MEMS inertial sensors with high resistance to static friction

Abstract

A MEMS inertial sensor with high resistance to static friction is disclosed. The MEMS inertial sensor includes a support structure and an inertial structure. The inertial structure includes at least one inertial mass, an elastic structure, and a stop structure. The elastic structure is mechanically coupled to the inertial mass and the support structure so that when the support structure is subjected to an acceleration parallel to a first direction, the inertial mass can move in a direction parallel to the first direction. The stop structure is fixed relative to the support structure and includes at least one primary stop element and one secondary stop element. If the acceleration exceeds a first threshold, the inertial mass abuts the primary stop element and subsequently rotates about a rotation axis defined by the primary stop element. If the acceleration exceeds a second threshold, the rotation of the inertial mass is terminated when the inertial mass abuts the secondary stop element.

Description

Technical Field

[0001] The present disclosure relates to a MEMS (Micro Electro Mechanical System) inertial sensor that is highly resilient to stiction phenomena. Background Art

[0002] As is known, MEMS inertial sensors include, for example, MEMS type accelerometers, which in turn include a suspended inertial mass located in a main extension plane. Typically, due to the action of external acceleration, the inertial mass is supported to move in a direction parallel to the main extension plane (sensing axis).

[0003] For example, Figure 1A and Figure 1B A known capacitive MEMS accelerometer 1 is shown under two different operating conditions. Figure 1A and Figure 1B A Cartesian reference system XYZ is shown, whose plane XY coincides with the aforementioned main extension plane.

[0004] The MEMS accelerometer 1 comprises an inertial mass 3 of semiconductor material (eg silicon) having a planar shape and Figure 1A and Figure 1B For example, the inertial mass 3 has a quadrilateral (e.g., rectangular) frame shape in top view and has a through-type opening 9. In other words, the inertial mass 3 has a parallelepiped shape on the outside; furthermore, the opening 9 also has a parallelepiped shape.

[0005] The first electrode 13 and the second electrode 15, both made of a semiconductor material (e.g., silicon), extend in the opening 9 and are anchored to the underlying substrate by means of respective anchor portions 13A, 15A. In particular, the first electrode 13 and the second electrode 15 have an elongated quadrilateral (e.g., rectangular) shape in top view, extending primarily along the axis X.

[0006] In particular, the inertial mass 3 has first and second inner surfaces 3A, 3B which laterally delimit the opening 9 and respectively face the first and second electrodes 13, 15. The first and second inner surfaces 3A, 3B are planar and extend in a direction parallel to the plane XZ.

[0007] The MEMS accelerometer 1 has a sensing axis S parallel to the axis Y. Furthermore, the inertial mass 3 has a center of mass O which is arranged at point d0 in the rest state.

[0008] In more detail, in the static state of the MEMS accelerometer 1, the first inner surface 3A and the second inner surface 3B are respectively arranged at a first distance d1 and a second distance d2 from the first electrode 13 and the second electrode 15. In the static state of the MEMS accelerometer 1, the first surface 3A and the second surface 3B and the first electrode 13 and the second electrode 15 are capacitively coupled to each other and form plates of corresponding capacitors with capacitances C1 and C2.

[0009] The inertial mass 3 is traversed throughout its thickness (in a direction parallel to the axis Z) by a plurality of holes 17 which enable the inertial mass 3 to be released during the manufacturing process.

[0010] The inertial mass 3 is coupled to a constraint element 5, which is fixed relative to the substrate, by means of a spring element 7, which is configured to respond to an external acceleration a having a component directed parallel to the axis Y. ext , causing the inertial mass 3 to be displaced (in particular translated) along the sensing axis S. In the example of embodiment shown, the constraining element 5 is arranged outside the inertial mass 3 and is coupled to the above-mentioned frame-shaped first outer wall 3C of the inertial mass 3 .

[0011] The MEMS accelerometer 1 further comprises a stop element 19, formed for example by a fixing area extending from the base at a distance from the inertial mass 3. In particular, in the example of embodiment shown, the stop element 19 is arranged outside the inertial mass 3 and facing a second outer wall 3D of the inertial mass 3, which is opposite the first outer wall 3C, at a distance. Figure 1A In the static state of the MEMS accelerometer 1 shown in FIG, the stop element 19 is arranged at a stop distance d from the second outer wall 3D of the inertial mass 3. s Place.

[0012] In use, the inertial mass 3 and the first and second electrodes 13 and 15 are biased to respective bias voltages. For example, there is a voltage of approximately 1V between the inertial mass 3 and each of the first and second electrodes 13 and 15.

[0013] Due to the bias, the inertial mass 3 is subjected to a total electrostatic force F el , total electrostatic force F el By the first electrostatic force F el1 and the second electrostatic force F el2 In particular, the first electrostatic force F el1 Acting between the first electrode 13 and the first inner surface 3A, the second electrostatic force F el2 Acts between the second electrode 15 and the second inner surface 3B.

[0014] The MEMS accelerometer 1 is designed such that in a stationary state, the first distance d1 and the second distance d2 between the inertial mass 3 and the first electrode 13 and the second electrode 15 are the same, and the first capacitance C1 and the second capacitance C2 are also the same. el1 and the second electrostatic force F el2 are the same, and the total electrostatic force F el Therefore, in the static state, the spring element 7 is not deformed.

[0015] In use, assuming that the external acceleration a acting on the MEMS accelerometer 1 ext Oriented along the sensing axis S (e.g., downward in the plane of the drawing), the inertial mass 3 is in contact with the external acceleration a ext The translation occurs along the sensing axis S in the opposite direction, such as Figure 1B As shown in . Therefore, the distances d1, d2 (and therefore the capacitances C1, C2) change. In particular, the first distance d1 decreases, while the second distance d2 increases; furthermore, the first capacitance C1 increases, while the second capacitance C2 decreases. These changes in capacitance represent the external acceleration a ext The value of the external acceleration a is measured by detecting the changes in the capacitances C1 and C2. ext For example, the MEMS accelerometer 1 may be coupled to an ASIC (Application Specific Integrated Circuit), which provides a corresponding reading interface and is configured to generate a signal corresponding to the external acceleration a according to the values ​​of the first capacitor C1 and the second capacitor C2. ext proportional signal.

[0016] When the inertial mass block 3 passes a distance equal to the stopping distance d s The translation of the inertial mass 3 is interrupted when it abuts against the stop element 19 after a distance of . T , the position is translated relative to point d0 in a direction parallel to the sensing axis S by a distance equal to the stopping distance d s Therefore, the distance between the first electrode 13 and the first inner surface 3A is equal to d1-d s , and the distance between the second electrode 15 and the second inner surface 3B is equal to d2+d s .

[0017] Specifically, when the inertial mass 3 abuts against the stop element 19, it is subjected to a total electrostatic force F given by formula (1): el :

[0018]

[0019] Where ε is the dielectric constant, A elis the area of ​​the first electrode 13 and the second electrode 15 (and therefore also the area of ​​the portion of the surface 3A, 3B of the inertial mass 3 facing them), and ΔV is the voltage between the plates of the capacitors C1 , C2 .

[0020] In addition, when the inertial mass 3 abuts against the stop element 19, the stiction force F a Acting on it, the static friction force F a The tendency is to bring it into abutment against the stop element 19 .

