology is suitable for this reversible, the integration of metallic microstructures on preprocessed Wafers and thus the arrangement of the micromechanical acceleration sensor allowed on any ASIC. The bulk-micro also proves to be suitable machining technology in which the micromechanical acceleration sensor is etched from a monocrystalline silicon by trench etching processes. In this Technology allows conductor tracks to be used, for example, through implantation Coating with metallic materials or by galvanic coating apply. Alternatively, surface micro machining technology is also available the sensor-specific electronics with the micromechanical Accelerometer can be integrated.

The micromechanical acceleration sensor described above has one design-related detection direction. Should be directed differently accelerations can be detected, several differently oriented Micromechanical acceleration sensors combined in one unit become. For example, two micromechanical acceleration sensors with oppositely aligned detection directions in one unit summarized, so positive and negative accelerations in one direction can be detected. Furthermore, micromechanical accelerations can also combined with different acceleration threshold values become. This can be used, for example, to accelerate over time record values.

Advantageous developments of the invention are due to the features of the sub claims marked. In the following the invention with reference to the drawing gene exemplified. Show it:

Figure 1 is a plan view of a first embodiment of a micromechanical acceleration sensor in its rest position.

FIG. 2 shows a side view of the micromechanical acceleration sensor according to FIG. 1;

Figure 3 is a plan view of the first embodiment of a micromechanical acceleration sensor in its original position.

FIG. 4 shows a side view of the micromechanical acceleration sensor according to FIG. 3;

Figure 5 is a plan view of a second embodiment of a mikrome chanical acceleration sensor in its rest position.

FIG. 6 shows a side view of the micromechanical acceleration sensor according to FIG. 9;

Figure 7 is a plan view of the second embodiment of a micromechanical acceleration sensor in its original position.

FIG. 8 shows a side view of the micromechanical acceleration sensor according to FIG. 11;

Figure 9 is a schematic representation of an arrangement of two mikrome chanical acceleration sensors.

Figure 10 is a schematic illustration of an arrangement of four micro-mechanical acceleration sensors.

11 is a plan view of a third embodiment of a micromechanical acceleration sensor's in its rest position.

12 is a plan view of a fourth embodiment of a micromechanical acceleration sensor's in its rest position.

13 is a plan view of a fifth embodiment of a micromechanical acceleration sensor's in its rest position.

Fig. 14 is a plan view of a sixth embodiment of a micromechanical acceleration sensor in its rest position;

Figure 15 is a plan view of a seventh embodiment of a micromechanical acceleration sensor's in its rest position.

Fig. 16 is a plan view of an eighth embodiment of a micromechanical acceleration sensor in its rest position.

Fig. 17 is a plan view of a ninth embodiment of a micromechanical acceleration sensor in its original position.

Fig. 18 is a plan view of a ninth embodiment of a micromechanical acceleration sensor in its rest position.

Figs. 1 and 2 show a first embodiment of a micromechanical acceleration sensor 1. A seismic mass 2 , which has an essentially flat, plate-shaped structure, is arranged at a predetermined distance above a substrate 11 . Four bending elements 5 resiliently support the seismic mass 2 . Detection means 7 and 9 serve to detect a movement of the seismic mass 2 from a rest position into a switch position. In the Figure 1 depicting the lungs. 2 and is the seismic mass 2 in the rest position.

The seismic mass 2 has an elongated, rectangular central section 3 , on the longitudinal sides of which laterally projecting fingers 19 and at the front end of the central section 3 in the longitudinal direction an elongated contact section 7 with laterally projecting, at an acute angle to the longitudinal direction, resilient latching approaches 26 are arranged. The longitudinal direction of the central section 3 and the contact section 7 runs parallel to a design-related detection direction 15 , in which the seismic mass 2 is deflected when acceleration occurs. The lateral fingers 19 formed integrally on the central section 3 of the seismic mass 2 define recesses 17 and form a double comb structure 21 .

Wall sections 23 sit in the recesses 17 on the substrate 11 parallel and spaced apart from the fingers 19 . The recesses 17 are dimensioned so large that the seismic mass 2 can move freely in its entire deflection area without hitting the wall sections 23 with the fingers 19 . The fingers 19 and wall portions 23 are made of an electrically conductive material, e.g. B. from silicon predetermined doping, from a coating with metallic materials or a galvanic coating, and form complementary electrodes, between which a voltage can be applied. For this purpose, electrical lines 25 on the one hand connect the fingers 19 and on the other hand the wall sections 23 to one pole of a voltage source 24 .

