EP3180287A1

EP3180287A1 - Microelectromechanical device sensitive to mechanical forces applied off-plane

Info

Publication number: EP3180287A1
Application number: EP15767206.4A
Authority: EP
Inventors: François-Xavier BOILLOT
Original assignee: Tronics Microsystems SA
Current assignee: Tronics Microsystems SA
Priority date: 2014-08-13
Filing date: 2015-08-07
Publication date: 2017-06-21
Also published as: WO2016024064A1; FR3024872A1

Abstract

Microelectromechanical device made from a semiconductor substrate and comprising at least a main mass (1) able to move rotationally about an axis of rotation (4) parallel to the plane of the substrate under the effect of a first mechanical force applied. The device further comprises at least one mechanical detection assembly formed by: - an intermediate mass (51, 52) connected to an anchor zone (2) via mechanical connection means (61, 62) allowing the intermediate mass (51, 52) a movement parallel to the plane of the substrate under the effect of a second mechanical force applied inducing a movement of the device along an axis X parallel to the plane of the substrate and perpendicular to the axis of rotation (4); and - of a strain gauge (71, 72) secured to the main mass (1) via a first attachment point (711, 721) and secured to the intermediate mass (51, 52) via a second attachment point (712, 722), the movements of the first attachment point (711, 721) and of the second attachment point (712, 722) being in substantially identical directions with different amplitudes under the effect of the first force applied, and in substantially identical directions with substantially equal amplitudes under the effect of the second force applied.

Description

MICROELECTROMECHANICAL DEVICE HAVING SENSITIVITY TO OUTSTANDING MECHANICAL SOLICITATION

FIELD OF THE INVENTION

The present invention relates to microelectromechanical systems, also referred to in English by the acronym MEMS for "Micro-ElectroMechanical Systems". In particular, the present invention relates to a transducer MEMS detection said "off plan". The invention is particularly suitable for the realization of magnetometer or accelerometer.

PRIOR STATE OF THE TECHNIQUE

Micro-electromechanical force transducers, such as accelerometers, gyrometers or magnetometers, are typically in the form of devices comprising a moving mass and detection means measuring the displacements of this mobile mass under the effect of a force applied to it. Such a force may in particular be induced by an acceleration of the object on which the transducer is carried or by a magnetic field applied to the object.

In practice, the moving mass is made from a semiconductor substrate and is generally in the form of a layer of thickness of the order of one or more tens of microns, parallel to the plane of the substrate . Deformable elements coupling the moving mass to fixed anchoring zones maintain the mobile mass in suspension while allowing its displacement under the effect of the force to be measured. In addition, the mobile mass is coupled to means for detecting its displacements consecutive to the application of the force to be measured. In particular, in the case of a so-called "out-of-plane" detection transducer, the architecture is such that these detecting means provide a signal proportional to the out-of-plane force to be measured, and a much smaller amplitude signal under the effect of a force in the plane of the substrate. In the case, for example, of transducers using strain gauges, it is advantageous for off-plane displacements of the moving mass to generate maximum stresses on each of the gauges and, conversely, parasitic displacements in the plane of the mass. mobile device exert on each of the gauges minimal parasitic stresses, which can not be may, however, be neglected during measurements.

In practice, it is therefore advantageous to overcome these measurement noises resulting from the parasitic stresses exerted on these gauges, making the transducer detection system the least sensitive to unwanted mechanical stresses, such as accelerations or shocks, generating parasitic displacements of the moving mass parallel to the plane of the substrate.

Thus, in order to reduce the sensitivity of the detection system to these parasitic displacements in the plane, it is common, particularly in the case of accelerometers, to integrate means for decoupling the mobile mass, in the form of, for example, link arms or springs, to limit any unwanted movement of the moving mass. An example of such decoupling means is described in WO 2014/102507. However, the addition of these decoupling means may have the disadvantage of increasing the overall size of the transducer, as well as reducing its sensitivity.

SUMMARY OF THE INVENTION

In this context, an objective of the present invention is to propose a solution for the production of a transducer with detection or displacement outside the reduced space plane, in which the mechanical stresses called "in the plane" of the moving mass are not not detected. The proposed solution consists in making the variations of the detection means induced by parasitic displacements of the transducer virtually nil.

