CN219869736U

CN219869736U - Microelectromechanical gyroscope and microelectromechanical device

Info

Publication number: CN219869736U
Application number: CN202320081825.5U
Authority: CN
Inventors: P·费德利; L·奎利诺尼; P·卡鲁里; L·G·法罗尼
Original assignee: STMicroelectronics SRL
Current assignee: STMicroelectronics SRL
Priority date: 2022-01-14
Filing date: 2023-01-11
Publication date: 2023-10-20
Anticipated expiration: 2033-01-11
Also published as: CN116448087A

Abstract

Embodiments of the present disclosure relate to microelectromechanical gyroscopes and microelectromechanical devices. A microelectromechanical gyroscope, comprising: a substrate having a top surface; a movable mass suspended above the substrate; a first stator element and a second stator element suspended between the movable mass and a top surface of the substrate; a central mechanical anchor structure coupled to the substrate, the central anchor structure including a first portion coupled to the substrate, the first portion being positioned between the first stator element and the second stator element in a first direction, the central anchor structure including a second portion coupled to the first stator element and the second stator element, the first portion being positioned between the second portion and the substrate in a second direction, the second direction being transverse to the first direction; and an elastic element coupling the movable mass to the central mechanical anchoring structure. Utilizing embodiments of the present disclosure advantageously allows for eliminating drift in the electrical properties of the detection structure caused by deformation of the substrate.

Description

Microelectromechanical gyroscope and microelectromechanical device

Technical Field

The present disclosure relates to a microelectromechanical (MEMS, microelectromechanical sensor) gyroscope having an out-of-plane detection motion with improved electrical characteristics, in particular improved stability with respect to stresses or external stimuli acting as a disturbance with respect to the quantity to be detected (angular velocity).

Background

MEMS gyroscopes are known whose detection structure comprises at least one movable mass, the so-called "rotor mass", suspended above a substrate and having a main extension plane parallel to the horizontal plane and to the top surface of the same substrate in a rest state.

When rotation at a certain angular velocity (the value of which is to be detected) is applied to a moving mass of a MEMS gyroscope driven at a linear velocity, the moving mass senses a fictive force called coriolis force, which determines its displacement in a direction perpendicular to the linear driving velocity and in a direction of an axis of rotation. The movable mass is supported by a resilient element which allows the movable mass to move in the direction of the imaginary force. According to hooke's law, displacement is proportional to this fictive force, thus representing coriolis force and angular velocity values.

In particular, in the present case, for gyroscopes with out-of-plane motion, a linear drive is carried out along a first axis of the horizontal plane, and the angular velocity is detected around a second axis of the horizontal plane orthogonal to the above-mentioned first axis, so that the displacement of the moving mass due to the coriolis effect occurs along a vertical axis z in a direction orthogonal to the same horizontal plane.

For example, the displacement of the moving mass can be detected capacitively, and the change in capacitance caused by the movement of the moving mass relative to a fixed detection electrode (so-called "stator element") forming at least one detection capacitor with the same moving mass is determined under resonance conditions.

The movable masses are coupled to the respective rotor anchors (integrated with the substrate) by elastic elements that allow their driving movement and their movement for angular velocity detection.

The stator elements are integrally coupled to the substrate by respective stator anchors so as to be capacitively coupled to the rotor and form a detection capacitor, the capacitive changes of which are indicative of the detected angular velocity.

In particular, in the detection structure, the rotor and stator anchors have the dual function of a mechanical anchoring towards the substrate and an electrical coupling for biasing the respective stator element and movable mass and for detecting the capacitive change signal.

In a known manner, the detection structure of the MEMS gyroscope is housed in a package, typically together with a corresponding ASIC (application specific integrated circuit) electronic circuit; packaging is the mechanical and electrical interface of the MEMS gyroscope towards the outside, for example towards the electronics in which the same MEMS gyroscope is used.

A problem affecting MEMS gyroscopes (and MEMS sensors typically having capacitive sensing structures) is due to measurement errors that may occur in the event of stress and deformation, in particular due to interactions with the package, such as stresses and deformations induced in the respective sensing structure when temperature and/or environmental conditions change or due to mechanical stresses.

For example, due to the different coefficients of thermal expansion and different young's modulus values of the different materials from which the MEMS sensor is fabricated, the packaging of the MEMS sensor is subject to deformation with temperature changes, which may result in a corresponding deformation of the substrate of the detection structure contained in the same packaging; similar deformations may occur due to aging of the material, or due to specific externally induced stresses, for example when the package is soldered on a printed circuit board, or due to moisture absorption of the material constituting the same package.

As schematically shown in fig. 1, in the presence of deformations of the substrate 2, for example due to thermal stresses associated with temperature gradients, a deformation (or curvature) of the top surface 2a of the same substrate 2 (which is shown in an emphasized manner in fig. 1 for the sake of clarity) may occur, for example, with respect to a stationary initial condition, i.e. without the angular velocity to be detected, a variation of the mutual distance of the stator anchors 3a,3b (with the stator elements integrally coupled thereto) and the rotor anchors 4 (with the moving mass of the detection structure elastically coupled thereto).

