FIELD OF THE INVENTION AND PRIOR ART
The present invention fits in the technical field of electromechanical devices, including MEMS (Micro Electro-Mechanical Systems) or NEMS (Nano Electro-Mechanical Systems), in particular those comprising the variable components of millimeter dimensions, micrometric or nanometric electrically biased, such as sensors or actuators electrostatic.
It is common to operate of attraction or repulsion forces, including electrostatic interactions, for making an electrical function, such actuation or detection, within MEMS devices. Simple forms of electrostatic actuators, comprising two electrodes comprising at least one flat area and facing each other, which is applied to a different voltage, are known per se. It is also known to use interdigitated combs as electrodes in such an actuator, for example to cover a larger displacement amplitude.

A major failure modes of the MEMS or NEMS electromechanical devices is the bonding of movable elements, in particular by forces of Van der Waals or electrostatic interaction of moving members differently polarized. A failure mode to avoid is the micro-arcing: an electrical arc can occur when the moving elements differently polarized are polarized by * high levels of potential (typically several tens of volts), and / or when the movable elements are little remote from each other (typically one micrometer or less). Moreover, these mobile elements and surrounding components may be damaged by severe shocks and / or repetitive.

To overcome these problems a known solution, for two such movable planar elements arranged on the same plane, is to implement rigid stop members or flexible mechanically strong on the area where said elements

Mobile may get in touch. The adhesion forces, which depend on the contact surface, are therefore limited.

However, contacting with a stopper having a certain polarity with a different polarity element may generate a current flowing through and electrostatic discharge, which may compromise the functionality of the actuator or even irreversibly damage. The risk of micro arcing is not completely prevented. It has therefore been proposed to electrically isolate such a stop of the movable element from which it protrudes, so that its contact with the facing member (the abutment) does not present a risk of electrostatic discharge gluing or electrostatic.

Patent application US 2015/0033849 A1 describes a device that can be implemented in a MEMS inertial sensor, comprising a flat mobile mass and a sensing plate parallel opposite. The moving mass and the detection plate are placed at different electrical potentials. To avoid electrostatic discharge events during acceleration or shock by moving the moving mass, the detection plate has abutment elements oriented in a direction substantially perpendicular to the plane of the sensing plate. Said stop elements are electrically insulated from the sensor plate and placed at the same potential as that of the moving mass compared. However, this solution is only relevant if the relative movement of the movable elements is out of plane,

PRESENTATION GENERAL DE INVENTION

The present invention provides an appropriate solution for two coplanar planar electrodes located on the same layer in a MEMS or NEMS device, movable with respect to one another along at least one first direction of movement within the plane of the electrodes, the electrodes to be placed at different potentials.

The solution of the invention provides the mechanical functioning of these two elements movable relative to one another, while preserving their functionality electromechanical, after a vibration or shock event causing their movement in the plane.

In addition to a first planar layer comprising two components of which at least one mobile polarized differently (typically electrodes) and providing between them the electromechanical functionality required, it is proposed to implement an additional layer electrically insulated from the first, comprising movable members relative to the other, mechanically integral with the two elements of the first layer, which can be moved in their plane and abut one against the other.

The invention aims to avoid direct contact between two differently polarized components of which is to preserve function and even prevent said elements are close enough to generate a phenomenon of micro-arcing. Therefore, the mechanical strength and electrical said elements is ensured even in case of vibration or shock event, and even if said elements are formed of brittle materials.

The risks associated with electrostatic interactions are so limited with a simple and reliable implementation, adapted to a microscale or nanoscale device, for the sake of miniaturization of such a device.

Thus, the invention relates to a MEMS or NEMS type sensor or actuator device comprising a stack including a first planar layer comprising two electrode plates to be placed at different electrical potentials, the first electrode being movable in the plane in relation to the second electrode in a first direction parallel to the first planar layer and a second superimposed planar layer to the first, electrically insulated from the first layer by at least one intermediate layer formed of insulating material, the second planar layer comprising a first planar member secured mechanically from the first planar electrode and a second planar member mechanically secured to the second planar electrode.

The second layer further comprises a stop element protruding from any one of these two elements according to drawings the aforementioned first direction, the stop element being intended to be at the same electrical potential that a surface opposite belonging to the other planar members. The stop can come into contact with said surface of the planar member opposite and block the approximation of two planar electrodes of the first planar layer in the first direction during a solicitation, in order to prevent them from being too relatives.

Advantageously but not limited to, in an unloaded condition as in the factory, the stack is arranged so that, if we consider the free excursion distance of the abutment between the abutment element and planar member opposite, according to the aforementioned first direction of movement of the electrodes, said free excursion distance is less than the minimum distance between any free end of the first planar electrode and a nearest end of the second electrode plate, taking according to the same first direction.

The abutment member can then, at an event inducing a relative movement of the two electrodes according to the same first direction, stop said relative movement of the two electrodes before the first electrode is contacted with the second.

Optionally, at least one of the planar electrodes of the first layer is made at least partially deformable in the first direction. An electrode arrow distance is defined as the maximum deformation of the deformable electrode in this same direction, or the sum of the maximum deformation . two electrodes, if the two electrodes are made deformable in the first direction. The minimum distance between the electrodes is then made greater than the sum of the distance of arrow electrode and the first distance of free excursion of the electrodes.