[0021] Once the external acceleration a ext Termination (i.e., a ext =0), the elastic restoring force F exerted by the spring element 7 m Tends to make the inertial mass 3 return to Figure 1A The rest position shown in FIG, in particular, the elastic restoring force F m It acts along the sensing axis S in a direction opposite to the displacement direction of the inertial mass 3 .

[0022] Elastic recovery force F m Given by formula (2):

[0023] F m =-k·d s (2)

[0024] In order to overcome the static friction F a And return the inertial mass 3 to the rest position so that further acceleration can be detected, the spring element 7 is designed so that the elastic restoring force F m Able to compensate for static friction F a and Figure 1B The total electrostatic force F is set in the steps shown in el In other words, we hope

[0025] F m >α(F el +F a(t＝0) ) (3)

[0026] Among them F a(t＝0) is the inherent static friction (ie, the static friction estimated before the MEMS accelerometer 1 is used for the first time), and α is a safety factor.

[0027] However, the static friction force F a The estimation and compensation of the static friction force F is complex. a It depends on several tribological aspects associated with geometry, material, manufacturing process and operating conditions and is variable in time.

[0028] Furthermore, the safety factor α in formula (3) cannot be set arbitrarily, but must be considered in consideration of the trade-off between the required performance and the manufacturing cost. In fact, it depends on the structure and electromechanical parameters of the MEMS accelerometer 1 (such as the constant k of the spring element 7, the stopping distance d between the second outer wall 3D of the inertial mass 3 and the stopping element 19). s and the area A of electrodes 13 and 15 el ). However, current structural requirements (such as bandwidth, packaging, noise and full-scale requirements) do not allow for free selection of the above structural parameters, so it is not always possible to maximize the safety factor α. In particular, the stop distance d s It is subject to constraints resulting from the need to have a linear response of the MEMS accelerometer 1 and from the shape and arrangement of the opening 9 and the first 13 and second 15 electrodes. Summary of the Invention

[0029] In various embodiments, the present disclosure provides a MEMS inertial sensor that will at least

[0030] Partially overcome the shortcomings of the existing technology.

[0031] According to one or more embodiments of the present disclosure, a MEMS inertial sensor is provided, comprising a support structure, an inertial structure including at least one first inertial mass, a first resilient structure, and a first stopper structure. The first resilient structure is mechanically coupled to the first inertial mass and the support structure such that, when the support structure is subjected to a first acceleration parallel to the first direction, the first inertial mass can move relative to the support structure in a direction parallel to the first direction. The first stopper structure is fixed relative to the support structure and comprises at least one first primary first-axis stop element and a secondary first-axis stop element. The first primary first-axis stop element is configured such that, if the first acceleration exceeds a first threshold, the first inertial mass abuts the first primary first-axis stop element and subsequently rotates about a first rotational axis defined by the first primary first-axis stop element. The secondary first-axis stop element is configured such that, if the first acceleration exceeds a second threshold that is higher than the first threshold, rotation of the first inertial mass is terminated when the first inertial mass abuts the secondary first-axis stop element.

[0032] In at least one embodiment, a MEMS inertial sensor is provided, comprising a support structure, an inertial structure including at least one first inertial mass, a first elastic structure, a second elastic structure, and a first stopper structure. The first elastic structure is mechanically coupled to the first inertial mass and the support structure such that, when the support structure is subjected to a first acceleration parallel to the first direction, the first inertial mass can move relative to the support structure in a direction parallel to the first direction. The second elastic structure is elastically coupled to the second inertial mass and the support structure and configured such that, when the support structure is subjected to a second acceleration parallel to the second direction, the second inertial mass can move relative to the support structure in a direction parallel to the second direction. A main axis electrode is fixed relative to the support structure and capacitively coupled to the first inertial mass to form a corresponding main axis capacitor, the capacitance of the main axis capacitor being indicative of the first acceleration. A transverse axis electrode is fixed relative to the support structure and capacitively coupled to the second inertial mass to form a corresponding transverse axis capacitor, the capacitance of the transverse axis capacitor being indicative of the second acceleration. A first stopper structure is fixed relative to the support structure and comprises at least one first main first axis stop element and a second secondary first axis stop element.

[0033] In at least one embodiment, an electronic device is provided that includes a MEMS inertial sensor, an ASIC coupled to the MEMS inertial sensor, and a processing unit coupled to the ASIC. The MEMS inertial sensor includes a support structure, an inertial structure including at least one first inertial mass, a first resilient structure, and a first stopper structure. The first resilient structure is mechanically coupled to the first inertial mass and the support structure such that, when the support structure is subjected to a first acceleration parallel to the first direction, the first inertial mass can move relative to the support structure in a direction parallel to the first direction. The first stopper structure is fixed relative to the support structure and includes at least one first primary first-axis stop element and a secondary first-axis stop element. The first primary first-axis stop element is configured such that, if the first acceleration exceeds a first threshold, the first inertial mass abuts the first primary first-axis stop element and subsequently rotates about a first rotational axis defined by the first primary first-axis stop element. The secondary first-axis stop element is configured such that, if the first acceleration exceeds a second threshold that is higher than the first threshold, rotation of the first inertial mass is terminated when the first inertial mass abuts the secondary first-axis stop element. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] For a better understanding of the present disclosure, embodiments thereof will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0035] Figure 1A and Figure 1BSchematic diagrams of top views of a known type of MEMS inertial sensor in a static position and in the presence of external acceleration, respectively;

[0036] Figure 2 is a top view schematic diagram of the MEMS inertial sensor in a stationary state;

[0037] Figures 3 to 5 When the MEMS inertial sensor is subjected to external acceleration, Figure 2 Schematic diagram of a top view of the MEMS inertial sensor at successive moments shown in FIG;

[0038] Figure 6 is a top view schematic diagram of another embodiment of the MEMS inertial sensor in a stationary state;

[0039] Figure 7 Shown Figure 6 an enlarged view of a portion of;

[0040] Figure 8 and Figure 9 yes Figures 6 and 7 A schematic top view of the embodiment shown in FIG when subjected to a first acceleration;

[0041] Figure 10 and 11 yes Figures 6 and 7 A schematic top view of the embodiment shown in FIG when subjected to a second acceleration; and

[0042] Figure 12 A block diagram of an electronic device incorporating a MEMS inertial sensor is shown. DETAILED DESCRIPTION

[0043] Figure 2 A MEMS inertial sensor, specifically a capacitive MEMS accelerometer 30, is shown. Figure 1A and Figure 1B Components already present in the MEMS accelerometer 1 will be designated by the same reference symbols unless otherwise specified.

[0044] In place of the stop element 19, the MEMS accelerometer 30 includes a first stop structure 109, which includes a primary stop element 110 and a first (secondary) stop element 119A and a second stop element 119B, wherein the first stop element 119A and the second stop element 119B are made of a semiconductor material and are formed as a whole with an underlying substrate (not shown).

[0045] In a first approximation, in top view, the main stop element 110 is wedge-shaped with its apex directed towards the second outer wall 3D of the inertial mass 3. In particular, the main stop element 110 is defined by an apex edge 110V parallel to the axis Z and situated in a plane parallel to the plane ZY containing the sensing axis S, hereinafter called the symmetry plane SP.

[0046] In a stationary condition, the vertex edge 110V is parallel to the second outer wall 3D of the inertial mass 3, and the distance between it and the second outer wall 3D of the inertial mass 3 is equal to the first stopping distance d s1 , which is smaller than the first distance d1 and the second distance d2 mentioned above, and exists between the inertial mass block 3 and the first electrode 13 and the second electrode 15 respectively under static conditions.