In the area of the corner edges of the central section 3 , four spiral springs 5 are each fastened to the seismic mass 2 , the other end of the spiral springs 5 is fastened to a holding block 6 in each case. The holding blocks 6 are arranged on the surface of the substrate 11 at the corners of a rectangle which conforms to the central section 3 and in the example shown includes the fingers 19 . The storage of the seismic mass 2 by means of the bending springs 5 restricts the freedom of movement of the seismic mass 2 essentially to a movement along the detection direction 15 parallel to the substrate.

Two resilient contact stops 9 , which together with the contact section 7 form the detection means, run essentially perpendicular to the detection direction 15 above the substrate 11 . With one end, the contact stops are attached to substrate-fixed holding blocks 6 a. The free end of the contact stops 9 is in the detection direction 15 a predetermined distance before the contact section 7 .

On both sides of the elongated contact section 7 , a stop 13 is firmly connected to the substrate 11 adjacent to the free ends of the latching projections 26 . The locking lugs 26 are in the so-called rest position of the seismic mass 2 in front of the stops 13 and thereby tension the spiral springs 5 , so that the locking lugs 26 abut against the stops 13 under the pretension of the spiral springs 5 .

FIGS. 3 and 4 show the acceleration sensor 1 in its original position in which the spiral springs 5 are released and the locking lugs 26 do not lie in front of the stops 13. In order to bring the seismic mass 2 from the original position into the rest position, a force in the detection direction 15 must act on the seismic mass 2 . This force can be applied, for example, by an acceleration acting on the seismic mass 2 or by temporary application of an electrostatic field between the fingers 19 and the wall sections 23 .

In Figs. 5 to 8 show a second embodiment of the micromechanical Be is shown schleunigungssensors 1, wherein the seismic mass is suspended from only egg ner spiral spring 5 2; FIGS. 5 and 6 show the position of rest, Fig. 7 and 8, the origin position. In this embodiment, the seismic mass 2 also comprises an elongated, parallelepiped-shaped central section 3 which runs in the longitudinal direction parallel to the detection direction 15 and has a latching projection 26 on the contact section 7 . Spaced fingers 19 form a comb structure 21 and are formed only on one long side of the central section 3 , which is opposite the spiral spring 5 . In the direction of detection 15 , the elongated contact section 7 adjoins the front end face of the central section 3 in the longitudinal direction, which has a smaller width than the central section 3 , but can also be made wider. From the free end of the contact section 7 extends laterally a finger-shaped latching projection 26 , which is set against the detection direction 15 by a predetermined angle. A stop 13 sits sideways from the contact section 7 , adjacent to the free end of the latching shoulder 26, firmly on the substrate 11 , the latching shoulder 26 resting against the stop 13 in the rest position of the seismic mass 2 under pretension of the spiral spring.

The spiral spring 5 engages - opposite the comb structure 21 - approximately centrally on the long side of the central section 3 and supports the seismic mass 2 at a distance from the substrate 11 , compare FIGS . 6 and 8. With its other end, the spiral spring 5 sits above the substrate 11 extends substantially perpendicular to the detection direction 15 , on a substrate-fixed holding block 6 . In the recesses 17 , wall sections 23 are parallel and spaced apart from the fingers 23 on the substrate 11th The recesses 17 are in turn dimensioned so large that the seismic mass 2 can move freely in its entire deflection area without hitting the wall sections 23 with the fingers 19 . The fingers 19 and wall sections 23 are electrically conductive and form complementary electrodes.

Fig. 9 schematically shows a possible arrangement of two micromechanical acceleration sensors 1 , in which two acceleration sensors 1 with oppositely directed detection direction 15 are arranged adjacent to one another on a substrate. This makes it possible to detect positive and negative accelerations in one direction.

In Fig. 10, a possible arrangement of four micromechanical acceleration sensors 1 is shown schematically. In this arrangement, two micromechanical acceleration sensors 1 with their detection directions 15 are aligned opposite each other in pairs, the two pairs lie in one plane and are rotated by 90 ° with respect to one another. Accelerations in the four detection directions 15 can thereby be detected.

In Figs. 11 to 15, various embodiments of the latching shoulders 26 and the contact stops 9 are shown. The seismic mass 2 is only shown schematically in FIGS. 11 to 15, the remaining parts of the acceleration sensor are omitted for the sake of clarity.

In Fig. 11, in a third embodiment of the micromechanical acceleration sensor on the front contact section 7, two lateral latching projections 26 are present, which engage a correspondingly positioned stop 13 in the rest position. In front of the contact section 7 there is only a resilient contact stop 9 , which is connected to a corresponding, substrate-fixed holding block 6 a.