Optionally, and cumulatively or not with the deformability of electrodes, at least one of the second layer of planar elements is made at least partially deformable in the first direction. A distance arrow

Plan element is then defined as the maximum deformation of said planar member (e.g., the stop if said planar member carries a stop) in this same direction, or the sum of the maximum deformation of the two planar members, if both plane elements are taken deformable in the first direction. The minimum distance between the electrodes is then made greater than the sum of the distance of planar element boom and the first free excursion distance of the electrodes.

In one particular embodiment, where one of the two planar elements is partially deformable in the first direction, the second planar layer is pierced with a cavity (non-through, which does not cross the full stack), practiced in the anchor of the stop. According to another implementation, which may or may not be combined with the first, the second planar layer is pierced with a non-through cavity, along the outer edge of the backing (surface facing the abutment). In both implementations, the distance of arrow yaws elements is the sum of dimensions of the two cavities, or the dimension of the single cavity if only one cavity is used.

According to another implementation, wherein the first planar member carries a first stop element (e.g. in the form of beam) and the second planar member carries a second element similar stop, the two flat electrodes and the two planar elements are deformable according to first direction. The deformability is obtained by two emergent cavities which pass through the stack, a first being formed to anchor the first stop, in correspondence in the first direction with the first stop but not with the second abutment, forming a first flexible blade ,

a second being formed to anchor the second stop, in correspondence in the first direction with the second stop but not with the first abutment, forming a second flexible blade.

The first free excursion distance is then defined as the minimum distance between one of the stops and the counter-abutment. The electrode arrow distance is then the sum of dimensions of the two emergent cavities.

In a variant of this latter implementation, where it retains the same first and second stop members,

a first opening cavity is formed in the first planar electrode, in correspondence in the first direction with one end of the second abutment, forming a first flexible leaf,

and a second opening cavity is always formed in the first planar electrode, anchoring the first stop element, in correspondence in the first direction with the first stop. The two emergent cavities are thus performed side-by-side to form two juxtaposed flexible blades.

The first free excursion distance is then defined as the minimum distance between one of the stops and the opposite surface in the second layer.

Optionally, for example in relation to the two last above-mentioned implementations, the two electrodes are also movable with respect to each other in a second direction substantially perpendicular to the first direction, the second direction being parallel to the layers of the stack. The first planar member comprises a first stop and the second planar member comprises a second stop. The stack is then configured so that in the unloaded state, the entire free end of the first planar electrode is located, relative to the second electrode plate at an upper minimum distance to a second free excursion distance corresponding in the second direction, the second distance d '

So advantageous but non-limiting, one electrode comprises a flat plate.

So advantageous but non-limiting, one electrode comprises an electrostatic comb.

PRESENTATION DES FIGURES

Other features, objects and advantages of the present invention will become more apparent in the particular embodiments described below, and the view of the following figures, which must be interpreted in a purely illustrative and not restrictive.

Figure 1 is a schematic view of a stop stack according to a first embodiment, wherein the stacking of the electrode plane is viewed from above.

Figure 2 shows the device illustrated in Figure 1, a view in section on a plane perpendicular to the plane of the stack, the plane of section being indicated by the axis A.

Figure 3 shows the device shown in Figure 1, exploded perspective view from above.

Figure 4 is a schematic view of a stack abutment according to a variant of the first embodiment wherein the electrodes of the stacking plane is viewed from above.

Figure 5 shows the device illustrated in Figure 4, a view in section on a plane perpendicular to the plane of the stack, the plane of section being indicated by the axis A.

Figure 6 shows the device shown in Figure 4, seen in exploded view from above.

Figure 7 is a schematic view of a stop stack according to another variant of the first embodiment, wherein the stacking of the electrode plane is viewed from above.

Figure 8 shows the device illustrated in Figure 7, a view in section on a plane perpendicular to the plane of the stack, the plane of section being indicated by the axis A.

Figure 9 shows the device shown in Figure 7, seen in exploded view from above.

Figure 10 is a schematic view of a stop stack according to a second embodiment, wherein the stacking of the electrode plane is viewed from above.

Figure 11 shows the device illustrated in FIG 10, in a sectional view in a plane perpendicular to the plane of the stack, the plane of section being indicated by the axis A.

Figure 12 shows the device shown in Figure 10, seen in exploded view from above.

Figure 13 is a schematic view of a stop stack according to a variant of the second embodiment, wherein the electrode stack plane is viewed from above.

Figure 14 shows the device illustrated in Figure 13, a view in section on a plane perpendicular to the plane of the stack, the plane of section being indicated by the axis A.

Figure 15 shows the device shown in Figure 13, seen in exploded view from above.

DETAILED DESCRIPTION OF EMBODIMENTS

There is shown in Figures 1 to 3 a first embodiment of a stop stack layers in a MEMS or NEMS device.

The stack is viewed from above in Figure 1, according to a viewing axis perpendicular to the stack. It is seen from the side in Figure 2, in section along a plane perpendicular to the plane of the stack, materialized by the axis A in dashed lines in Figure 1 and by the two axes A dotted in Figure 3. Finally, is an exploded perspective view from above in Figure 3, indicating two directions parallel to the direction A to include the section taken in figure 2.