[0047] Without any loss of generality, the first and second stop elements 119A, 119B have the same shape as one another and are symmetrical with respect to the symmetry plane SP. For example, each of the first and second stop elements 119A, 119B is L-shaped in top view, with the concave surface facing the second outer wall 3D of the inertial mass 3.

[0048] In more detail, each L-shaped portion of the first and second stop elements 119A, 119B comprises a corresponding portion having a parallelepiped shape extending in a direction parallel to the second outer wall 3D of the inertial mass 3 and consisting of a corresponding side wall (respectively, in the case of the first stop element 119A, P A designated, and in the case of the second stop element 119B by P B Designated), which faces the corresponding portion of the second outer wall 3D of the inertial mass 3 and is parallel to the plane ZX. In the static state, the side walls P of the first stop element 119A and the second stop element 119B A 、P B By being greater than the first stopping distance d s1 The second stopping distance d s2 Separated from the second outer wall 3D of the inertial mass 3 .

[0049] Similar to the MEMS accelerometer 1 already mentioned, the MEMS accelerometer 30 is also designed to detect external accelerations parallel to the sensing axis S, and therefore parallel to the Y axis.

[0050] In use, it is assumed that Figure 1B The same external acceleration a ext , so for simplicity, assume that the external acceleration a ext Without any component along X or along Z, the following happens.

[0051] Inertial mass block 3 is subjected to external acceleration a ext The inertial mass 3 is translated in the opposite direction parallel to the sensing axis S, and therefore in the direction of the first stop structure 109. When the inertial mass 3 abuts (i.e. strikes) against the vertex edge 110V of the main stop element 110 (e.g. Figure 3 ), that is, the inertial mass 3 experiences a displacement along the sensing axis S equal to the first stopping distance d s1 After that, the translation stops. Before this moment, the operation of the MEMS accelerometer 30 is similar to Figure 1A and Figure 1B The operation of the MEMS accelerometer 1 is shown in FIG.

[0052] When the inertial mass 3 strikes the vertex edge 110V, the spring element 7 undergoes a first deformation. In addition, the inertial mass 3 is still away from the first stop element 119A and the second stop element 119B because, as mentioned above, the second stop distance d s2 Greater than the first stopping distance d s1 Under these conditions, Figure 1B The considerations also apply, except that the reference first stop distance d s1 Instead of the stopping distance d s .

[0053] After the inertial mass 3 hits the vertex edge 110V, assuming the external acceleration a ext If the above impact is not enough to stop the movement of the inertial mass 3, the following happens.

[0054] In detail, Figure 4 As shown in , the inertial mass 3 begins to rotate around an axis of rotation coinciding with the vertex edge 110V, which serves as an instantaneous center of rotation. Depending on the inevitable defects that change the symmetry of the system formed by the spring element 7, the inertial mass 3 and the vertex edge 110V, the rotation occurs in a clockwise or counterclockwise direction. Alternatively (case not shown), the spring element 7 can be configured so that it is not only able to translate along the sensing axis S of the inertial mass 3, but also simultaneously causes a simultaneous translation on the inertial mass 3 in a direction parallel to the axis Y, which is negligible with respect to the translation along the sensing axis S, but is sufficient to impose the direction of the subsequent rotation of the inertial mass 3. In addition, under an external acceleration a ext In the case of a non-zero component parallel to the axis X, this component is also consistent in determining the direction of rotation. In any case, the direction of rotation of the inertial mass 3 is irrelevant to the operating purpose of the MEMS accelerometer 30. For example only, in Figure 4 The rotation is assumed to occur in a clockwise direction.

[0055] If the external acceleration a extHigh enough, the rotation of the inertial mass 3 will not stop until the inertial mass 3 abuts against the side wall PB of the secondary stop element 119B, as shown in FIG. Figure 5 Under these conditions, the spring element 7 undergoes a second deformation different from the aforementioned first deformation. If it is rotated in the counterclockwise direction, on the contrary, the inertial mass 3 will abut against the side wall P of the first stop element 119A. A stop.

[0056] In more detail, and without any loss of generality, the side wall P of the secondary stop element 119B B Contact occurs between the side EX (parallel to the axis Z) of the second outer wall 3D of the outer mass 3. Furthermore, the shape and mutual arrangement of the opening 9 and of the first and second electrodes 13, 15 are such that, during translation and subsequent rotation, the inertial mass 3 remains at a distance from the first and second electrodes 13, 15; i.e., the inertial mass 3 does not strike the first and second electrodes 13, 15.

[0057] In fact, the arrangement of the main stop element 110, more precisely the first stop distance d s1 , determines the full-scale value; that is, it determines the external acceleration a parallel to the axis Y that can be correctly detected by the MEMS accelerometer 30 ext In this regard, as mentioned before, the external acceleration a ext The measurement can be compared with the reference Figure 1A and Figure 1B Proceed in the same manner as described above.

[0058] The external acceleration a parallel to the Y axis ext When the value of the component exceeds the full-scale value, the rotation of the inertial mass 3 occurs near the vertex edge 110V.

[0059] The arrangement of the first stop element 119A and the second stop element 119B, more precisely, the second stop distance d s2 , determines the maximum deformation to which the spring element 7 may be subjected and, therefore, the external acceleration a parallel to the axis Y before the protection provided by the first stop element 119A and the second stop element 119B intervenes. ext Furthermore, given the same full scale, the above deformation makes Figure 5 Under the conditions indicated in , the elastic potential energy stored by the spring element 7 is greater than the energy it would store in the absence of the primary stop element 110. In the latter case, the movement of the inertial mass 3 will stop, and the second outer wall 3D of the inertial mass 3 will abut against the side walls P of the primary stop element 119A and the secondary stop element 119B. A 、P B .

[0060] Therefore, when the external acceleration a ext At the end, the elastic restoring force F m Therefore, the probability of stiction phenomena occurring between the inertial mass 3 and the first stop structure 109 decreases, and thus the probability that the inertial mass 3 cannot return to the position occupied in the rest state decreases.

[0061] Furthermore, referring to the limit value to indicate the minimum value of the component of the external acceleration aext parallel to the axis Y, the inertial mass 3 is brought into contact with one of the first stop element 119A and the second stop element 119B, and the following occurs. ext For values ​​of the component of which the value is above the full-scale value but below the limit value, the likelihood of stiction is reduced, since the contact surface between the inertial mass 3 and the main stop element 110 is greatly reduced (to a first approximation, given only by the vertex edge 110V) and since the inertial mass 3 rotates, this leads to an increase in the elastic potential energy stored by the spring element 7 and, therefore, an increase in the elastic restoring force.

[0062] Figure 6 Another embodiment is shown. In particular, Figure 6 A MEMS accelerometer 100 is shown having two sensing axes.

[0063] Specifically, the MEMS accelerometer 100 includes a first inertial mass block 103 and a second inertial mass block 104, wherein the first inertial mass block 103 and the second inertial mass block 104 have a planar structure with a major dimension parallel to the plane XY and a negligible thickness along the axis Z. Figure 6 The substrate and the first and second inertial masses 103 and 104 are made of semiconductor materials (eg, silicon).