Thus, in a stationary state, an undesired change in the capacitance of the detection capacitor formed between the same moving mass and the stator electrode occurs, resulting in a change in the so-called Zero Rate Level (ZRL) of the MEMS gyroscope. The variation may also vary as a function of temperature or, in general, as a function of all external effects that can cause deformations of the same substrate 2.

In essence, the variation of the output signal at rest (the so-called "drift") provided by the MEMS gyroscope, the ZRL level described above, and the errors that occur in the angular velocity detection. In general, the described phenomenon determines the instability of the detection output provided by a MEMS gyroscope during the lifetime of the same MEMS gyroscope.

To overcome this drawback, various solutions have been proposed, some providing mechanical optimization of the detection structure, others providing electronic compensation; however, the known solutions are not entirely satisfactory, as they generally have a complex structure and/or require high energy consumption.

Disclosure of Invention

It is an object of the present disclosure to provide a microelectromechanical gyroscope and a microelectromechanical device to at least partially solve the above-mentioned problems of the prior art.

An aspect of the present disclosure provides a microelectromechanical gyroscope, comprising: a substrate having a top surface; a movable mass suspended above the substrate; a first stator element and a second stator element suspended between the movable mass and the top surface of the substrate; a central mechanical anchor structure coupled to the substrate, the central anchor structure comprising a first portion coupled to the substrate, the first portion being located between the first stator element and the second stator element in a first direction, the central anchor structure comprising a second portion coupled to the first stator element and the second stator element, the first portion being located between the second portion and the substrate in a second direction, the second direction being transverse to the first direction; and an elastic element coupling the movable mass to the central mechanical anchoring structure.

According to one or more embodiments, wherein the movable mass comprises: a frame having a window; and first and second detection portions extending from the frame to the window, the first and second stator elements having respective detection portions facing the first and second detection portions of the movable mass, respectively.

According to one or more embodiments, comprising a first structural layer and a second structural layer on top of each other, the first structural layer being at a smaller distance from the top surface of the substrate in the second direction than the second structural layer, the first and second detection portions of the movable mass being in the second structural layer, and the first and second stator elements being in the first structural layer.

According to one or more embodiments, wherein the first stator element and the second stator element comprise respective connection portions between the respective detection portions of the first stator element and the second stator element and the central mechanical anchoring structure, the connection portions being coupled to the second portion of the central mechanical anchoring structure in the second structural layer by respective dielectric regions.

In accordance with one or more embodiments, wherein the first portion is in the first structural layer, the first portion is coupled to the second portion and mechanically and electrically coupled to a rotor connection conductive element on the top surface of the substrate, the connection portions of the first stator element and the second stator element are separated from the first portion by a groove.

According to one or more embodiments, wherein the detection portions of the first stator element and the second stator element extend towards a wall of the frame of the movable mass, the wall having a circular arc shape.

According to one or more embodiments, an electrical connection element is included in the second structural layer, the electrical connection element having a first end mechanically and electrically coupled to the connection portions of the first and second stator elements, and a second end connected to a respective electrical anchor, the electrical anchor being mechanically and electrically coupled to a respective stator connection conductive element on the top surface of the substrate.

According to one or more embodiments, a first and a second conductive path are included for electrical connection of the first and the second stator element, the respective electric anchors, the respective stator connection conductive elements, the respective electrical connection elements and the respective connection portions; and a third conductive path for electrical connection of the movable mass, the mechanical anchoring structure, the rotor connecting conductive element and the elastic element.

Another aspect of the present disclosure provides a device comprising: a substrate; a central anchor, a first portion of the central anchor coupled to the substrate in a central region of the substrate, the central anchor having a second portion opposite the first portion; a movable mass, comprising: a first outer edge opposite the second outer edge; a central opening between the first outer edge and the second outer edge, the central anchor in the central opening, the movable mass coupled with the second portion of the central anchor; a protrusion extending from the first edge into the central opening toward the central anchor, the protrusion having a first end spaced apart from and adjacent the central anchor; a stator element suspended between the protrusion and the substrate, the stator element coupled to the central anchor by a dielectric region on a first surface of the central anchor facing the substrate; an electric anchor on the substrate and in the central opening of the movable mass, the electric anchor being coupled to the stator element; a first resilient element coupling the movable mass to the central anchor in the central opening, the first resilient element extending from the second portion of the central anchor to the movable mass; a drive mass coupled to the substrate; and a second elastic element coupling the driving mass to the movable mass.

According to one or more embodiments, wherein the movable mass has a first surface facing the substrate, the first surface having a wall facing the central opening, the wall having a concave curvature, the protrusion extending from the wall.