On a first layer 1 overlying, a left electrode 10 comprises a flat left portion in one piece, and a straight portion forming an integral electrostatic comb from the left side. The left electrode 10 is considered movable only in a first direction by the axis A. On the left electrode 10, a straight line 1 1 is similar electrode design, with a flat straight portion of a integrally and a left portion two lateral symmetrical electrostatic combs that may come into electrostatic interaction with the comb electrode 10. the right electrode 11 is considered here fixed.

For this first embodiment, when we speak of a displacement of the relative 10 or moving electrode of the two electrodes 10 to 1 1, it would take only a displacement in the first direction indicated by the axis A. The two electrodes 10 to 1 1 are for example made of silicon. In this embodiment, they are considered non-deformable in direction A.

The left electrode is polarized differently from the electrode on the right, so that contact between the one end of the electrode 10 and to one end of the electrode 1 1 may cause a short -Circuit and / or electrostatic discharge, which can permanently damage the stack stop or the control electronics / playback due to the generated short circuit. In addition, default risks exist even if the electrodes 10 and 11 are not brought into direct contact, but are spaced a short distance (micrometer), low enough to create a disruptive field in the air and cause micro arcing phenomenon.

A layer 3 is an electrically insulating intermediate layer. This layer is placed under the layer 1 and is visible only in Figures 2 and 3. Within this layer was placed a flat insulating surface left under the flat left portion of the electrode 10, and an insulating surface straight planar plane in the right part of the electrode 11. the central part of the diaper 1 comprising a comb teeth of alternating electrode 10 and the comb electrode 11 is left without underlying insulating member in the layer 3.

Under the layer 3 there is arranged a layer 2 of semiconductor. It is this sub-layer 2 which comprises a stop element. A movable member plane 20 on the left is disposed in correspondence of the left electrode 10. Here, the movable member plane 20 is of the same width in a direction perpendicular to the direction A, that the electrode 10. Element mobile 20 extends over a greater distance to the right of Figure 1, towards the electrode 11 facing each other, the right edge of the flat left portion of the electrode 10. Thus, the movable member 20 s' extends to the right until a stop element 24, integral with the movable member 20 forming its outer right edge. The abutment member 24 does not necessarily extend across the entire width of the movable member 20 and the electrode 10.

The stop 24 thus projects outside the movable member 20 in direction A. Here, the stop 24 is located directly above the electrode 10 including comb which protrudes from said electrode. However, alternatively, the stop 24 may protrude from the movable element 20 at a location that is not located under the comb. The stop 24 could for example be located under the left side of the electrode 10 full.

Another important property of the system is that the movable member 20 is secured mechanically to the electrode 10, in particular in its translational movement in direction A. In its translation movement along this direction, the movable member 20 and the electrode 10 are held by suspension means 5 are implemented on the one hand in the first layer 1 and secondly in the second layer 2 (but not in the insulating layer 3). These suspension means 5 allow the electrode 10 and the planar member 20 to translate, being mechanically fixed with respect to a fixed portion of the MEMS device located behind the suspension means 5.

The planar insulating surface layer 3 left and makes the electrode 10 mechanically secured to the movable member 20. It also creates an electrical isolation between the electrode 10 and the movable member 20, to ensure that the

electric potentials of the elements 10 and 20 are independent of any position of the assembly formed by the elements 10 and 20 in direction A.

Within the layer 2 facing the movable member 20 including the stopper member 24 is arranged a movable member plane 21 on the right, arranged in vertical correspondence with the right one electrode 1. Similarly as the movable member 20 to the left, the movable member 21 extends over a greater distance to the left, towards the electrode 10, the planar portion right of the right electrode 11, by its left edge 23. the movable member 21 is integral with the electrode 1 1, in particular in its translational movement in direction A. the straight planar insulating surface layer 3 is preferably also secured to the electrode 11 and the element mobile 21.

The left edge 23 is therefore opposite the abutment member 24 at a distance D B of the stopper member 24 in the direction A, the distance D B being here a first free excursion distance.

The first free excursion distance D B corresponds to the maximum amplitude of displacement in the first direction A of the stopper 24 relative to the movable member 23 (and thus, the left electrode 10 with respect to the right electrode 11). During an impact event which causes a displacement of the movable element 20 relative to element 21 and electrode 10 relative to electrode 11, the stop element 24 interrupts the approximation in the direction to these elements by abutting against the right edge 23, to ensure that the electrode 10 is not in this state of closest approach at a distance from the electrode 1 1 lower than a distance D2. The distance D 2of closest approach between the electrode counted tienf the risk that micro arcing phenomenon occurs between adjacent ends of the two electrodes 10 and 11. This distance D 2 depend on the implementation of conditions, including the potential levels set work at the electrodes 10 and 11. It is typically of the order of one micrometer. This distance D 2 is not visible in Figures 1 to 3. The minimum Dmin distance between the electrodes 10 and 11 in an unloaded state (ie out of the state of closest approach) is thus greater than the amount taken of the first distance of free excursion DB in the first direction A, and the distance D 2 depending on implementation conditions. This distance D min entre

the electrodes 10 and 11 in direction A is, in this example, performed between the right edge of the tooth 101 of the comb electrode 10 and the left edge of the tooth 102 of the comb electrode 11, the reference 101 and 102 being visible in Figure 2 of the present application. The electrodes may comprise for example, conventional electrostatic combs of small dimensions, it may be necessary to implement a very low free excursion distance, typically of the order of 5 microns.