[0064] The first inertial mass 103 laterally delimits a main opening 139, within which the second inertial mass 104 extends, so that the second inertial mass 104 is laterally surrounded by the first inertial mass 103. Without implying any loss of generality, in top view, the main opening 139 has a symmetrical shape with respect to a first symmetry plane SP1 parallel to the plane XZ and with respect to a second symmetry plane SP2 parallel to the plane ZY.

[0065] The second inertial mass 104 occupies an outer portion of the main opening 139 and laterally defines a first secondary opening 120 and a second secondary opening 121 which are part of the main opening 139 and have, in top view, a shape identical and symmetrical to the second symmetry plane SP2 .

[0066] More specifically, the second inertial mass 104 includes a corresponding central body 105 that transversely defines a first opening 120 and a second opening 121, as well as a first vertical arm 122 and a second vertical arm 124, each having a parallelepiped shape and extending in a direction parallel to the axis Y. Furthermore, the first vertical arm 122 and the second vertical arm 124 are identical to each other and symmetrical with respect to the first plane of symmetry SP1, and extend on opposite sides of the central body 105, forming a single unitary body with the central body 105. Specifically, the first vertical arm 122 and the second vertical arm 124 extend from the central body 105 toward the first inertial mass 103. More specifically, each of the first vertical arm 122 and the second vertical arm 124 has a proximal end fixed to the central body 105 and a distal end, which will be discussed below.

[0067] MEMS accelerometer 100 also includes a first anchor region 125 and a second anchor region 126, which extend within first and second openings 120, 121, respectively, and are secured to the underlying substrate, forming a single unitary structure therewith. Thus, first and second anchor regions 125, 126 are formed of a semiconductor material and have identical shapes (e.g., parallelepipeds elongated in a direction parallel to axis X) that are symmetrical with respect to second symmetry plane SP2. Furthermore, reference is made to central region 105* to indicate the portion of central body 105 interposed between first and second openings 120, 121. Each of first and second anchor regions 125, 126 has a first end oriented toward central region 105* and a second end oriented in an opposite direction, as described in greater detail below. The proximal ends of first and second vertical arms 122, 124 are secured to central region 105* of central body 105.

[0068] MEMS accelerometer 100 further includes a first horizontal arm 132 and a second horizontal arm 134. The first horizontal arm 132 and the second horizontal arm 134 are parallelepiped-shaped, extending in a direction parallel to axis X, extending over the substrate at a predetermined distance, and being identical to each other and symmetrical with respect to a second symmetry plane SP2. Furthermore, the first horizontal arm 132 and the second horizontal arm 134 extend within the first and second openings 120 and 121, respectively.

[0069] More specifically, first horizontal arm 132 and second horizontal arm 134 are formed of a semiconductor material and are integrally formed with first anchor region 125 and second anchor region 126, respectively. More specifically, each of first horizontal arm 132 and second horizontal arm 134 has a first end and a second end. The first ends of first horizontal arm 132 and second horizontal arm 134 are fixed to the second ends of first anchor region 125 and second anchor region 126, respectively.

[0070] The MEMS accelerometer 100 further includes a first spring element 142 and a second spring element 144, which are folded, serpentine-shaped in top view, and compliant in a direction parallel to the axis X. Furthermore, the first spring element 142 and the second spring element 144 have negligible thickness in a direction parallel to the axis Z. Furthermore, the first spring element 142 and the second spring element 144 are identical to each other and symmetrical with respect to the second symmetry plane SP2.

[0071] In detail, the first spring element 142 and the second spring element 144 extend in the first opening 120 and the second opening 121 respectively, so that the first horizontal arm 132 is inserted between the first anchoring area 125 and the first spring element 142, and the second horizontal arm 134 is inserted between the second fixing area 126 and the second spring element 144.

[0072] In more detail, the first spring element 142 has a first end and a second end, each of which is fixed to the second end of the first horizontal arm 132 and a first point of the second inertial mass 104, respectively. The second spring element 144 has a corresponding first end and a corresponding second end, each of which is fixed to the second end of the second horizontal arm 134 and a second point of the second inertial mass 104, respectively. The first and second points of the second inertial mass 104 are symmetrical with respect to the second symmetry plane SP2. Furthermore, the first and second points of the second inertial mass 104 are aligned along the direction in which the first and second horizontal arms 132 and 134 extend.

[0073] The MEMS accelerometer 100 further includes a third spring element 152 and a fourth spring element 154, which are folded, have a serpentine shape in top view, and are compliant in a direction parallel to the axis Y. Furthermore, the third spring element 152 and the fourth spring element 154 have negligible thickness in a direction parallel to the axis Z. Furthermore, the third spring element 152 and the fourth spring element 154 are identical to each other and symmetrical with respect to the first symmetry plane SP1.

[0074] In detail, the third spring element 152 and the fourth spring element 154 are arranged in the main opening 139 between the first inertial mass 103 and the second inertial mass 104 .

[0075] In more detail, the third spring element 152 has a first end and a second end, respectively fixed to the distal end of the first vertical arm 122 and a first point of the first inertial mass 103. The fourth spring element 154 has a first end and a second end, respectively fixed to the distal end of the second vertical arm 124 and a second point of the first inertial mass 103. The first and second points of the first inertial mass 103 are symmetrical with respect to the first symmetry plane SP1; furthermore, the first and second points of the first inertial mass 103 are aligned in the direction of elongation of the first and second vertical arms 122, 124.

[0076] In more detail, the first inertial mass 103 has the shape of a parallelepiped on the outside, except for the presence of first and second central recesses RC1 and RC2 and first, second, third and fourth angular recesses RA1, RA2, RA3 and RA4.

[0077] The first central recess RC1 and the second central recess RC2 have the same parallelepiped shape and are symmetrical with respect to the first symmetry plane SP1, and are also aligned along the extension direction of the first vertical arm 122 and the second vertical arm 124. In addition, the first central recess RC1 and the second central recess RC2 are laterally delimited by the first outer side wall P1 and the second outer side wall P2, respectively, and the first outer side wall P1 and the second outer side wall P2 are parallel to the plane ZX in the static state.

[0078] The first angular recess RA1 , the second angular recess RA2 , the third angular recess RA3 and the fourth angular recess RA4 form respective indentations arranged along the sides of the first inertial mass 103 .

[0079] Specifically, each of the first, second, third, and fourth angular recesses RA1, RA2, RA3, and RA4 is defined by a corresponding pair of walls, the walls comprising: a corresponding horizontal peripheral wall, which is parallel to the plane XZ in a resting state and is designated by the same reference symbol with a prime symbol added thereto; and a corresponding vertical peripheral wall, which is parallel to the plane YZ in a resting state and is designated by the same reference symbol with a second prime symbol added thereto. In each of the first, second, third, and fourth angular recesses RA1, RA2, RA3, and RA4, the corresponding horizontal peripheral wall and the corresponding vertical peripheral wall are connected to each other at a right angle.

[0080] The MEMS accelerometer 100 further includes a first external main stop element 162 and a second external main stop element 164, as well as a first stop element 170, a second stop element 172, a third stop element 174 and a fourth stop element 176, which are made of semiconductor material, extend outside the first inertial mass block 103, and are fixed to the underlying substrate to form an integral unit.

[0081] Each of the first external main stop element 162 and the second external main stop element 164 and the first stop element 170, the second stop element 172, the third stop element 174 and the fourth stop element 176 has a corresponding body (designated by a corresponding reference symbol with an added angular symbol), for example, they have the shape of a parallelepiped and their bottom is fixed to the base.