According to one or more embodiments, wherein the first side of the stator element extends towards the wall in the first surface of the movable mass and has substantially the same shape as the wall.

According to one or more embodiments, wherein the first and second elastic elements are separated from each other by the movable mass.

The second portion of the central anchor includes a first side coupled with the movable mass, the first side being transverse to a second side of the central anchor, the second side facing the protrusion of the movable mass.

According to one or more embodiments, wherein a portion of the stator element is located in the central opening of the movable mass.

Yet another aspect of the present disclosure provides a microelectromechanical device, comprising: a substrate; fixing the mechanical structure; a moving mass, comprising: an opening comprising a body aligned with the fixed mechanical structure and a plurality of extensions away from the body; a first surface opposite a second surface, the first surface of the movable mass facing the substrate, a first side of the movable mass between a first and a second one of the plurality of extensions of the opening, and a second side of the movable mass between a third and a fourth one of the plurality of extensions of the opening; and a first stator element and a second stator element coupled to the fixed mechanical structure, the first stator element being located between the first side of the movable mass and the substrate, and the second stator element being located between the second side of the movable mass and the substrate.

According to one or more embodiments, a connection element is included that is coupled between the stator element and an electrical anchor on the substrate, and the connection element is located in the opening of the movable mass.

According to one or more embodiments, a spring assembly is included, a first of the spring assemblies coupling the movable mass to the fixed mechanical structure.

According to one or more embodiments, a driving mass coupled to the movable mass via a second one of the elastic assemblies is included, the driving mass being located at an opposite end of the movable mass.

According to one or more embodiments, wherein the driving mass comprises a first driving electrode and a second driving electrode fixed to the substrate, the first driving electrode and the second driving electrode being adjacent to each other in a pattern.

According to one or more embodiments, wherein the driving mass is elastically coupled to the substrate via a folded elastic element.

Utilizing embodiments of the present disclosure advantageously allows for eliminating drift in the electrical properties of the detection structure caused by deformation of the substrate.

Drawings

For a better understanding of the present disclosure, preferred embodiments thereof will now be described, by way of non-limiting example only, wherein:

FIG. 1 is a schematic diagram associated with a portion of a detection structure of a MEMS gyroscope in which there is deformation of a corresponding substrate;

FIG. 2A is a schematic plan view of a detection structure of a MEMS gyroscope according to a first embodiment of the present solution;

FIG. 2B is a top perspective view of the detection structure of FIG. 2A;

FIG. 3 is a schematic cross-sectional view of an anchoring structure of the MEMS gyroscope of FIGS. 2A and 2B;

FIG. 4 is a schematic cross-sectional view of the anchor structure of FIG. 3 with a corresponding substrate deformed;

FIG. 5 is a schematic plan view of a detection structure of a MEMS gyroscope according to a second embodiment of the present solution;

FIG. 6 is a schematic plan view of a portion of a detection structure of a MEMS gyroscope according to another embodiment of the present solution; and

fig. 7 is a schematic block diagram of an electronic device incorporating a MEMS sensor device according to another aspect of the present solution.

Detailed Description

As will be described in detail below, one aspect of the present solution envisages manufacturing the detection structure of the MEMS gyroscope in such a way that the movable mass (rotor) and the fixed electrode (stator element) are mechanically coupled to the substrate by means of a single and unique (or monolithic) mechanical anchoring structure, said fixed electrode being capacitively coupled to the movable mass to define at least one detection capacitor (integrally coupled to the same substrate); in this way, the possible deformations caused by the encapsulation in the substrate are reflected in an equivalent way on the moving mass and the stator element, so that the detection is effectively insensitive to deformations, avoiding possible modifications (so-called drift of the ZRL level) in the output signal provided by the same MEMS gyroscope at rest.

Thus, by introducing a dedicated electrical anchor different from the mechanical anchor, a distinction is made between mechanical anchors and electrical anchors defining at least some structural elements of the detection structure, in particular the stator elements, for biasing the same stator elements and for detecting the capacitance change signal; as described below, these electrical anchors are electrically coupled to a single mechanical anchor structure so as to define an electrical path for biasing and for detecting a capacitance change signal, while representing a completely negligible mechanical coupling.

According to one aspect of the present solution, the detection structure comprises two overlying structural layers of semiconductor material (in particular epitaxial silicon) that are independent of each other and are suitably processed (in particular by trench etching and removal of the sacrificial layer) to define at least partially overlying structural elements of the detection structure.

As will be described in detail below, at least a part of the moving mass of the detection structure is defined in the top structural layer, and the connection of the stator element and the same stator element towards a single anchoring structure, in particular for the integral mechanical coupling of the stator element to the same single anchoring structure, is defined in the bottom structural layer, which is arranged below the top structural layer (or interposed between the substrate and the same top structural layer).

The manufacturing of the detection structure by the aforementioned overlapping structure layers may be performed, for example, by a manufacturing process described in detail in US2021/0363000 A1.