Also significantly, the contact between the abutment element 24 and the left edge 23 of the movable upright member 21 should not present the same risks of a short circuit, electrostatic discharge or electrostatic bonding that the contact between two free ends of electrodes 10 and 1 1, such as ends 101 and 102. in the example presented here, all components of the undercoat layer 2 are polarized in the same manner. The insulating intermediate layer 3 ensures independence between the electric potential of the layer elements 1 and the electric potential of layer 2 components, although there are dependencies between the positions in the direction A of some of these elements.

There is shown in Figures 4 to 6 a first variant of the first embodiment of Figures 1 to 3. As in Figures 1 to 3: the stack is viewed from above in Figure 4, according to a line of sight perpendicular to the stack on the side in Figure 5, in section along a plane perpendicular to the plane of the stack, materialized by the axis a in dotted lines, and finally seen in exploded perspective view from above in Figure 6.

The implementation of the layers 1, 2 and 3, electrodes 10 and 11 and the corresponding flat elements 20 and 21, is similar to that shown in Figures 1 to 3. The implementation of the stop 24 protruding from the planar member 20 is also similar, except that the stop is made flexible compared to the preceding embodiment. Here, a cavity 26 is made at the anchorage of the abutment element 24, with a slightly lower than the right outer edge of the planar member 20. The cavity 26 is not formed over the entire width of the planar member 20, but it must be formed on a strictly greater width than the stop element 24, to ensure the mobility of the abutment 24 with respect to the planar member 20 in the direction A. the cavity 26 as well, on either of side of the stop 24, two free embedded blades. The stop 24 is also not deformable in a direction perpendicular to the A direction (vertical in the figure), since it is held by the two recessed royalty either side of the abutment 24. The abutment blade ( surface 23 opposite the abutment 24), it remains dimensionally stable in the direction A. It should be noted that the flexible stopper 24 is here formed by two free embedded blades, but may be implemented in any other manner known in the electromechanical devices (chevron ...)

The two planar members 20 and 21, and with them electrodes 10 and 11 mechanically linked to said planar members can be moved towards one another in response to a solicitation, held by the suspension means 5. If the approximation is enough, the stop 24 can get in touch with the surface 23 opposite and plans elements 20 and 21 can still move closer under the effect of the leftward movement of the flexible blade, the cavity 26 is then closed. The cavity 26 is formed only in the second planar layer, since the first planar layer is not full in the area located vertically above the cavity 26 (zone electrostatic comb electrode). The cavity 26 is of a dimension in the direction A which corresponds to a distance of arrow DFP planar member,

Thus, in response to a request, the electrodes 10 and 11, and in particular the tooth 101 of the comb electrode 10 and the tooth 102 of the comb electrode 11, may approach a maximum distance D B(first free excursion distance) to which is added the distance of arrow DFP- planar member The dimensioning of the stack is, in this variant of the first embodiment, performed so that the minimum distance in Dmm an unstressed state between the electrodes 10 and 11 in the direction a, made for example here between the teeth 101 and 102, is greater than the sum of the distances DB and DFP. Thus, it is ensured that even when loaded would generate an approximation of the electrodes 10 and 1, the teeth 101 and 102 are not likely to touch. One might also consider a distance D 2 micro-arcing in below which it believes there is a risk that a bow

Power is formed in the thin layer of gas between the teeth 101 and 102. In this case, the distance should be taken Dmm greater than DB + DFP + D 2 , so that even in a state where the two electrodes 10 and 11 are close together a failure related to micro-arcing is avoided.

In Figures 7 to 9, there is shown a second variant of the first embodiment of Figures 1 to 3. As in Figures 1 to 3: the stack is viewed from above in Figure 7, according to a line of sight perpendicular to the stack on the side in Figure 8, in section along a plane perpendicular to the plane of the stack, materialized by the axis a in dotted lines, and finally seen in exploded perspective view from above in Figure 9.

In this variant, the shape of the electrodes of the layer 1 and the stop 24 is similar to that described in relation to Figures 1 to 3.

As in the first variant described above, is introduced a flexible blade in the layer 2 to induce partial deformability in the first direction A. However, unlike the first embodiment described in Figures 4 to 6, it is convenient not a cavity in the anchoring of the abutment 24. Here we practice a cavity 27 in the planar member 21 in the region facing the stop 24 (that is to say in the region of the abutment) . With a slightly lower than the left outer edge of the movable plane member 21, an elongated cavity is made, over a width along the direction perpendicular to the direction A which is less than the total width of the planar member 21 but greater the width of the abutment member 24 so as to form a bi-recessed flexible blade, the part of the

The two planar members 20 and 21, and with them electrodes 10 and 11 (mechanically linked to said planar members) can again be moved towards one another in response to a solicitation, held by the suspension means 5.

If the approximation is sufficient, the stop 24 can get in touch with the surface 23 opposite and plans elements 20 and 21 can still move closer under the effect of the rightward movement of the flexible blade, the cavity 27 being then closed. The cavity 27 is again formed in the second layer 2, and is of a size which corresponds to a distance of planar element arrow D F p, as shown in Figure 5. This distance arrow of planar member represents the maximum deformation of the planar member 21 in the direction A.