[0082] The first outer main stop element 162 and the second outer main stop element 164 are identical to each other and symmetrical with respect to the first symmetry plane SP1. In addition, each of the first outer main stop element 162 and the second outer main stop element 164 includes a corresponding protruding area (designated by the corresponding reference symbol with the letter V added) that is separated from the corresponding body and faces the first inertial mass 103.

[0083] The bodies 162′, 164′ of the first and second outer main stop elements 162, 164 extend at least partially within the first and second central recesses RC1, RC2, respectively. The protruding areas 162V, 164V of the first and second outer main stop elements 162, 164, respectively, extend within the first and second central recesses RC1, RC2, such that the protruding areas 162V of the first outer main stop element 162 extend between the corresponding bodies 162′ and the first inertial mass 103, while the protruding areas 164V of the second outer main stop element 164 extend between the corresponding bodies 164′ and the first inertial mass 103.

[0084] More specifically, the protruding area 162V of the first external main stop element 162 is fixed to the base at its bottom and extends from the main body 162' a distance toward the first outer sidewall P1 of the first central recess RC1 that it faces. Specifically, in a static state, the protruding area 162V of the first external main stop element 162 is separated from the first outer sidewall P1 by a distance dY1. The protruding area 164V of the second external main stop element 164 is fixed to the base at its bottom and extends from the main body 164' a distance toward the second outer sidewall P2 of the second central recess RC2 that it faces. To a first approximation, in a static state, the protruding area 164V of the second external main stop element 164 is separated from the second outer sidewall P2 by the aforementioned distance dY1.

[0085] Without any loss of generality, the protruding areas 162V, 164V of the first and second external main stop elements 162, 164 have a beveled shape approximately similar to a semi-cylinder having an axis parallel to the Z axis and having a diameter (in top view) that is in contact with the corresponding body 162', 164'.

[0086] The bodies 170', 162', 174', 176 of the first, second, third, and fourth stop elements 170, 172, 174, and 176 extend at least partially within the first, second, third, and fourth angular recesses RA1, RA2, RA3, and RA4, respectively. Furthermore, each of the first, second, third, and fourth stop elements 170, 172, 174, and 176 includes a corresponding first protruding area (designated by a corresponding reference numeral with the letter V added) and a corresponding second protruding area (designated by a corresponding reference numeral with the letter H added). The first protruding areas 170V to 176V and the second protruding areas 170H to 176H of the first, second, third, and fourth stop elements 170, 172, 174, and 176 extend within the first, second, third, and fourth angular recesses RA1, RA2, RA3, and RA4, respectively.

[0087] Without any loss of generality, the first and second protruding regions 170V to 176V, 170H to 176H each have a beveled shape approximating a semi-cylinder having an axis parallel to the Z axis and a diameter (in top view) in contact with the corresponding body 170' to 176'.

[0088] In more detail, the first protruding areas 170V, 172V, 174V, 176V start from the main bodies 170', 172', 174', 176 of the first stop element 170, the second stop element 172, the third stop element 174 and the fourth stop element 176, respectively, and extend along the horizontal peripheral walls RA', RA2', RA3', RA4' of the first corner groove RA1, the second corner groove RA2, the third corner groove RA3 and the fourth corner groove RA4, respectively, and in the static state, they are separated by the same distance dY2, which is greater than the distance dY1.

[0089] The second protruding areas 170H, 172H, 174H, 176H start from the main bodies 170', 172', 174', 176 of the first stop element 170, the second stop element 172, the third stop element 174 and the fourth stop element 176, respectively, and extend along the vertical peripheral walls RA", RA2", RA3", RA4" of the first corner groove RA1, the second corner groove RA2, the third corner groove RA3 and the fourth corner groove RA4, respectively. In the static state, they are separated by the same distance dX2.

[0090] Without any loss of generality, and to a first approximation, the first and second stop elements 170, 172 are identical to one another and are symmetrical with respect to the first plane of symmetry SP1, as are the third and fourth stop elements 174, 176. Furthermore, the first and fourth stop elements 170, 176 are identical to one another and are symmetrical with respect to the second plane of symmetry SP2, as are the second and third stop elements 172, 174.

[0091] like Figure 7 As shown in more detail in FIG, the MEMS accelerometer 100 further includes first and second internal main stop elements 180, 182 formed of a semiconductor material.

[0092] Specifically, as previously described, the central region 105* of the second inertial mass 104 extends between the first and second openings 120 and 121. Furthermore, the central region 105* is laterally bounded by a first wall PC1 and a second wall PC2 (hereinafter referred to as first and second inner walls PC1 and PC2). In a static state, the first and second inner walls PC1 and PC2 are parallel to the plane YZ and symmetrical with respect to the second plane of symmetry SP2.

[0093] As already mentioned, the first and second inner main stop members 180, 182 are secured to the underlying substrate. Furthermore, the first inner main stop member 180 extends transversely from the first end of the first anchoring region 125 along the first inner wall PC1. In a resting state, the first inner main stop member 180 is separated from the first inner wall PC1 by a distance dX1, which is less than the distance dX2. The second inner main stop member 182 extends transversely from the first end of the second anchoring region 126 along the second inner wall PC2. In a resting state, the second inner main stop member 182 is separated from the second inner wall PC2 by a distance dX1.

[0094] Without any loss of generality, the first 180 and second 182 inner main stop elements are identical to one another and symmetrical with respect to the second plane of symmetry SP2. Furthermore, the first 180 and second 182 inner main stop elements have a beveled shape, approximately similar to a semi-cylinder having an axis parallel to the axis Z and having a diameter (in top view) in contact with the corresponding body 125, 126.

[0095] Furthermore, there are a plurality of first additional openings 200 in the second inertial mass 104, which have the same shape as one another and pass through the central body 105 of the second inertial mass 104 so as to face the underlying substrate. Figure 7 In the embodiment shown, there are eight first additional openings 200, divided into two groups of four each, and having, for example, the shape of a parallelepiped elongated (in the rest state) in a direction parallel to the axis Y. The two groups have a symmetrical arrangement with respect to the second symmetry plane SP2; moreover, in each group, the corresponding four first additional openings 200 are arranged in two pairs, each pair comprising two first additional openings 200 aligned in a direction parallel to the axis X, the two pairs in the group being identical to each other and symmetrical with respect to the first symmetry plane SP1.

[0096] Furthermore, there are a plurality of second additional openings 202 in the first inertial mass 103, which have the same shape as one another and pass through the first inertial mass 103 so as to face the underlying substrate. Figure 7 In the embodiment shown, there are twelve second additional openings 202, divided into two groups of six each, and having, for example (in the static state) the shape of a parallelepiped elongated in a direction parallel to the axis X. The two groups have a symmetrical arrangement with respect to the first symmetry plane SP1; moreover, in each group, the corresponding six second additional openings 202 are arranged in pairs of three, wherein each pair includes three second additional openings 200 aligned in a direction parallel to the axis Y, the two triplets of the group being identical to each other and symmetrical with respect to the second symmetry plane SP2.

[0097] In each first additional opening 200 and each second additional opening 202 there is a corresponding first electrode (designated by 213 in the case of the first additional opening 200 and by 223 in the case of the second additional opening 202, respectively) and a corresponding second electrode (designated by 215 in the case of the first additional opening 200 and by 225 in the case of the first additional opening 202, respectively) which are formed of a semiconductor material (e.g., silicon) and anchored to the underlying substrate.