FIG. 12 shows the front contact section 7 of a fourth embodiment of the acceleration sensor with only one latching projection 26 , which in the rest position engages behind a corresponding stop 13 arranged on the side of the contact section 7 . Before the contact section 7 is a resilient contact stop 9 , which is connected to a corresponding substrate-fixed holding block 6 a.

In the fifth embodiment shown in FIG. 13, the front contact section 7 has a latching projection 26 which engages behind a corresponding stop 13 in the rest position. In this embodiment, the stop 13 is designed to be resilient essentially transversely to the detection direction 15 . The locking projection 26 can sit rigidly on the seismic mass 2 . In front of the contact section 7 there is a resilient contact stop 9 which is connected to a corresponding holding block 6 a fixed to the substrate.

Fig. 14 shows a sixth embodiment of the micromechanical sensor Accelerati supply having a first and a second contact stop 9, which are designed as bending springs. Holding blocks 6 a store the contact stops 9 substantially perpendicular to the detection direction 15 and spaced apart from the substrate, so that the free ends of the contact stops 9 spring 15 essentially in the detection direction. On the front contact section 7 there are two lateral latching projections 26 which engage a correspondingly positioned stop 13 in the rest position. The free end of the first contact stop 9 is at a predetermined first distance and the free end of the second contact stop 9 is at a predetermined second distance from the stops 13 , the predetermined first distance being smaller than the predetermined second distance. If an acceleration acting on the seismic mass exceeds a first threshold value, then the seismic mass 2 moves from the rest position in the detection direction 15 . If the acceleration reaches a second threshold value, the contact section 7 of the seismic mass 2 meets the first contact stop 9 , which uses the smaller distance from the stop 13 . If the acceleration acting on the seismic mass 2 is greater than a predetermined third threshold value, the seismic mass 2 bends the first contact stop 9 in the detection direction 15 until the contact section 7 also touches the second contact stop 9 , which is the greatest distance from the stop 13 Has.

In the seventh embodiment of the micromechanical acceleration sensor shown in FIG. 15, two holding blocks 6 a are arranged on the substrate. The holding blocks 6 a each store a contact stop 9 , which is formed as a spiral spring, essentially perpendicular to the detection direction 15 and spaced from the substrate, so that the free ends of the contact stops 9 spring substantially in the detection direction 15 . When viewed in the detection direction 15 , the free ends of the two contact stops 9 overlap in sections. In the rest position of the seismic mass 2 , the contact stops have a predetermined distance from one another. If an acceleration acting on the seismic mass 2 exceeds a first threshold value, then the seismic mass 2 moves from the rest position in the detection direction 15 . If the acceleration reaches a second threshold value, the contact section 7 of the seismic mass 2 meets the adjacent contact stop 9 , which is arranged in the detection direction 15 in front of the other contact stop. If the acceleration acting on the seismic mass 2 is greater than a predetermined third threshold value, then the seismic mass 2 bends one contact stop 9 in the detection direction 15 until it contacts the other contact stop 9 . In the case of electrically conductive contact stops 9 , the reaching of the third acceleration threshold value can be detected by a contact closure between the two contact stops 9 .

Fig. 16 shows an eighth embodiment of the micromechanical Accelerati supply sensor with two in the detection direction 15 of staggered, fixed contact substrate stops 9. The side of the front contact section 7 is arranged flexible locking lugs 26 , which engage in the rest position corresponding to strokes 13 are electrically conductive in the illustrated embodiment and take over the function of the contact section 7th Electrical contact between the contact stops 9 and the contact section 7 takes place via the conductive latching projections 26 . As a result of the offset arrangement of the contact stops 9 , different acceleration threshold values can be detected, as in the sixth embodiment of the micro-mechanical acceleration sensor.

In Figs. 17 and 18 a ninth embodiment of the micromechanical Be is schleunigungssensors shown in the origin position and in the rest position. FIGS. 17 and 18 are limited to a representation of the central portion 3 of the seismic mass 2, the fingers 19 and the wall portions 23 a and 23 b. The remaining parts of the acceleration sensor have been omitted for the sake of clarity. In contrast to the embodiments described above, in the ninth embodiment the wall sections arranged between the fingers 19 are double-walled. The fingers 19 and the wall sections 23 a and 23 b are electrically conductive and form electrodes between which a voltage can be applied. The fingers 19 form with the respective adjacent wall sections 23 a and 23 b each have two capacities which can be measured independently of one another. The capacities change depending on the position of the finger 19 relative to the adjacent wall sections 23 a and 23 b. The measurement accuracy can be increased by a suitable mathematical combination of the two capacitances formed by one of the fingers 19 with the respective wall sections 23 a and 23 b. As a result, it is more precisely possible to determine the position of the finger 19 or, when the capacitance changes over time, a movement of the finger 19 relative to the adjacent wall sections 23 a and 23 b.