Briefly, the process provides for growing a first epitaxial layer on a substrate, such as monocrystalline silicon, which is thick, overlying a first sacrificial layer of dielectric material, and then partially removed by etching (e.g., by hydrofluoric acid vapor). The first sacrificial layer has an opening therein defining an anchor region for the first epitaxial layer to the substrate.

The first epitaxial layer is a first structural layer in which a first trench (which is empty, or subsequently filled with a dielectric material) is formed, for example by dry etching of silicon, the first trench defining a structural element of the detection structure or a bottom portion of the same structural element (i.e. closer to the substrate); under the first sacrificial layer, conductive regions (defining pads and electrical interconnections) are formed at the anchor regions to the substrate of the first epitaxial layer so as to allow electrical biasing of the structural elements.

Subsequently, a fabrication process provides for forming a second sacrificial layer of dielectric material over the first epitaxial layer and defining the same second sacrificial layer to form sacrificial regions separated from each other by openings.

Then forming a second epitaxial layer having, for example, a smaller thickness than the first epitaxial layer on the same first epitaxial layer and on the sacrificial region; the second epitaxial layer is in direct contact with the first epitaxial layer at the aforementioned opening and is a second structural layer, wherein the structural elements of the detection structure or a top portion of the same structural elements (i.e. away from the substrate) are defined by forming a second trench.

The process then provides for partial or complete removal of the sacrificial region again by etching (e.g., by hydrofluoric acid vapor) to at least partially release the structural elements of the detection structure.

After this etching, regions of the second epitaxial layer may optionally: in direct contact (mechanically and electrically) with the underlying region of the first epitaxial layer and possibly with the underlying substrate; a void (space) spaced from the underlying first epitaxial layer and suspended above the same first epitaxial layer; or the dielectric region left by etching the second sacrificial layer is coupled to (and electrically isolated from) the same first epitaxial layer.

Referring to the plan view of fig. 2A, the perspective view of fig. 2B and the detailed cross-sectional view of fig. 3, a first embodiment of the present solution will now be described, which relates to a microelectromechanical (MEMS) gyroscope 10 of the single-axis type for detecting an angular velocity Ω about a first axis x of a horizontal plane xy _x 。

The detection structure 11 of the MEMS gyroscope 10 has a centre O and a symmetrical arrangement in a horizontal plane xy with respect to a first axis x and a second horizontal axis y.

The detection structure 11 comprises a movable (or rotor) mass 12 arranged to be suspended above a substrate 14 of semiconductor material (in particular silicon) having a top surface 14 a; at rest, movable mass 12 has a main extension in horizontal plane xy and is arranged parallel to top surface 14a of substrate 14.

The movable mass 12 has a frame 15, which in this example is substantially rectangular in a horizontal plane xy, which frame defines a window or opening 16 internally; the same moving mass 12 also comprises first and second detection portions 12a,12b extending from the frame 15 within the window 16, suspended in cantilever fashion with respect to the substrate 14, in the example having a substantially trapezoidal shape, with inclined sides extending radially towards the centre O.

Movable mass 12 is elastically coupled to a single anchoring structure 20 (described in greater detail below) by an anchoring elastic element 18, which anchoring structure 20 is arranged centrally of window 16 and is integral with substrate 14, and which anchoring elastic element 18 has a linear extension along a second horizontal axis y and is curved in a horizontal plane xy and twisted about the same second horizontal axis y.

The frame 15 of the moving block 12 is provided by stacking the above-described first and second structural layers, denoted by L1 and L2 in fig. 3, while the first and second detecting portions 12a,12b are provided only in the second structural layer L2 (arranged at a greater distance with respect to the top surface 14a of the substrate 14).

In particular, the frame 15 has, at the coupling with the first detection portion 12a and the second detection portion 12b, below the same detection portion a substantially vertical wall 17 with an extension perpendicular to the horizontal plane xy (along the vertical axis z); the wall 17 has a circular arc-shaped cross section in the horizontal plane xy (as indicated by a broken line in fig. 2A).

The detection structure 11 further comprises a first and a second driving electrode 22a,22b arranged on opposite sides of the frame 15 of the movable mass 12 with respect to the first horizontal axis x, externally with respect to the same frame 15.

These drive masses 22a,22b define internally a frame to which the first drive electrode 23 is coupled in an interdigitated arrangement with the second drive electrode 24, the frame being fixed and integrated with the substrate. The above-mentioned driving masses 22a,22b are elastically coupled to anchors 25 integrated with the substrate 14 by folded elastic elements 26, which folded elastic elements 26 allow their driving movements to translate linearly in opposite directions along the first horizontal axis x, in this example, due to the bias of the above-mentioned first and second driving electrodes 23, 24.

The same driving mass 22a,22b is coupled to the frame 15 of the movable mass 12 on opposite sides with respect to the first horizontal axis x by coupling elastic elements 27a,27b, which in this example have a linear extension along the second horizontal axis y and yield to bending in the horizontal plane xy and torsion about the second horizontal axis y.