Thus, in response to a request, the electrodes 10 and 11, and in particular the tooth 101 of the comb electrode 10 and the tooth 102 of the comb electrode 11, may approach a maximum distance DB ( first free excursion distance) to which is added the distance arrow DFP planar member. The minimum distance D m i nin an unloaded condition between the electrodes 1 and 10 in the direction A, made for example here between the teeth 101 and 102, is greater than the sum of the distances DB and DFP. If it is desired, optionally, take account of the risk of failure associated with a micro-arcing, one can define a minimum distance D2 between the ends of electrodes in below which said risk exists. then dimensionnerait the stack so as to have Dmin greater than the sum of + DFP + D2.

There is shown in Figures 10 to 12 a second embodiment of a stack in layers, where the implementation of the electrodes and of the stops is different with respect to all the previously described figures. here shows the electrodes 10 'and 11'.

The stack is viewed from above in figure 10 according to a viewing axis perpendicular to the stack. It is seen from the side in Figure 11 in section along a plane perpendicular to the plane of the stack, materialized by the axis A in dashed lines in Figure 10 and by the two axes A dotted in Figure 12. Finally, it is seen in exploded perspective view from above in Figure 12, which shows two directions parallel to the direction A to include the section taken in Figure 11.

The reference numerals used in Figures 1 to 3 and defined above can be reused in the Figures 10 to 12 to designate corresponding elements in the stack according to the second embodiment.

This second embodiment differs in particular from the first embodiment in that the electrodes 10 'and 1 1' of the layer 1 and the planar members 20 and 21 are taken corresponding partially deformable in the first direction A. Here we propose an implementation advantageous for electrostatic combs visible on the electrodes 10 to 12 are movable in the direction A relative to the remainder of the electrodes wearer.

Moreover, this second embodiment also differs from the first embodiment in that the electrodes 10 'and 11', including electrostatic combs are movable relative to one another in a second direction B perpendicular to the direction A, contained in the plane of the electrodes 10 'and 11'. For example, not shown suspension means in the figures, for example similar to the suspension means 5 may allow the mobility of the electrodes 10 'and 11' in the direction B.

The left electrode 10 'of the layer 1 comprises here a planar portion and a left electrostatic comb on a straight portion. Symmetrically, the right electrode 11 'comprises a right flat portion and an electrostatic comb on a left portion. Both electrostatic combs respectively corresponding to the electrodes 10 'and 11' are arranged such that in an unloaded condition, their teeth interlock without touching, and in particular without contact in the first direction A or in the second direction B.

The left electrode 10 'differs from the left 10 of the previous embodiment in that electrode of the left flat portion is pierced with a through cavity 12 of rectangular shape. It is called through-the sense that it is performed over the entire thickness of the stack, in the three layers 1, 2 and 3. This embodiment thus differs significantly, the embodiments corresponding to Figures 4 to 9, wherein a cavity is practiced in the lower layer 2, the electrodes 10 and 11 thus being non deformable in the direction A. the through-cavity 12 is practiced to

vicinity of the right outer edge 14 of the left flat portion of the electrode 10 ', but by allowing some back relative to the edge 14. This cavity allows the outer edge 14 to form a flexible blade. The flexible blade may respond to a vibration event suffered by the electrode 10 'by moving in translation in the direction A, a maximum amplitude which corresponds to a distance of arrow DFE electrode, and a boom distance Plan element D Fp (since both a portion of the electrode 10 'and a part of the planar member 20 can be deformed at the flexible blade). When the flexible blade 14 moves in such a translation, the material of the portion of the electrode 10 'forming electrostatic comb being also not deformable in the direction A, the electrostatic comb is likely to also move in translation in the direction a on an amplitude which does not exceed the distance of arrow D electrode F E. the flexible blade 14 is also not deformable in the direction B, as maintained by the edges of the outwardly opening cavity 12.

So quite similar, the right electrode 11 'is provided on the left outer edge of the planar portion straight line a through cavity 13 which results in a flexible strip 15. The flexible strip 15 is as well as the flexible blade 14, deformable in translation in the direction a, with a maximum amplitude equal to the distance of electrode arrow DFE-

La distance Dmin between the electrodes 10 'and 11' in the direction A is, in this second example, performed between the right edge of the tooth 101 'of the comb electrode 10' and the left edge of the tooth 102 'of the comb the electrode 11 ', reference numbers 101' and 102 'being visible in Figure 11. the electrodes 10' and 11 'being polarized differently "as in the previous example, it is essential that they are not in contact at jeopardize the electromechanical system functionality. It may possibly consider that it is not enough to prevent the electrodes contact, and it is also necessary to prevent the ends from being too close (about the distance of micrometers, for example) to avoid micro-arcing of the phenomena. The intermediate layer 2 here ensures an electrical insulation similar role to that it plays in the above example. Finally, the layer 3 comprises, similarly to the previous example, a stop member which ensures that the

electrodes 10 'and 11' are not likely to get in touch at a vibration event or shock susceptible to moving the electrodes 10 'and 11' relative to each other along the first direction A .

The underlayer 2 is shown here with a different arrangement of the previous example. The underlayer 2 always includes a left planar member 20 'secured to the electrode 10' and a right planar member 21 'secured to the electrode 11', such as plans elements 20 'and 21' are movable 'with respect to each other in the first direction A.