The present invention thus relates to a microelectromechanical device made in a semiconductor substrate whose layers are parallel to a plane of the substrate. The device comprises in particular:

at least one fixed anchoring zone;

a main mass able to move in rotation about an axis of rotation parallel to the plane of the substrate under the effect of a first mechanical stress along an axis Z perpendicular to the plane of the substrate. This main mass comprises two attachment zones symmetrical with respect to an axis X parallel to the plane of the substrate and perpendicular to the axis of rotation; and - Deformable elements connecting the two attachment zones to the anchoring zone, and allowing a displacement of the main mass around the axis of rotation.

According to the invention, the device further comprises at least one mechanical detection unit formed:

- An intermediate mass connected to the anchoring zone via mechanical connection means, allowing a displacement of the intermediate mass parallel to the plane of the substrate under the effect of a second mechanical stress inducing a displacement of the device according to the X axis; and

- A strain gauge extending perpendicular to the axis of rotation, the gauge being secured to the main mass via a first point of attachment and being secured to the intermediate mass via a second point of attachment.

Furthermore, according to the invention, the architecture of the intermediate mass and the positioning of the gauge are such that the displacements of the first point of attachment and the second point of attachment are of substantially identical directions and different amplitudes under the effect of the first bias, and substantially identical directions and substantially equal amplitudes under the effect of the second bias. In other words, the present invention proposes to integrate at least two sensitive masses each coupled to one end of the same strain gauge. One of the two masses is called the main mass, while the other is called the intermediate mass. These two masses are configured to have different sensitivities according to the mechanical stresses to which they may be subjected:

· The first mechanical stress, which is that which one wishes to measure, is in particular a pair oriented along the Y axis and tending to push the masses out of the plane. The main mass is sensitive, the intermediate mass is resistant. The gauge fixed between the two masses therefore undergoes constraints proportional to the amplitude of the displacement of the main mass, said displacement being itself proportional to the amplitude of the torque.

The second mechanical stress, which is that which one does not wish to measure, is in particular an acceleration along the X axis which induces displacements of the masses in the plane. The main mass and the intermediate mass are configured so that their displacements at the points of attachment of the gauge are of the same direction and same amplitude. Thus the gauge connecting the two masses is not subject to any constraint in response to the second mechanical stress.

· For all other types of mechanical stress, the main and intermediate masses are also insensitive, so no signal is measured by the gauges.

Thus, the main mass is configured to be the most sensitive to the mechanical stresses to be measured, so that the resistance variation (in the case of a piezoresistive gauge) representative of these mechanical stresses to be measured is the largest. The intermediate mass is itself configured to move with the main mass. In particular, the intermediate mass is configured to ensure a virtually zero resistance variation in response to transducer displacements along the X axis, while allowing a non-zero resistance variation of the gauges representative of the out-of-plane mechanical forces experienced by the transducer. .

More specifically, the intermediate mass and the connecting means provide an identical displacement, along the X axis, of the two points of attachment of the gauge. The gauge is in particular positioned so that, when the main mass undergoes the second mechanical stress which induces a displacement of the device in the direction along the X axis:

the first point of attachment of the gauge moves in the same direction as the second point of attachment of the gauge, and in particular in the same direction of displacement along the axis X that the principal mass in the absence of the first strength; and

- The amplitude of displacement in this direction along the X axis of the first point of attachment of the gauge is substantially identical to the amplitude of displacement in this direction along the X axis of the second point of attachment of the gauge. Thus, in the end, the gauge is not subjected to stress under the effect of the second mechanical stress, despite the movements of the main and intermediate masses under the effect of this second mechanical stress.

On the same principle, it is possible to use a mechanical resonator in place of the piezoresistive stress gauge, the resonant frequency variations of the resonator changing according to the constraints applied to it.

According to one embodiment, the device may further comprise two mechanical detection assemblies, the two gauges being subjected to opposite forces under the effect of the first mechanical stress, such as a force along an axis Z perpendicular to the plane of the substrate. In other words, if one of the gauges undergoes a tension in tension between its two points of attachment, the other gauge undergoes a compressive force between its two points of attachment. This embodiment makes it possible in particular to perform a differential detection and thus to obtain a better measurement accuracy.

The positioning of the attachment points of each gauge will depend in particular on the characteristics of the main and intermediate masses as well as the connection means used.

First, it is advantageous that the main mass has a volume greater than that of the intermediate masses. In practice, the intermediate masses are contained in the main mass, and the surface ratio between the main mass and the intermediate masses may be less than one third.