Detection structure 11 further comprises first and second stator elements 28a,28b, arranged within window 16, on opposite sides with respect to second horizontal axis y, arranged to be suspended above substrate 14 and below movable mass 12, formed in first structural layer L1.

In particular, each stator element 28a,28b comprises a respective detection portion 29a,29b arranged to be suspended above the top surface 14a of the substrate 14, facing under the respective detection portion 12a,12b of the moving mass 12, to form a respective detection capacitor, having a flat and parallel face.

Each detection portion 29a,29b has a shape substantially corresponding to the overlapped respective detection portion 12a,12b of the movable mass 12, in this example substantially trapezoidal, with the main base having the shape of an arc in the horizontal plane xy so as to correspond to the facing wall 17 (at the level of the first structural layer L1) of the frame 15 of the movable mass 12.

Each stator element 28a,28b further comprises a respective connecting portion 30a,30b interposed in the horizontal plane xy between the respective detecting portion 29a,29b and the single anchoring structure 20 and integrally coupled to the same single anchoring structure 20. In particular, these connecting portions 30a,30b are separated from the single anchoring structure 20 in the horizontal plane xy by separation grooves 31.

In more detail, in the embodiment shown, also as shown in fig. 3, the above-mentioned respective connection portions 30a,30b are coupled to the overlying top 20a of the single anchoring structure 20 (provided in the second structural layer L2) by respective dielectric regions 32, in particular silicon oxide, the dielectric regions 32 defining, in addition to the mechanical connection, an electrical insulation between the stator elements 28a,28b and the movable mass 12 (rotor). Thus, this dielectric region 32 is interposed in contact between the above-mentioned connection portions 30a,30b of the stator elements 28a,28b and the opposite surfaces of the overlying top 20a of the single anchoring structure 20.

The single anchor structure 20 further comprises a bottom 20b provided in the first structural layer L1, which bottom 20b is integrally coupled to the top 20a and is also mechanically and electrically coupled to conductive pads or tracks R for rotor connection arranged on the top surface 14a of the substrate 14.

As schematically shown in the same fig. 3, each connection portion 30a,30b is also coupled to a respective electrical anchor 34 by a respective electrical connection element (or "wire") 35, which electrical anchor 34 is distinct and separate with respect to the single anchoring structure 20.

In detail (see for example fig. 2A), these electrical connection elements 35 are made of thin and long portions which are serpentine folded in the example provided in the second structural layer L2, configured in such a way that they represent a completely negligible mechanical coupling between the respective connection portions 30a,30b and the electrical anchors 34.

In the embodiment shown, these electrical connection elements 35 have a first end mechanically and electrically connected integrally with the underlying connection portions 30a,30b and a second end connected with the respective electrical anchors 34. Furthermore, for each connection portion 30a,30b, there are two electrical anchors 34 (and corresponding electrical connection elements 35) arranged on opposite sides with respect to the first horizontal axis x, close to the single anchoring structure 20.

In particular, in this case, the electrical anchor 34 perpendicularly crosses the connection portion 30a,30b of the respective stator element 28a,28b, the electrical anchor 34 being separated from the connection portion 30a,30b by a separation groove 37.

The electrical anchors 34 are portions of the first structural layer L1 (in this example, portions of the second structural layer L2) that are directly connected (by epitaxial silicon connection portions) to respective underlying conductive pads or traces (represented by S1, S2 in fig. 3) for stator connection disposed on the top surface 14a of the substrate 14.

Essentially, separate and distinct conductive paths are thus defined in the detection structure 11 for detection of the electrical bias and capacitance change signals, in particular: first and second electrically conductive paths for electrical connection of the first and second stator elements 28a,28b, including the aforementioned electrical anchors 34 and corresponding stator connection pads S1, S2, the corresponding electrical connection elements 35 and connection portions 30a,30b of the stator elements 28a,28 b; and a third conductive path for the electrical connection of movable mass 12, comprising a single anchoring structure 20 and a corresponding rotor connection pad R and anchoring elastic element 18.

During operation, driving movement of driving structures 22a,22b along first horizontal axis x (in opposite directions) causes rotation of movable mass 12 about vertical axis z (and center O); in particular, these driving movements are allowed by the deformation (bending) of the coupling elastic elements 27a,27b and the anchoring elastic element 18 in the horizontal plane xy.

In the presence of angular velocity Ω about a first horizontal axis x _x Due to the coriolis effect, moving mass 12 also undergoes a rotation about second horizontal axis y, resulting in its displacement from horizontal xy and a differential capacitance change of the detection capacitor formed between the same moving mass 12 and stator elements 28a,28 b; in particular, this detection movement is allowed by the deformation (torsion) of the anchoring elastic element 18.