[0098] In addition, in each first additional opening 200, the corresponding first electrode 213 and the corresponding second electrode 215 are arranged in a manner similar to the reference electrode. Figures 1A to 5In a similar manner to that described in the previous embodiment, a first variable capacitor C having a first inner surface 200A and a second inner surface 200B of the first additional opening 200 is formed. X1 and the second variable capacitor C X2 In a static state, the first inner surface 200A and the second inner surface 200B are parallel to the plane ZY.

[0099] Likewise, in each second additional opening 202, the corresponding first electrode 223 and the corresponding second electrode 225 are aligned with the reference electrode 224. Figures 1A to 5 In a similar manner to that described in the previous section, the first inner surface 202A and the second inner surface 202B having the second additional opening 202 are formed to form the corresponding first variable capacitor C. Y1 and the corresponding second variable capacitor C Y2 In a static condition, the first inner surface 202A and the second inner surface 202B are parallel to the plane ZX.

[0100] In use, it is assumed that the substrate is subjected to an external acceleration a ext Parallel to axis X and in the same direction Figure 6 If the direction of the axis X shown is opposite, the following occurs.

[0101] The second inertial mass block 104 and the first inertial mass block 103 move together to the right (at Figure 6 In the plane of the axis X), since the third spring element 152 and the fourth spring element 154 are rigid in a direction parallel to the axis X, the first spring element 142 and the second spring element 144 are deformed accordingly, the first spring element 142 is extended, and the second spring element 144 is compressed.

[0102] Assume that the external acceleration a ext If the modulus of is high enough (ie exceeds a first threshold), the translation continues until the first inner wall PC1 of the second inertial mass 104 abuts against the first inner main stop element 180, as shown in FIG. Figure 8 As shown in .

[0103] The first inner main stop element 180 serves as a rotation center of the whole formed by the first and second inertial masses 103 and the third and fourth spring elements 152 and 154, which rotate in a fixed manner relative to each other. Figure 4 Related considerations apply; for example, in the following, it is assumed that the rotation occurs in the clockwise direction. In addition, if the external acceleration a ext If the modulus of exceeds a second threshold value which is higher than the first threshold value, then Figure 9As shown in FIG, the rotation is terminated when the second inertial mass 104 abuts against at least one of the first stop element 170, the second stop element 172, the third stop element 174, and the fourth stop element 176. Figure 9 In FIG. 1 , it is assumed that the dimensions of the MEMS accelerometer 100 are such that the vertical peripheral wall RA1 ″ abuts the second protruding area 170H. The first inertial mass 103 is in any case kept at a distance from the first and second outer main stop elements 162 , 164 .

[0104] As reference Figure 4 and Figure 5 As discussed, the above rotation causes the elastic potential energy stored in the first spring element 142 and the second spring element 144 to increase, thereby causing the elastic restoring force F m Increased, thereby reducing the possibility of static friction between the first inertial mass 103 and the first stopping element 170.

[0105] Similar considerations apply to the case (not shown) where the external acceleration a ext In addition to being parallel to axis X, its direction is the same as axis X. In this case, if the external acceleration a ext The modulus of the first inertial mass 103 and the second inertial mass 104 rotate in a fixed manner around the second inner main stop element 182. ext In the case where the modulus of exceeds the corresponding second threshold value, and assuming that a rotation occurs in the counterclockwise direction, for example, the first inertial mass 103 abuts against the second protruding area 176H.

[0106] On the contrary, when the external acceleration a ext Parallel to axis Y and in the same direction Figure 6 When the Y-axis shown is in the opposite direction, the following occurs.

[0107] The second inertial mass 104 remains stationary relative to the base because the first spring element 142 and the second spring element 144 are rigid in a direction parallel to the axis Y. In contrast, the first inertial mass 103 translates upward (at Figure 6 ), because the third spring element 152 and the fourth spring element 154 conform in a direction parallel to the axis Y. In particular, the translation of the first inertial mass 103 results in a deformation of the third spring element 152, which is extended, and a deformation of the fourth spring element 154, which is compressed.

[0108] At the external acceleration a extUnder the assumption that the modulus of is high enough (i.e. exceeds the corresponding first threshold), the translation continues until the first outer side wall P1 abuts against the protruding area 162V of the first outer main stop element 162, the protruding area 162V serving as the center of rotation of the first inertial mass 103, as shown Figure 10 As shown in . Regarding the direction of rotation, Figure 4 Related considerations apply. For example, in the following, it is assumed that the rotation occurs in the counterclockwise direction. In addition, if the external acceleration a ext If the modulus of exceeds the corresponding second threshold value (is higher than the corresponding first threshold value), the rotation is terminated when the first inertial mass 103 abuts against at least one of the first stop element 170, the second stop element 172, the third stop element 174, and the fourth stop element 176. Figure 11 In FIG. 1 , it is assumed that the size of the MEMS accelerometer 100 is such that the horizontal peripheral wall RA1 ′ abuts against the first protruding area 170V.

[0109] The above-mentioned rotation of only the first inertial mass 103 results in an increase in the elastic potential energy stored in the third spring element 152 and the fourth spring element 154, thereby resulting in an elastic restoring force F m Increased, thereby reducing the possibility of a stiction phenomenon occurring between the first inertial mass 103 and any one of the first, second, third, and fourth secondary stop elements 170 .

[0110] Similar considerations apply to the case (not shown) where the external acceleration a ext In addition to being parallel to axis Y, its direction is the same as axis Y. In this case, if the external acceleration a ext If the modulus of exceeds the corresponding first threshold, the first inertial mass 103 rotates around the protruding area 164V of the second outer main stop element 162. In addition, if the external acceleration a ext The modulus of exceeds the corresponding second threshold value, and assuming that the rotation occurs in the clockwise direction, for example, the rotation stops when the first inertial mass 103 abuts against the first protruding area 172V.

[0111] In practice, the first outer main stop element 162 and the second outer main stop element 164, as well as the first stop element 170, the second stop element 172, the third stop element 174, and the fourth stop element 176, form a first stop structure relative to axis Y. Similarly, the first inner main stop element 180 and the second inner main stop element 182, as well as the first stop element 170, the second stop element 172, the third stop element 174, and the fourth stop element 176, form a second stop structure relative to axis X. Furthermore, in this embodiment, the first stop structure and the second stop structure share the first stop element 170, the second stop element 172, the third stop element 174, and the fourth stop element 176. In this regard, embodiments in which the first inertial mass 103 is stopped against a second stop element different from that described are generally possible. In general, the secondary stop element with which the first inertial mass 103 effectively abuts depends not only on the direction of acceleration and the direction of subsequent rotation, but also on the shape and arrangement of the first stop element 170, the second stop element 172, the third stop element 174 and the fourth stop element 176, as well as the positioning of the rotation axis and the shape of the first inertial mass 103, which can be changed relative to what is described.

[0112] Ignoring the implementation details of stopping the rotation, the external acceleration a ext The measurement can be similar to the reference Figure 1A and 1B The described manner is thus based on the presence of a first variable capacitor C in the first additional opening 200. X and the second variable capacitor C X2 The value of its capacitance is along the external acceleration a ext and based on the first variable capacitor C present in the second additional opening 202. Y1 and the second variable capacitor C Y1 、C Y2 , its capacitance is along the external acceleration a ext The sensing axes of the MEMS accelerometer 100 are parallel to the X axis and the Y axis, respectively, and lie in the first symmetry plane SP1 and the second symmetry plane SP2, respectively.