Moreover, the weights of each of the intermediate masses and the connecting means must preferably be adapted to ensure optimum sensitivity to displacements along the X axis of the main mass. According to a variant, the displacement of each of the intermediate masses under the effect of the second force may be a rotation in the plane around a pivot point defined by the connecting means. Because of this arrangement, the pivot point is fixed relative to the main mass. Furthermore, the connecting means used may be springs arranged to limit or prohibit any translation of the intermediate masses perpendicular to the axis of rotation and to allow only the rotation of the intermediate masses around their point respective pivot under the effect of an acceleration along the X axis. In addition, in this variant, each of the intermediate masses may have two portions in the direction of the axis of rotation of the main mass, the dimensions along the X axis are different. In particular, one of these portions, said thin portion, has a width in the direction of the X axis less than that of the other portion. Thus, the second point of attachment and the point of connection are preferably located on this thin portion.

In other words, each intermediate mass advantageously has a ream-like appearance having a most massive zone away from its point of attachment. Such a shape allows a nesting head-to-tail of the two oars to limit the area occupied by these intermediate masses and the widest portion constituting the shovel of the train allows to increase the weight of the masses.

According to another variant, the displacement of each of the intermediate masses under the effect of the second force can be a translation along the X axis.

Optionally, the device may comprise at least one stop capable of limiting the displacement of each of the intermediate masses in the direction along the X axis. In all cases, it is preferable for the gauges to be fixed to the main mass near its axis. rotation axis.

Various configurations are possible. For example, in one configuration, the two gauges can be arranged on either side of the axis of rotation of the main mass.

According to another configuration, for each of the gauges, the first point of attachment and the second point of attachment may be arranged, along the X axis, on either side of the axis of rotation of the main mass.

In addition, it is preferable that the distance along the axis X between the axis of rotation of the main mass and one or other of the points of attachment of the gauge is less than five times the length of the gauge. for example substantially equal to twice the length of the gauge, for example substantially less than twice the thickness of the substrate. The invention is particularly well suited for producing an off-plane detection accelerometer. In this particular case, the first mechanical bias is a pair oriented along the axis of rotation resulting from a Z acceleration applied to the device and the second mechanical bias is an acceleration along the X axis applied to the device. In addition, it may be advantageous to arrange the two intermediate masses in a symmetry along an axis perpendicular to the axis of rotation, for example in axial symmetry along the X axis. The invention is also well suited for the production of an off-plane detection magnetometer. In this particular case, the first mechanical bias is a pair oriented along the axis of rotation induced by the presence of a magnetic field oriented along the Z axis, and the second mechanical bias is an acceleration along the X axis applied to the axis. device. In addition, it may also be advantageous to arrange the two intermediate masses in a symmetry along an axis perpendicular to the axis of rotation. For example, according to a central symmetry around the center of gravity of the main mass.

In particular, in the case of a magnetometer, the main mass may further comprise:

two sensitive regions on either side of the axis of rotation of the main mass, these two regions being sensitive to the first force; and

an intermediate region between the two sensitive regions, this intermediate region being insensitive to the first force and containing the intermediate masses, the attachment zones, as well as the gauges.

In practice, the two sensitive regions of the main mass are covered with a magnetic layer to form a permanent magnet. Of course, the magnetic moment of this magnet must be oriented in a direction that allows the rotation of the main mass about its axis of rotation in the presence of a magnetic field oriented along the Z axis.

Preferably, the two sensitive regions are the image of each other by central symmetry. BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood on reading the description which will follow, given solely by way of example, and made with reference to the appended drawings in which:

FIG. 1 is a diagrammatic view in the plane of the substrate of a device according to one embodiment of the invention adapted for producing a magnetometer;

- Figure 2 is a schematic view in the plane of the substrate of a device according to another embodiment of the invention also adapted for producing a magnetometer;

- Figure 3 is a schematic view in the plane of the substrate of an intermediate mass coupled to a gauge according to a variant of the invention;

- Figure 4 is a schematic view in the plane of the substrate of an intermediate mass coupled to a gauge according to a variant of the invention;

- Figure 5 is a schematic view in the plane of the substrate of an intermediate mass coupled to a gauge according to a variant of the invention;

- Figure 6 is a schematic view in the plane of the substrate of an intermediate mass coupled to a gauge according to a variant of the invention;

FIG. 7 is a diagrammatic view in the plane of the substrate of a device according to one embodiment of the invention adapted for producing an accelerometer; and

- Figure 8 is a schematic view in the plane of the substrate of a device according to another embodiment of the invention also suitable for producing an accelerometer.