Advantageously, the presence of a single anchoring structure 20 allows to substantially eliminate the relative displacement between the rotor and the stator due to stresses or external stimuli.

In particular, as schematically shown in fig. 4, even in the presence of deformations of the substrate 14, for example due to thermal stresses associated with positive temperature gradients, and of the resulting deformations of the top surface 14a of the same substrate 14, in the rest state, in the absence of external angular velocities (in other words, in the absence of variations in the facing distance at rest), substantially no corresponding movements occur between the movable mass 12 and the stator elements 28a,28 b. The stator elements 28a,28b and movable mass 12 described above are in fact forced to move together in an integral manner by means of integral coupling with a single anchoring structure 20. As a result, it is advantageous that no undesired modification of the output signal at rest provided by the microelectromechanical gyroscope 10 occurs, as substantially no change in the "zero g level" occurs.

It is also emphasized that possible deformations of the substrate 14 at the electrical anchors 34 (with respect to the position of the aforementioned single anchor structure 20) are elastically absorbed by the electrical connection element 35 in a complete manner, and therefore do not affect the same single anchor structure 20 and do not cause undesired variations of the detection signal provided at the output by the MEMS gyroscope 10.

With reference to the plan view of fig. 5, a second embodiment of the present solution will now be described, which relates to a MEMS gyroscope 10 of the biaxial type for detecting the angular velocity Ω of a first horizontal axis x about a horizontal plane xy _x And another angular velocity Ω about a second horizontal axis y of the same horizontal plane xy _y 。

As is apparent from the examination of fig. 5 described above, the arrangement of the detection structures 11 is substantially identical to the arrangement of the first single-axis embodiment described above.

In this case, the moving block 12 further comprises third and fourth detection portions 12c,12d extending from the frame 15 within the window 16, suspended in a cantilever manner with respect to the substrate 14, in this case having substantially an arc shape in the horizontal plane xy (the first and second detection portions 12a,12b also have the same arc shape here).

In this case, the movable mass 12 is elastically coupled to the single anchoring structure 20 by a further anchoring elastic element 18, which anchoring elastic element 18 has a linear extension along a first horizontal axis x of the horizontal plane xy and yields to bending in the horizontal plane xy and torsion about the same first horizontal axis x. It should be noted that in this embodiment, the anchoring elastic members 18 extend from the respective detection portions 12a-12d towards the single anchoring structure 20.

The detection structure 11 further comprises third and fourth stator elements 28c,28d arranged within the window 16, on opposite sides with respect to the first horizontal axis x, arranged to be suspended above the substrate 14 and below the inertial mass 12, again formed in the first structural layer L1.

In particular, each stator element 28c,28d comprises a respective detection portion 29c,29d arranged to be suspended above the top surface 14a of the substrate 14, facing underneath the respective detection portion 12c,12d of the moving mass 12, to form a respective detection capacitor having flat and parallel faces.

In this case, each further stator element 28c,28d further comprises a respective connecting portion 30c,30d, said connecting portion 30c,30d being interposed in the horizontal plane xy between the respective detecting portion 29c,29d and the single anchoring structure 20 and being integrally coupled to the same single anchoring structure 20.

Similar to what has been previously discussed, each connection portion 30c,30d is coupled to the overlying top portion 20a of a single anchor structure 20 (disposed in the second structural layer L2) by a dielectric region 32, in particular silicon oxide.

As previously mentioned, each connection portion 30c,30d is also coupled to a respective electrical anchor 34 by a respective electrical connection element 35, the electrical anchors 34 being distinct and separate with respect to the individual anchoring structures 20. Likewise, these electrical connection elements 35 have a first end mechanically and electrically connected integrally with the underlying connection portions 30c,30d and a second end connected with a corresponding electrical anchor 34 provided in the second structural layer L2.

It should be noted that in this embodiment the connecting portions 30a-30d of the respective stator elements 28a-28d are traversed in the horizontal plane xy by the anchoring elastic elements 18.

In particular, in this embodiment, there are four dielectric regions 32 (in this case having a substantially square cross section in the horizontal plane xy) arranged at the vertices of a single anchoring structure 20, each dielectric region 32 integrally coupling two connecting portions 30a-30d of adjacent stator elements 28a-28d to the top 20a of a single anchoring structure 20.

Furthermore, in this second embodiment, the coupling elastic elements 27a,27b that elastically couple the driving masses 22a,22b to the moving mass 12 have a folded shape to allow the moving mass 12 to rotate not only about the second horizontal axis y but also about the first horizontal axis x of the horizontal plane xy.

The operation of the detecting structure 11 is substantially unchanged with respect to what has been described previously, except in the presence of an angular velocity Ω about the second horizontal axis y _y Due to the coriolis effect, moving mass 12 also undergoes rotation about first horizontal axis x, resulting in a change in the differential capacitance of the detection capacitor formed between the same moving mass 12 and the further stator elements 28c,28d Performing chemical treatment; in particular, this detection movement is allowed by the torsional deformation of the further anchoring elastic element 18.