Reference list

1

Micromechanical acceleration sensor

2nd

Seismic mass

3rd

Central section

5

Spring element

6

,

6

a holding block

7

Contact section

9

Contact stop

11

Substrate

13

attack

14

Front section of the stop

15

Direction of movement

17th

Recess

19th

finger

21

Comb structure

23

Wall section

23

a, b wall sections

24th

Voltage source

25th

Electrical line

26

Resting approach

Claims (16)

1. Micromechanical acceleration sensor ( 1 ) with
a seismic mass ( 2 ),
at least one spring element ( 5 ) for the resilient mounting of the seismic mass ( 2 ),
Detection means ( 7 , 9 ) for detecting a movement of the seismic mass ( 2 ) from a rest position into a switching position,
a substrate ( 11 ) on which the spring element ( 5 ), the seismic mass ( 2 ) and
the detection means ( 7 , 9 ) are arranged,
marked by
a stop ( 13 ) on the substrate ( 11 ) against which the seismic mass ( 2 ) rests under spring tension in its rest position. 2. Micromechanical acceleration sensor according to claim 1, characterized by means ( 24 , 25 ) for applying an electrostatic force to the seismic mass ( 2 ). 3. Micromechanical acceleration sensor according to one of the preceding claims, characterized in that the spring elements ( 5 ) are designed as spiral springs. 4. A micromechanical acceleration sensor according to any one of the preceding claims, characterized in that the detection means (7, 9) comprise at least a contact portion (7) on the seismic mass (2) and on said substrate (11) to higher-level contact stop (9). 5. Micromechanical acceleration sensor according to claim 4, characterized in that the contact stop ( 9 ) is formed substrate-tight. 6. Micromechanical acceleration sensor according to claim 4, characterized in that the contact stop ( 9 ) in the direction of movement ( 15 ) of the seismic mass ( 2 ) is resilient. 7. Micromechanical acceleration sensor according to claim 6, characterized in that a plurality of contact stops in the direction of movement ( 15 ) of the seismic mass ( 2 ) are arranged offset from one another on the substrate ( 11 ). 8. Micromechanical acceleration sensor according to one of the preceding claims, characterized in that the seismic mass ( 2 ) has a plurality of spaced fingers ( 19 ) and that in the recesses ( 17 ) between the fingers ( 19 ) substrate-fixed wall sections ( 23 ) are arranged. 9. Micromechanical acceleration sensor according to claim 8, characterized in that the wall sections ( 23 ) in the rest position of the seismic mass ( 2 ) and when moving into the switch position have at least a predetermined, minimum distance to the fingers ( 19 ). 10. Micromechanical acceleration sensor according to claim 8 or 9, characterized in that the fingers ( 19 ) and the wall sections ( 23 ) form interlocking, complementary electrodes. 11. A micromechanical acceleration sensor according to claim 10, characterized in that the sections between the fingers ( 19 ) arranged Wandab ( 23 ) are each double-walled ( 23 a, 23 b) and each form two separate electrodes. 12. Micromechanical acceleration sensor according to claim 10 or 11, characterized in that the detection means ( 7 , 9 ; 19 , 23 ), the fingers ( 19 ) and the wall sections ( 23 ) for capacitive measurement of a movement or acceleration of the seismic mass ( 2 ) include. 13. Micromechanical acceleration sensor according to one of the preceding claims, characterized in that the means for applying a voltage source ( 24 ) and electrical lines ( 25 ) for applying a voltage between the seismic mass ( 2 ) and the substrate-fixed wall sections ( 23 ) . 14. Micromechanical acceleration sensor according to one of the preceding claims, characterized by a locking projection ( 26 ) on the seismic mass ( 2 ) which engages the stop ( 13 ) when the seismic mass ( 2 ) is deflected from a relaxed original position into the prestressed rest position prevents a return to the original position. 15. Micromechanical acceleration sensor according to one of the preceding claims, characterized in that the seismic mass ( 2 ) is formed in a substantially plattenför shape and was by the spring elements ( 5 ) in a predetermined Ab above in a deflection range of the seismic mass ( 2 ) in essential flat substrate ( 11 ) is held. 16. Micromechanical acceleration sensor according to one of the preceding Expectations, characterized in that the micromechanical acceleration switch in a technology for the production of microstructures, in particular based on Silicon.