Note that in these figures, identical references are used to designate identical or similar elements. Moreover, the various structures presented are not at the exact scale, and only the elements essential for understanding the invention are shown in these figures for the sake of clarity. DETAILED DESCRIPTION OF DIFFERENT PARTICULAR EMBODIMENTS

A microelectromechanical device according to an embodiment suitable for producing an off-plane displacement magnetometer is illustrated in FIGS. 1 and 2.

This device or transducer, generally produced in a semiconductor substrate formed of parallel layers, comprises in particular a main mass 1 extending at rest, that is to say in the absence of any external force, parallel to the layers of the substrate or a plane called "plane of the substrate". This plane of the substrate is defined in particular by two perpendicular X and Y axes, and will be called later XY plane. One thus hears by displacements out-plan any displacement which is not contained in this plane XY.

The main mass is kept in suspension and is rotated about an axis of rotation 4 parallel to the Y axis via two deformable elements 31, 32 connecting two zones of fasteners 11, 12 of the main mass 1 to the less than a fixed anchoring zone 2. These deformable elements 31, 32 are, for example, silicon blades that deform in torsion under the effect of stresses out of the plane.

In the main mass, two regions are also identified called "sensitive regions" 13, 14 on either side of the axis of rotation of the main mass in the direction of the X axis separated from each other by an intermediate region 15 .

Each of these two sensitive regions 13, 14 is covered with a magnetic layer. In particular, the magnetic moment of each of these magnetic field sources is oriented so as to cause the rotation of the main mass around the axis of rotation 4 in the presence of a magnetic field to be measured oriented along an axis Z perpendicular to the XY plane.

Thus, when the device is immersed in the magnetic field to be measured, a mechanical torque, in particular a function of the magnetic moment of each of the sources, the amplitude of the magnetic field to be measured and the angle between the magnetic moment and the direction of the field to be measured, appears, and induces a rotation of the main mass about the axis of rotation 4 until the induced torque and the spring return torque equalize. The intermediate region 15 contains two intermediate masses 51, 52 substantially structurally identical, and mounted head to tail so as to limit the occupied area. Figures 1 and 2 illustrate two different ways of arranging the intermediate masses together.

As illustrated in FIG. 3, each intermediate mass 51, 52 comprises two portions in the direction of the axis of rotation 4. In particular, one of these portions, called the thin portion 511, 521, has a width in the direction of the X axis less than that of the other portion, said wide portion 512, 522.

These two intermediate masses 51, 52 are also coupled to connecting means 61, 62 and gauges 71, 72. More specifically, each connecting means 61, 62 is secured to the fixed anchoring zone 2 and to the one of the intermediate masses 51, 52 via a connection point 610, 620. These connecting means 61, 62 are in particular chosen to allow displacement of the intermediate masses 51, 52 in the XY plane when an acceleration along the X axis is applied to the transducer.

These connecting means 61, 62 are chosen and configured to allow a rotational movement of the intermediate masses 51, 52 around a pivot point formed by the connection point 610, 620. According to a variant, these connecting means 61, 62 may be chosen and configured to allow a displacement in translation of the intermediate masses 51, 52 in the direction of the X axis.

In practice, the connection point 610, 620 is located on the thin portion 511, 521 of the corresponding intermediate mass 51, 52 and positioned so as to allow a maximum of clearance of the wide portion 512, 522.

The two gauges 71, 72, in turn, extend perpendicular to the axis of rotation 4. Each of the gauges 71, 72 is secured to the main mass 1 via a first attachment point 711, 721 and is secured to one of the intermediate masses 51, 52 via a second point of attachment 712, 722. The second attachment point 712, 722 is located and positioned on the thin portion 511, 521 of the corresponding intermediate mass 51, 52, so that its displacements (i.e. those of the second attachment point 712 , 722) reflect those of the first attachment point 711, 721. In particular, the movements of the first attachment point 711, 721 and the second attachment point 712, 722 of the same gauge must be of substantially identical direction and of different amplitudes under the effect of a magnetic field oriented along the Z axis, and of substantially identical direction and substantially equal amplitudes under the effect of an acceleration along the X axis.

The positioning of the gauge is determined according to the theoretical calculations of displacement under an acceleration along the X axis of the main mass on the one hand, and the intermediate mass taken separately on the other hand, depending on the characteristics of these masses. and their springs. The optimal positioning is chosen for a minimal difference of these displacements.

In all cases, it is important that the gauges 71, 72 are fixed on the main mass near the axis of rotation 4. In particular, the distance along the axis X between the axis of rotation 4 and the either of the points of attachment of the gauge is preferably less than five times the length of the gauge, for example substantially equal to twice the length of the gauge.