Advantageously, due to the angular velocity Ω about the first horizontal axis x _x And an angular velocity Ω about a second horizontal axis y _y The resulting detection movement of the movable mass is substantially decoupled.

Another variant embodiment schematically shown in fig. 6 provides, in a horizontal plane xy, different shapes of the facing surfaces of the frame 15 of the mobile mass 12 and of the stator elements 28a,28b (the description applies similarly to the stator elements 28c,28 d), in particular to the corresponding detection portions 29a,29 b.

In this embodiment, these facing surfaces have the shape of a regular polygon in the horizontal plane xy, instead of the arc of a circle.

In the example shown in fig. 6 above, the stator elements 28a,28b together define a regular hexagon in the horizontal plane xy. Accordingly, the frame 15 also has internally a surface facing the aforementioned stator elements 28a,28b, said stator elements 28a,28b having a generally hexagonal shape in the horizontal plane xy.

In this embodiment, the operating principle of the detection structure 11 is unchanged from that discussed above. However, proper sizing may be required to avoid possible impact between the aforementioned facing surfaces during the driving motion of the moving mass 12.

For example, in the case of the aforementioned hexagons, the following relationship is respectively satisfied between the aforementioned frame 15 of the mobile mass 12 and the facing sides LR and LS of the aforementioned stator elements 28a,28 b:

the driving rotation angle of the movable mass 12 about the vertical axis z will be less than or equal to 30 ° in order to avoid the aforementioned impact between the opposite surfaces.

In any case, therefore, the circular shape of the facing surfaces in the horizontal plane xy is preferred and advantageous, as it ensures that in all conditions there is no impact between the same facing surfaces during the driving of the moving mass 12.

The circular shape also avoids the presence of a possible electrical common mode due to variations in the opposing surfaces, which may relatively occur in the case of polygonal embodiments (in the case of non-perfect symmetry of the detection structure 11).

Referring to fig. 7, an electronic device 40 is now described in which the microelectromechanical gyroscope 10 may be used.

In addition to the above-described detection structure 11, the microelectromechanical gyroscope 10 also comprises an ASIC circuit 43, which ASIC circuit 43 provides a corresponding read interface (and which ASIC circuit 43 may be made in the same die on which the detection structure 11 is provided, or in a different die, which die may in any case be housed in the same package).

The electronic device 40 is for example a portable mobile communication device, such as a mobile phone, a PDA (personal digital assistant), a portable computer, but may also be a digital audio player with voice recording capabilities, a photo or video camera, a video game controller or the like; electronics 40 are generally capable of processing, storing and/or transmitting and receiving signals and information.

The electronic device 40 includes: a microprocessor (CPU) 44 that receives signals detected by the microelectromechanical gyroscope 10; and an input/output interface 45, for example provided with a keyboard and a display, coupled to the microprocessor 44. In addition, the electronic device 40 may include an internal memory 48 operatively coupled to the microprocessor 44.

The advantages of the microelectromechanical gyroscope according to the solution are apparent from the foregoing description.

In any case, it is emphasized again that the present solution allows to substantially eliminate the drift of the electrical properties of the detection structure 11 caused by the deformation of the substrate 14 due to external stresses and excitations, for example due to temperature variations or mechanical stresses, for example by soldering to a printed circuit board or other reasons (for example ageing or moisture absorption).

The detection structure 11 is therefore extremely stable, irrespective of the operating conditions and the assembly in the respective package.

Furthermore, for example, in terms of sensitivity, the detection performance is generally unchanged from conventional solutions, since the detection principle is not modified, just as the shape and arrangement of the detection electrodes with respect to the inertial mass is not substantially modified.

Finally, it is clear that modifications and variations may be made to what has been described and illustrated herein, without thereby departing from the scope of the present disclosure.

In particular, it is evident that the detection structure 11 of the microelectromechanical gyroscope 10 of the uniaxial type can be arranged in a horizontal plane to detect the angular velocity around the second horizontal axis y (instead of around the first horizontal axis x), in a manner entirely similar to that previously discussed (in this case, only the third and fourth detection portions 12c,12d of moving mass and the coupled third and fourth stator elements 28c,28d are present).

Some features of the detection structure 11 may also be changed without substantial modification of the proposed solution. For example, as already indicated above, it is possible to provide different shapes of stator elements 28a-28d and of frame 15 of movable mass 12 in horizontal plane xy.