Unlike the element plane left 20 illustrated in Figures 1 to 3, the left plane element 20 'of this example changes in width in the vicinity of the outer edge 14 of the electrode 10'. It has a leg 24 forming a stop member, extending to a right end of stopper member 22 '. The abutment member 24 is not, like in the previous example, the center position in the area between the plane of the left member and the right member in the plane of the undercoat layer 2, but is located on the right edge of the branch 24 which is slightly recessed relative to the edge 23 opposite of the right plane element 21 '.

As shown in Figure 10, 24 and the stop member including its end 22 'are located in the extension in the first direction A of the outwardly opening cavity 12, but not in the extension of the outwardly opening cavity 13 with, so that facing the end 22 'is a non-deformable part of the element on the right 21'. In addition, the width of the outwardly opening cavity 12 (in direction B) is greater than that of the stopper 24. Thus, the anchoring of the abutment 24 corresponds to a flexible blade in the direction A, but the end 22 'is not face a flexible blade.

Symmetrically, the right member 21 'has a stop member 25 extending from the corresponding edge vertically to the outer edge 15 of the electrode 11', and in the extension of the outwardly opening cavity 13, and has a member end abutment facing a non-deformable edge of the left element 20 '. The stop stack according to the second embodiment therefore comprises two stop elements 24 and 25.

The distance between the abutment element 24 and the edge 23 'of the right plane element 21' facing each other, or between the abutment element 25 and the edge of the left plane element 20 'opposite correspond a first free excursion distance DB, the same significance as the first free excursion distance D Bin the previous example. Note also here that the distance of arrow DFE electrode (maximum total deformation at the electrodes), which is the deflection distance due to the cavities 12 and 13 in the layer 1, and the distance of planar element arrow DFP (maximum total deformation at the stop elements), which is the deflection distance due to the cavities 12 and 13 in layer 2, are equal. The lead-through cavities 12 and 13 are of constant dimensions over the entire thickness of the stack: the anchoring of electrostatic combs is deformable in the direction A of the same length as the anchor stops.

Importantly, the first free excursion distance DB, which corresponds to the maximum amplitude of displacement in the first direction A of the end 22 'to the next element 23' (and therefore of the left electrode 10 'to the right electrode 1) is such that the amount of this free excursion distance and the maximum strain amplitude (distance from arrow DFE electrode) of the two electrodes 10' to 1 1 'relative to the other is less than the minimum distance in the direction a between the left electrode 10' and the right electrode 11 '.

Thus, when the two electrodes 10 'and 11' are close under the effect of an internal force (electrostatic force) or external (acceleration, shock), the teeth electrostatic combs, (e.g., the teeth 101 'and 102 ') first approach to a distance which corresponds to the free excursion of the stop elements 24 and 25. Then if the approximation continues, the base of the abutment member 24 may, under the effect support of the end 22 opposite the abutment 24, press against the flexible plate 14 located at the anchorage of the abutment 24, and induce deflection of the comb teeth 10 '.

The design criteria applied here is thus more restrictive than that of the previous example, for in the dimensioning of the minimum distance between

the two electrodes 10 'and 1 1' in the first direction A, takes into account not only the first free excursion distance of the electrodes 10 'and 11' enabled by the arrangement of the stop 24, but also the amplitude maximum relative deformation of the two electrostatic combs being respectively projecting electrodes 10 'and 11'. Thus, the distance Dmin between the two electrodes 10 'and 1 1' in the first direction A, shown here between the tooth 101 'of the comb electrode 10' and the tooth 102 'of the comb electrode 11', must be greater than DB + DFE. If it is desired to take account of risks of micro-arcing between the teeth of electrostatic combs of electrodes 10 'and 11', one can define a distance D 2minimum between the ends of electrodes in below which the risk exists. Then dimensionnerait the stack so as to have D min greater than the sum D B + DFP + D 2 .

One effect of this design is to allow, during an impact event which causes a displacement of the movable member 20 'to the element 21' and electrode 10 'to electrode 11' that the stop element 24 interrupts the approximation according to the direction a of the elements abutting against the right edge 23 ', until the electrode 10' can not be sufficiently close to the electrode 11 'for generating a discharge electrostatic or electrical micro-arcs, and damage the MEMS device.

Moreover, as mentioned above, the electrodes 10 'and 11' are movable with respect to each other not only in the first direction A, but also in the second direction B perpendicular to the decision here first direction A. the two stop elements 24 and 25, the shape and positioning Rappert the planar members 20 'and 21' have been described above, are spaced from each other according to this second direction B , leaving a second free excursion distance DB 'in the direction B.

The stack is then arranged such that in the unloaded state, the first electrode 10 'is at a distance Dmin' to the second electrode 11 'in the second direction B which is greater than the second distance d free excursion DB 'so that the two electrodes can not be contacted by an approximation according to the second direction B.

A second design criterion D m i n '> DB' is here taken into account, in addition to the criterion which governs the maximum displacement of the electrodes and their dimensioning in the first direction A.

An advantage of this second embodiment with partial deformability of the electrodes is to be used for devices susceptible to large amplitudes vis-à-vis the air gap of the electrodes following movement to a shock event. In particular, MEMS for high performance applications require small dimensions and high masses gaps, typically inertial sensors, which generate a large amount of movement due to a shock event, compared to the gap between the electrodes.