Different configurations meeting these criteria are possible. For example, as illustrated in FIGS. 4 and 5, the two gauges 71, 72 can be arranged on either side of the axis of rotation 4. The first attachment point 711, 721 can be positioned as close to the axis of rotation 4 relative to the second attachment point 712, 722 (Figure 4), or be positioned further from the axis of rotation 4 relative to the second attachment point 712, 722 (Figure 5). According to another configuration illustrated in FIG. 6, the first attachment point 711, 721 and the second attachment point 712, 722 can be arranged along the X axis on either side of the axis of attachment. rotation 4. Another micro-electromechanical device according to another embodiment adapted to the realization of an off-plane displacement accelerometer is illustrated in FIGS. 7 and 8. This device differs from the device presented above by the fact that the main mass 1 does not contain magnetic regions, and that its shape has been optimized to limit its size.

Thus, similarly to the previous device, the device according to this other embodiment therefore comprises a main mass 1 and two intermediate masses 51, 52 contained in the main mass 1.

As before, the main mass extends in the plane XY and is rotatable about the axis of rotation 4 parallel to the axis Y. Two deformable elements 31, 32 connect two zones of fasteners 11, 12 of the main mass 1 to at least one fixed anchoring zone 2. Thus, an acceleration along the Z axis applied to the device induces a rotation of the main mass 1 around the axis of rotation 4.

The two intermediate masses 51, 52 are also substantially structurally identical, and are also mounted head to tail so as to limit the area occupied. Each of the intermediate masses has in particular an appearance in accordance with that illustrated in Figure 3 and already described above.

Similarly, each of these intermediate masses 51, 52 is also coupled to a gauge 71, 72 and to a connecting means 61, 62 for detecting and measuring a possible parasitic displacement of the main mass in the direction of the X axis, due to the application of an acceleration along the X axis.

As previously, each connecting means 61, 62 is secured to the fixed anchoring zone 2 and to one of the intermediate masses 51, 52 via a connection point 610, 620. These connecting means are also chosen to allow a displacement of the intermediate masses in the XY plane when an acceleration along the X axis is applied to the main mass. Furthermore, the connecting means 61, 62 may be chosen and configured to allow displacement in translation of the intermediate masses or a displacement in rotation around the connection point located on the thin portion of the intermediate mass. Similarly, the two gauges 71, 72 extend perpendicular to the axis of rotation 4. Each of the gauges 71, 72 is secured to the main mass 1 via a first point of attachment 711, 721 and is secured to the one of the intermediate masses 51, 52 via a second attachment point 712, 722 located on the thin portion of the intermediate mass. Of course, the different positioning criteria of the second attachment point and the different positioning configurations of the gauges presented above remain valid for this particular embodiment.

For example, to ensure a similar displacement in the X direction of the first and second attachment points of the gauge, the distance along the X axis between the axis of rotation Y and one or other of the points Attachment of the gauge is preferably less than five times the length of the gauge, for example substantially equal to twice the length of the gauge.

In the embodiments presented above the operation is substantially similar. Thus, in practice, under the effect of a mechanical stress to be measured induced for example by the presence of a magnetic field or by an acceleration along the Z axis, the main mass moves in rotation about the axis of rotation of the main mass. This rotation causes an opposite deformation of the gauges (in tension for one and compression for the other) and therefore resistance variations proportional to the applied stresses representative of the mechanical stress to be measured. Furthermore, under the effect of a parasitic mechanical stress along the X axis, induced in particular by an acceleration along the X axis, the main mass moves in translation along the X axis. Simultaneously with the translation of the mass main, each of the intermediate masses moves, in rotation or in translation according to the connecting means implemented, in the XY plane so as to follow the translational movement of the main mass so that each of the gauges is moved without suffering from deformation or stress representative of this parasitic mechanical stress. In other words, the assembly is configured so that both ends of a gauge move identically along the X axis, in terms of direction and amplitude, for limit any deformation of the gauge due to displacements in the plane XY of the device. Thus, the variation of the resistance of each of the strain gauges will be a function of the rotational displacements of the main mass about the axis of rotation, despite the presence of force inducing parasitic displacements along the X axis.

Finally, in the two embodiments presented, it is possible to provide stops 8 (a single stop has been shown in the figures) to limit the displacement of each of the intermediate masses along the X axis if this proved necessary .

Moreover, although embodiments implementing two intermediate masses have been presented above for differential mode operation, it is obvious that the solution of the invention can also be implemented with a single intermediate mass. and a single gauge, for common mode operation.