[0113] Figure 12 An electronic device 340 including the MEMS accelerometer 100 is shown.

[0114] ASIC 343 may be provided in the same die as MEMS accelerometer 100. In a further embodiment (not shown), ASIC 343 is fabricated in a separate die and housed in the same package as MEMS accelerometer 100.

[0115] The electronic device 340 is, for example, a portable mobile communication device, such as a mobile phone, a PDA (personal digital assistant), a portable computer, a digital audio player with voice recording capability, a camera, or a controller for a video game; in detail, the electronic device 340 is generally capable of processing, storing and / or sending and receiving signals and information.

[0116] The electronic device 340 further comprises a microprocessor 344 that receives acceleration signals generated by the ASIC 343 based on detection by the MEMS accelerometer 100 and an input / output interface 345 equipped with a keyboard and a screen connected to the microprocessor 344. Furthermore, the electronic device 340 comprises a speaker 347 for generating sound on an audio output (not shown) and an internal memory 348 connected to the microprocessor 344.

[0117] The MEMS inertial sensor has various advantages. In particular, the MEMS inertial sensor disclosed herein can reduce the likelihood of stiction without increasing the overall size of the device or reducing the full range of the device.

[0118] Finally, it is obvious that modifications and variations may be made to the MEMS inertial sensor described and illustrated herein, without thereby departing from the scope of the present disclosure.

[0119] For example, the present MEMS inertial sensor may be used as a gyroscope, an inclinometer, or a vibrometer.

[0120] The shape of the protruding area defining the axis of rotation may vary from that described. More generally, as previously mentioned, the shape and arrangement of the outer and inner primary stop elements may vary from that described; similarly, the shape and arrangement of the secondary stop elements may vary from that described.

[0121] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above detailed description. Generally, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments and the full scope of equivalents to which such claims are entitled. Therefore, the claims are not limited by this disclosure.

Claims

1. A MEMS inertial sensor, comprising: Support structure; an inertial structure comprising at least one first inertial mass; a first elastic structure mechanically coupled to the first inertial mass and the support structure so that: when the support structure is subjected to a first acceleration parallel to a first direction, the first inertial mass can move relative to the support structure in a direction parallel to the first direction; as well as a first stop structure, fixed relative to the support structure and comprising at least a first main first-axis stop element and a second secondary first-axis stop element, wherein the first main first axis stop element is configured such that, if the first acceleration exceeds a first threshold value, the first inertial mass abuts against the first main first axis stop element and subsequently rotates about a first rotation axis defined by the first main first axis stop element, and The first first axis stop element is configured such that if the first acceleration exceeds a second threshold value higher than the first threshold value, the rotation of the first inertial mass is terminated when the first inertial mass abuts the first first axis stop element.

2. The MEMS inertial sensor according to claim 1, wherein the inertial structure further comprises a second inertial mass, the MEMS inertial sensor further comprising: a second elastic structure elastically coupled to the second inertial mass and the support structure and configured such that, when the support structure is subjected to a second acceleration parallel to a second direction, the second inertial mass can move relative to the support structure in a direction parallel to the second direction; wherein the first elastic structure is mechanically interposed between the first inertial mass and the second inertial mass and is configured such that: when the support structure is subjected to the second acceleration, the first inertial mass and the second inertial mass translate in a fixed manner in a direction parallel to the second direction, and The second elastic structure is configured such that: when the support structure is subjected to the first acceleration, the second inertial mass block remains substantially fixed relative to the support structure.

3. The MEMS inertial sensor of claim 2 , further comprising a second stopper structure fixed relative to the support structure and comprising at least a first primary second-axis stopper element and a second secondary second-axis stopper element, wherein the first main second-axis stop element is configured such that, if the second acceleration exceeds a third threshold value, the second inertial mass abuts against the first main second-axis stop element and subsequently rotates in a fixed manner relative to the first inertial mass about a second rotation axis defined by the first second-axis stop element, and The first second axis stop element is configured such that, if the second acceleration exceeds a fourth threshold value that is higher than the third threshold value, the rotation of the first inertial mass and the second inertial mass is terminated in a fixed manner when the second inertial mass abuts against the first second axis stop element.

4. The MEMS inertial sensor of claim 3 , wherein the first stopper structure further comprises a second primary first axis stop element and a second secondary second axis stop element, wherein the second main first axis stop element is configured such that, when the support structure is subjected to a third acceleration having a direction opposite to the first acceleration and being above a fifth threshold value, the first inertial mass abuts against the second main first axis stop element and subsequently rotates about a third rotation axis defined by the second main first axis stop element, and The second first-axis stopping element is configured such that, if the third acceleration exceeds a sixth threshold value that is higher than the fifth threshold value, the rotation of the first inertial mass around the third rotation axis is terminated when the first inertial mass abuts against the second first-axis stopping element.

5. The MEMS inertial sensor according to claim 4, wherein the second stopper structure further comprises a second primary second-axis stop element and a second secondary second-axis stop element, wherein the second main second-axis stop element is configured such that, when the support structure is subjected to a fourth acceleration having a direction opposite to the second acceleration and being above a seventh threshold value, the second inertial mass abuts against the second main second-axis stop element and subsequently rotates in a fixed manner relative to the first inertial mass about a fourth rotation axis defined by the second main second-axis stop element, and The second second-axis stopping element is configured such that, if the fourth acceleration exceeds an eighth threshold value that is higher than the seventh threshold value, the rotation of the first inertial mass and the second inertial mass is stopped in a fixed manner when the second inertial mass abuts against the second second-axis stopping element.

6. The MEMS inertial sensor according to claim 5, wherein the first inertial mass is penetrated by the main opening, wherein the second inertial mass and the first elastic structure extend within the main opening, and The first elastic structure includes a pair of elastic elements, which are symmetrical with respect to a first symmetry plane parallel to the second direction in a static state. Each elastic element in the pair of elastic elements is fixed to the first inertial mass block and the second inertial mass block, and the second inertial mass block is inserted between the elastic elements in the pair of elastic elements.

7. The MEMS inertial sensor according to claim 6, wherein the second inertial mass is penetrated by the first opening and the second opening, wherein the support structure comprises a first anchoring region and a second anchoring region, the first anchoring region and the second anchoring region being symmetrical with respect to a second symmetry plane parallel to the first direction and partially extending within the first opening and the second opening, respectively; and The second elastic structure includes a corresponding first elastic element and a corresponding second elastic element, wherein the corresponding first elastic element and the corresponding second elastic element are symmetrical with respect to the second symmetry plane in a static state and extend in the first opening and the second opening respectively, the first elastic element of the second elastic structure is fixed to the first anchoring area and the second inertial mass block, and the second elastic element of the second elastic structure is fixed to the second anchoring area and the second inertial mass block.

8. The MEMS inertial sensor of claim 7 , wherein the first main first-axis stop element and the second main first-axis stop element extend outside the first inertial mass, and each stop element includes a corresponding protruding area facing the first inertial mass, the protruding area of ​​the first main first-axis stop element defining the first rotational axis, and the protruding area of ​​the second main first-axis stop element defining the third rotational axis.