There is shown at 13 to 15 a variant of the second embodiment of Figures 10 to 12.

The stack is viewed from above in Figure 13, according to a viewing axis perpendicular to the stack. It is seen from the side in Figure 14 in section along a plane perpendicular to the plane of the stack, materialized by the axis A in dashed lines in Figure 13 and by the two axes A dotted in Figure 15. Finally, it is seen in exploded perspective view from above in Figure 15, which shows two directions parallel to the direction A to include the section taken in Figure 14.

In this variant of the second embodiment, the shape of the electrodes of the diaper 1 is similar to that described above in connection with Figures 10 to 12. The shape of the stops 24 and 25, in the layer 2, is also unchanged.

However, in this variant, only the electrode 11 'is partially deformable in the first direction A, the electrostatic comb of this electrode being movable in the direction A with respect to its base. Moreover, the electrodes 10 'and 11' are movable with respect to each other in a second direction B perpendicular to direction A, contained in the plane of the electrodes.

Specifically, the opening cavity 12 described in relation to Figures 10 to 12, formed in the electrode 10 'and the underlying layers, is no longer practiced here. The opening cavity 13 of Figures 10 to 12 is not present in the variant of Figures 13 to 15. The stack here described comprises two emergent cavities 13 'and 13 "carried with the same back from the left outer edge of the electrode 11 ', of width in the direction B higher than the ends of the abutment members 24 and 25 so as to form two flexible blades 15' and 15 "in the first direction A.

The opening cavity 13 'is situated opposite the end 22' of the abutment member 24 (the shape of the stop element 24 being identical to that of the second embodiment shown here). The opening cavity 13 ", it is practiced in the anchoring of the abutment member 25. The two emergent cavities 13 'and 13", and therefore the two flexible blades 15' and 15 "are independent and separated by a rigid wall. Furthermore, the stop elements 24 elongate and 25 are unchanged compared to the second above described embodiment.

Thus, when the two electrodes 10 'and 1 1' are similar in the first direction A under the effect of an external mechanical stress, the teeth of the electrostatic combs (e.g., the teeth 101 'and 102') approach of first to a distance which corresponds to the first free excursion distance D B of the stop elements 24 and 25, as in the first implementation of the second embodiment.

In contrast, the behavior of teeth differs electrostatic combs when the approximation in the first direction A is continued, the base of the stop element 24 can no longer induce a deflection of the comb teeth 10 'in the absence of the opening cavity 12 of the implementation mode of figures 10 to 12.

Instead, the presence of a new opening cavity 13 'opposite the end 22' of the stop element cavity in the body of the electrode 11 'facing each other, that the end 22' of the abutment 24 can press against the flexible blade 15 ', so that the stop 24 continues its progression towards the electrode 1 Γ in the first direction A. Thus, the comb teeth 10' may be bent in opposite direction to the direction deflection obtained for the second embodiment. The deflection obtained in this third embodiment is, unlike that obtained in the second embodiment, not such as to bring the teeth of the electrostatic combs such as teeth 101 'and 102'.

The design criteria applied here is thus less restrictive than the previous example. Taking into account the first free excursion distance of the electrodes 10 'and 11' enabled by the arrangement of the stops 24 and 25. The distance D m in between the two electrodes 10 'and 11' in the first direction A, shown here between the tooth 101 'of the comb electrode 10' and the tooth 102 'of the comb electrode 11', must be greater than DB. It is optionally possible, similar to the variants presented above, consider the risk of micro-arcing between the electrodes, in which case it can take a minimum distance D m i nin the unloaded state between the electrodes 10 'and 11' greater than the sum of the first distance DB of free excursion of the electrodes, and a distance D 2 in below which it is estimated that the risk of micro -arcage exists. In this case, the minimum distance D m j n between the electrode ends in the unloaded state is made greater than the sum DB + D2.

In addition, the electrodes 10 'and 11' being, again, movable with respect to each other not only in the first direction A, but also in the second direction B, the relative positioning of the two stop elements 24 and 25 according to this second direction B is also the subject of a criterion additional sizing.

If there is again OB 'the second distance of free excursion between the two abutment elements 24 and 25 according to this second direction B, the stack is arranged such that in the unloaded state, the first electrode 10' is at a distance Dmin 'to the second electrode 11' in the second direction B which is greater than this second free excursion distance DB.

Therefore it retains the second design criterion D m in '> DB' of the second embodiment.

It should be noted that although the illustrative examples described herein give see a layer comprising the electrodes, carrying the expected electromechanical system functionality, stacked on top of the layer comprising a stop member to prevent physical contact of the electrodes, a another arrangement wherein the layer comprising the electrodes is below the layer comprising the stop elements can be considered.