The present invention therefore makes it possible to produce off-plane detection type transducers incorporating in particular two or three mobile and sensitive masses, one of which is intended to detect, via strain gauges, the out-of-plane displacements induced by a force. to measure, the other mass or masses being intended to compensate for all the stresses exerted by the main mass on the gauges following its movements called "in the plane".

Claims

A microelectromechanical device made in a semiconductor substrate whose layers are parallel to a plane of the substrate, said device comprising:

at least one anchoring zone (2) fixed;

a main mass (1) able to move in rotation about an axis of rotation (4) parallel to the plane of the substrate under the effect of a first mechanical stress, said main mass (1) comprising two zones of fastener (11, 12) symmetrical about an axis X parallel to the plane of the substrate and perpendicular to the axis of rotation (4);

- deformable elements (31, 32) connecting the two attachment zones (11, 12) to the anchoring zone (2), and allowing movement of the main mass (1) about the axis of rotation ( 4);

characterized in that it further comprises at least one mechanical detection unit formed:

- An intermediate mass (51, 52) connected to the anchoring zone (2) via mechanical connection means (61, 62), allowing displacement of the intermediate mass (51, 52) parallel to the plane of the substrate under the effect of a second mechanical stress inducing a displacement of the device along the X axis; and

a strain gauge (71, 72) extending perpendicularly to the axis of rotation (4), said gauge being secured to the main mass (1) via a first point of attachment

(711, 721) and being secured to the intermediate mass (51, 52) via a second point of attachment (712, 722), the two points of attachment (711, 712, 721, 722) being configured so that the displacements of the first point of attachment (711, 721) and of the second point of attachment (712, 722) are of substantially identical directions and of different amplitudes under the effect of the first bias, and of substantially identical directions and of substantially equal amplitude under the effect of the second bias.

2. Device according to claim 1, comprising two mechanical detection assemblies, the gauges of the two mechanical detection assemblies being respectively subjected to tension and compression forces under the effect of the first mechanical stress.

3. Device according to claim 1 or 2, wherein each intermediate mass (51, 52) has two portions in the direction of the axis of rotation (4), one of said portions (511, 521), said thin portion. , having a width in the direction of the X axis less than that of the other portion (512, 522), the second attachment point (712, 722) and the point of connection (610, 620) being located on this fine portion (511, 521).

4. Device according to claim 2 or 3, wherein the intermediate masses (51, 52) of the two sets of mechanical detection are symmetrical to each other along an axis perpendicular to the axis of rotation.

5. Device according to one of claims 1 to 4, wherein the displacement of the intermediate mass or masses (51, 52) under the effect of the second bias is a rotation about a fixed pivot point defined by the connecting means (61, 62).

6. Device according to one of claims 1 or 4, wherein the displacement of the intermediate mass or masses (51, 52) under the effect of the second bias is a translation along the axis X.

7. Device according to one of claims 1 to 6, wherein the main mass (1) further comprises at least one stop (8) capable of limiting the displacement of each of the intermediate masses (51, 52) in the following direction the X axis and / or the Z axis.

8. Device according to one of claims 2 to 7, wherein the two gauges (71, 72) are on either side of the axis of rotation (4).

9. Device according to one of claims 1 to 8, wherein for each gauge (71, 72), the first point of attachment (711, 721) and the second point of attachment (712, 722) are arranged, along the X axis, on either side of the axis of rotation (4).

10. Device according to one of claims 1 to 9, wherein for each gauge (71, 72), the distance along the X axis between the first point of attachment (711, 721) and the axis of rotation ( 4) is substantially equal to twice the length of the gauge.

11. Device according to one of claims 1 to 10, wherein for each intermediate mass (51, 52), the distance along the axis X between the axis of rotation (4) and one or the other of Gauge attachment points are substantially less than twice the thickness of the substrate.

12. Device according to one of claims 1 to 11, wherein:

the first bias results from an acceleration along the Z axis or from a magnetic field along the Z axis; and

the second bias results from an acceleration along the X axis.

13. Device according to one of claims 1 to 12, wherein the main mass (1) comprises:

- two sensitive regions (13, 14) on either side of the axis of rotation (4), said two regions being responsive to the first force; and

an intermediate region (15) between the two sensitive regions (13, 14), said intermediate region being insensitive to the first bias and containing the two zones of fasteners (11, 12) and the first attachment points (711, 721) of the gauges (71, 72).

14. Device according to claim 13, wherein the two sensitive regions (13, 14) are the image of each other by central symmetry.