9. The MEMS inertial sensor according to claim 8, wherein the first main second-axis stopping element and the second main second-axis stopping element partially extend within the first and second secondary openings, respectively, and are symmetrically arranged with respect to a center portion of the second inertial mass in a stationary state, the first main second-axis stopping element and the second main second-axis stopping element respectively having a protruding shape and defining the second rotation axis and the fourth rotation axis. 10 . The MEMS inertial sensor of claim 9 , wherein the first and second primary second axis stop elements are fixed to the first and second anchor regions, respectively. 11 . The MEMS inertial sensor according to claim 9 , wherein the first and second first axis stopping elements, and the first and second second axis stopping elements are arranged outside the first inertial mass.

12. A MEMS inertial sensor, comprising: Support structure; An inertial structure comprising a first inertial mass block and a second inertial mass block; a first elastic structure mechanically coupled to the first inertial mass and the support structure so that: when the support structure is subjected to a first acceleration parallel to a first direction, the first inertial mass can move relative to the support structure in a direction parallel to the first direction; a second elastic structure elastically coupled to the second inertial mass and the support structure, and configured such that: when the support structure is subjected to a second acceleration parallel to a second direction, the second inertial mass can move relative to the support structure in a direction parallel to the second direction; a first stop structure fixed relative to the support structure and comprising at least a first primary first-axis stop element and a second secondary first-axis stop element; a spindle electrode fixed relative to the support structure and capacitively coupled to the first inertial mass to form a corresponding spindle capacitor, a capacitance of the spindle capacitor being indicative of the first acceleration; as well as A transverse-axis electrode is fixed relative to the support structure and capacitively coupled to the second inertial mass to form a corresponding transverse-axis capacitor, the capacitance of the transverse-axis capacitor being indicative of the second acceleration.

13. The MEMS inertial sensor according to claim 12, wherein: the first main first axis stop element being configured such that, if the first acceleration exceeds a first threshold value, the first inertial mass abuts against the first main first axis stop element and subsequently rotates about a first rotation axis defined by the first main first axis stop element, the first first axis stop element being configured such that, if the first acceleration exceeds a second threshold value that is higher than the first threshold value, a rotation of the first inertial mass is terminated when the first inertial mass abuts the first first axis stop element, The first elastic structure is mechanically interposed between the first inertial mass and the second inertial mass and is configured such that, when the support structure is subjected to the second acceleration, the first inertial mass and the second inertial mass translate in a fixed manner in a direction parallel to the second direction, and The second resilient structure is configured such that the second inertial mass remains substantially stationary relative to the support structure when the support structure is subjected to the first acceleration.

14. The MEMS inertial sensor of claim 13 , further comprising a second stopper structure fixed relative to the support structure and comprising at least a first primary second-axis stopper element and a second secondary second-axis stopper element, wherein the first main second-axis stop element is configured such that, if the second acceleration exceeds a third threshold value, the second inertial mass abuts against the first main second-axis stop element and subsequently rotates in a fixed manner relative to the first inertial mass about a second rotation axis defined by the first second-axis stop element, and The first second axis stop element is configured such that, if the second acceleration exceeds a fourth threshold value that is higher than the third threshold value, the rotation of the first inertial mass and the second inertial mass is terminated in a fixed manner when the second inertial mass abuts against the first second axis stop element.

15. The MEMS inertial sensor of claim 14, wherein the first stopper structure further comprises a second primary first axis stop element and a second secondary second axis stop element, wherein the second main first axis stop element is configured such that, when the support structure is subjected to a third acceleration having a direction opposite to the first acceleration and being above a fifth threshold value, the first inertial mass abuts against the second main first axis stop element and subsequently rotates about a third rotation axis defined by the second main first axis stop element, and The second first-axis stopping element is configured such that, if the third acceleration exceeds a sixth threshold value that is higher than the fifth threshold value, the rotation of the first inertial mass around the third rotation axis is terminated when the first inertial mass abuts against the second first-axis stopping element.

16. An electronic device comprising: MEMS inertial sensors, including: Support structure; an inertial structure comprising at least one first inertial mass; a first elastic structure mechanically coupled to the first inertial mass and the support structure so that the first inertial mass can move relative to the support structure in a direction parallel to the first direction when the support structure is subjected to a first acceleration parallel to the first direction; and a first stop structure, fixed relative to the support structure and comprising at least a first main first-axis stop element and a second secondary first-axis stop element, wherein the first main first axis stop element is configured such that, if the first acceleration exceeds a first threshold value, the first inertial mass abuts against the first main first axis stop element and subsequently rotates about a first rotation axis defined by the first main first axis stop element, and wherein the first first axis stop element is configured such that: if the first acceleration exceeds a second threshold value that is higher than the first threshold value, a rotation of the first inertial mass is terminated when the first inertial mass abuts the first first axis stop element; an ASIC coupled to the MEMS inertial sensor; and A processing unit is coupled to the ASIC.

17. The electronic device according to claim 16, wherein the inertial structure further comprises a second inertial mass, and the MEMS inertial sensor further comprises: a second elastic structure elastically coupled to the second inertial mass and the support structure and configured such that, when the support structure is subjected to a second acceleration parallel to a second direction, the second inertial mass can move relative to the support structure in a direction parallel to the second direction; wherein the first elastic structure is mechanically interposed between the first inertial mass and the second inertial mass and is configured such that: when the support structure is subjected to the second acceleration, the first inertial mass and the second inertial mass translate in a fixed manner in a direction parallel to the second direction, and The second elastic structure is configured such that: when the support structure is subjected to the first acceleration, the second inertial mass block remains substantially fixed relative to the support structure.

18. The electronic device of claim 17 , wherein the MEMS inertial sensor further comprises a second stop structure fixed relative to the support structure and comprising at least a first primary second-axis stop element and a second secondary second-axis stop element, wherein the first main second-axis stop element is configured such that, if the second acceleration exceeds a third threshold value, the second inertial mass abuts against the first main second-axis stop element and subsequently rotates in a fixed manner relative to the first inertial mass about a second rotation axis defined by the first second-axis stop element, and The first second axis stop element is configured such that, if the second acceleration exceeds a fourth threshold value that is higher than the third threshold value, the rotation of the first inertial mass and the second inertial mass is terminated in a fixed manner when the second inertial mass abuts against the first second axis stop element.

19. The electronic device of claim 18, wherein the first stopper structure further comprises a second primary first axis stop element and a second secondary second axis stop element, wherein the second main first axis stop element is configured such that, when the support structure is subjected to a third acceleration having a direction opposite to the first acceleration and being above a fifth threshold value, the first inertial mass abuts against the second main first axis stop element and subsequently rotates about a third rotation axis defined by the second main first axis stop element, and The second first-axis stopping element is configured such that, if the third acceleration exceeds a sixth threshold value that is higher than the fifth threshold value, the rotation of the first inertial mass around the third rotation axis is terminated when the first inertial mass abuts against the second first-axis stopping element.

20. The electronic device of claim 19, wherein the second stopper structure further comprises a second primary second axis stop element and a second secondary second axis stop element, wherein the second main second-axis stop element is configured such that, when the support structure is subjected to a fourth acceleration having a direction opposite to the second acceleration and being above a seventh threshold value, the second inertial mass abuts against the second main second-axis stop element and subsequently rotates in a fixed manner relative to the first inertial mass about a fourth rotation axis defined by the second main second-axis stop element, and The second second-axis stopping element is configured such that, if the fourth acceleration exceeds an eighth threshold value that is higher than the seventh threshold value, the rotation of the first inertial mass and the second inertial mass is stopped in a fixed manner when the second inertial mass abuts against the second second-axis stopping element.

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