CLAIMS

1. A MEMS or sensor or actuator type NEMS, with a stop stack comprising:

- a first planar layer (1) comprising a first planar electrode (10) to be at a first electrical potential and a second planar electrode (1 1) intended to be to a second separate electrical potential of the first potential,

the first planar electrode (10) being movable relative to the second planar electrode (11) in a first direction (A) parallel to the first planar layer,

- a second planar layer (2) superimposed on the first planar layer (1), electrically insulated from the first planar layer (1) by at least one intermediate layer (3) formed of insulating material, the second planar layer (2) comprising a first planar member (20) mechanically integral with the first planar electrode (10) and a second planar member (21) mechanically secured to the second planar electrode (1 1),

characterized in that it further comprises at least one stop member (24) extending from the first planar member (20) or the second planar member (21) in the first direction (A) and projecting with respect to said plane in the first direction (A),

the stop element (24) extending from one of the planar elements being intended to be at the same potential as a facing surface (23) belonging to the other flat elements (21),

the stop element (24) and the electrodes being configured so that the stop element (24) comes into contact with the facing surface (23) and blocks the approximation of two planar electrodes (10, 11) according to first direction (a) during a solicitation.

2. MEMS or NEMS device according to claim 1, wherein the stop element and the electrodes are configured such that in the unloaded state, the entire free end (101) of the first planar electrode (10) is , with respect to a closest to the second electrode plate end (102) in the first direction (a) at a minimum distance (D m i n ) greater than a first free excursion distance (DB), said distance being defined as the minimum distance between the stop element (24) and the facing surface.

3. MEMS or NEMS device according to claim 2, wherein the minimum distance (D mi n) is greater than the sum of the first free excursion distance (DB) and a second predetermined distance, in below which there is a risk of loss of the insulating nature of the surrounding gas electrodes (10, 11) so that a short circuit may be established between two ends of the electrodes (101, 102).

4. MEMS or NEMS device according to any one of claims 1 to 3, wherein at least a first flat electrode (1 1 ') is at least partially deformable in the first direction (A), the sum of the maximum possible deformation according the first direction (a) of the electrodes (10 ', 1 1') defining a distance electrode arrow (DFE), the minimum distance (Dmin) is taken greater than the sum of the first free excursion distance (DB ) and the electrode distance of arrow (DFE).

5. MEMS or NEMS device according to any one of claims 1 to 4, wherein at least a first planar member (20) is at least partially deformable in the first direction (A), the sum of the maximum possible deformation in the first direction (a) of the planar members (20, 21) defining a distance of planar element arrow (D F p) given, the minimum distance (D m i n ) is taken greater than the sum of the first excursion distance free (DB) and the distance of planar element arrow (DFP).

6. MEMS or NEMS device according to claim 5, wherein at least one of the two planar elements (20, 21) is partially deformable in the first direction (A),

the second planar layer (2) being pierced with a cavity (26) formed in the anchoring of the abutment member (24) and / or being pierced with a cavity (27) formed along one edge the external surface (23) facing the stop element (24), the deflection distance (DFP) of planar member being defined as the sum of dimensions along the first direction (A) of the two cavities (26, 27) or, where applicable, defined as the dimension in the first direction of the single cavity, practiced (s) in the second planar layer (2).

7. MEMS or NEMS device according to Claim 4 and Claim 5 taken in combination, wherein the two planar electrodes (10 ', 1 1') and the two planar elements (20, 21) are deformable in the first direction (A ), the first planar member (21) carrying a first stop element (25) and the second planar member (20) carrying a second stop member (24),

a first opening cavity (13) being formed over the entire height of the stack to the anchoring of the first stop member (25) and corresponding in the first direction (A) with said first stop member (25), but not in correspondence in the first direction (a) with the second stop member (24), forming a first flexible leaf (14),

a second opening cavity (12) being formed over the entire height of the stack to anchor the second stop element (24) and corresponding in the first direction (A) with said second stop member (24), but not in correspondence in the first direction (a) with the first stop member (25) forming a second flexible blade (15), the first free excursion distance (D B ) being defined as the minimum distance between the first stop element (25) and the facing surface, the distance of electrode arrow (DFE) being defined as the sum of dimensions along the first direction (A) of the two emergent cavities (12, 13).

8. MEMS or NEMS device according to Claim 4 and Claim 5 taken in combination, wherein the first planar member (21) carries a first stop member (25) 'and the second planar member (20) carries a second element stop (24),

and wherein a first opening cavity (13 ') is formed over the entire height of the stack in the first planar electrode (1 1') in correspondence in the first direction (A) with one end (22 ') of the second stop element (24) facing each other, forming a first flexible leaf (15 '),

and a second outwardly opening cavity (13 ") is formed over the entire height of the stack in the first planar electrode (1 1 '), anchoring the first

stop element (25) in the first direction (A), and correspondingly in the first direction (A) with said first stop member (25) forming a second flexible blade (15 "),

the first free excursion distance (DB) is defined as the minimum distance between the first stop member (25) and the facing surface.

9. MEMS or NEMS device according to one of claims 1 to 8, wherein the two planar electrodes are further movable with respect to each other along a second direction (B) substantially perpendicular to the first direction (A )

the second direction (B) being parallel to the planar layer (1) containing the electrodes,

and wherein the first planar member (21) carries a first stop member (25) and the second planar member (20) carries a second stop member (24), the stack being configured such that in the state unsolicited, any free end of the first planar electrode (11 ') is located, relative to the second planar electrode (10') in the second direction (B) at a minimum distance (Dmm ') greater than a second distance free excursion (DB), the second free excursion distance (DB ') being defined as the minimum distance between the first and second stop elements (24, 25) along the second direction (B).

10. MEMS or NEMS device according to any one of the preceding claims, wherein one electrode comprises a flat plate and / or one electrode comprises an electrostatic comb.