A microelectromechanical gyroscope (10) with a detection structure (11) can be summarized as including a substrate (14) having a top surface (14 a) parallel to a horizontal plane (xy); a movable mass (12) suspended above the substrate (14) and configured to vary according to a first angular velocity (Ω) about a first axis (x) of said horizontal plane (xy) _x ) To perform at least one first detected movement of rotation about a second axis (y) of said horizontal plane; and first and second stator elements (28 a,28 b) fixed to the substrate (14) and arranged below the moving mass (12) to define a capacitive coupling with the moving mass (12), the capacitance value of which is indicative of the first angular velocity (Ω _x ) Wherein the detection structure (11) comprises a single mechanical anchoring structure (20), the single mechanical anchoring structure (20) being used for moving the movement-both a block (12) and the stator elements (28 a,28 b) are anchored to the substrate (14), the single mechanical anchoring structure (20) being arranged internally with respect to the moving block (12) in the horizontal plane (xy); -the movable mass (12) is coupled to the single mechanical anchoring structure (20) by means of coupling elastic elements (18), creating a torsion around the second axis (y); and the stator elements (28 a,28 b) are integrally coupled to the single mechanical anchoring structure (20) in a suspended arrangement above the top surface (14 a) of the substrate (14).

The moving block (12) may include a frame (15) defining a window (16) therein and first and second detection portions (12 a,12 b), the first and second detection portions (12 a,12 b) extending inwardly from the frame (15) to the window (16) and being suspended relative to the substrate (14); and said stator elements (28 a,28 b) may comprise corresponding detection portions (29 a,29 b) arranged to be suspended above a top surface (14 a) of the substrate (14), facing under corresponding detection portions (12 a,12 b) of the movable mass (12), to form corresponding detection capacitors.

The gyroscope may comprise first and a second structural layers (L1, L2) overlapping each other and arranged above said substrate (14); wherein the first and second detection portions (12 a,12 b) of the moving block (22) may be formed in the second structural layer (L2) arranged at a larger distance with respect to the top surface (14 a) of the substrate (14); and the stator elements (28 a,28 b) may be formed in the first structural layer (L1) arranged at a smaller distance with respect to the top surface (14 a) of the substrate (14).

Said stator element (28 a,28 b) may further comprise a respective connecting portion (30 a,30 b) interposed between the respective detecting portion (29 a,29 b) and the single anchoring structure (20) in the horizontal plane xy; wherein the connection portions (30 a,30 b) may be integrally coupled to an overlying top portion (20 a) of the single anchoring structure (20) provided in the second structural layer (L2) by respective dielectric regions (32), the dielectric regions (32) being interposed in a contacting manner between facing surfaces of the connection portions (30 a,30 b) and facing surfaces of the overlying top portion (20 a) of the single anchoring structure (20).

The single anchoring structure (20) may further comprise a bottom (20 b) provided in the first structural layer (L1), the bottom (20 b) being integrally coupled to the top (20 a) and mechanically and electrically coupled to a rotor connection conductive element (R) arranged on the top surface (14 a) of the substrate (14); the connecting portion (30 a,30 b) of the stator element (28 a,28 b) is separated from the bottom portion (20 b) in the horizontal plane (xy) by a separation groove (31).

The detection portion (29 a,29 b) of the stator element (28 a,28 b) may face a wall (17) of a frame (15) of the moving mass (12) at a distance in a horizontal plane (xy); wherein the facing surfaces of the detection portions (29 a,29 b) and the frame (15) may have a circular arc shape in a horizontal plane (xy).

The connection portions (30 a,30 b) of the stator elements (28 a,28 b) may be coupled to respective electrical anchors (34) by respective electrical connection elements (35), the electrical anchors (34) being distinct and separate with respect to a single anchoring structure (20), the electrical connection elements (35) being configured to constitute a negligible mechanical coupling.

The electrical connection element (35) may be provided in the second structural layer (L2) and may have a first end mechanically and electrically coupled to an underlying connection portion (30 a,30 b) of the stator element (28 a,28 b) and a second end coupled to a corresponding electrical anchor (34); and the electrical anchors (34) may be mechanically and electrically coupled to respective stator connection conductive elements (S1, S2) disposed on the top surface (14 a) of the substrate (14).

The detection structure (11) may define: the first and second conductive paths for electrical connection of the first and second stator elements (28 a,28 b) may comprise the electrical anchors (34) and respective stator connection conductive elements (S1, S2), respective electrical connection elements (35) and respective connection portions (30 a,30 b); and a third conductive path for electrical connection of the movable mass (12), which may comprise said single anchoring structure (20), the respective rotor connecting conductive elements (R) and said anchoring elastic elements (18).

The first and second structural layers (L1, L2) may be epitaxial silicon layers grown on a top surface (14 a) of the substrate (14) at least partially electrically and/or mechanically decoupled from each other.

The moving mass (12) may further comprise a second angular velocity (Ω) as a second axis (y) around the horizontal plane (xy) _y ) Performs a second detected movement of rotation about a first axis (x) of the horizontal plane (xy); may further comprise third and fourth stator elements (28 c,28 d) suspended above the substrate (14) and below the moving mass (12) and defining a capacitive coupling with the moving mass (12), the capacitance value of which is indicative of the second angular velocity (Ω _y )。

The movable mass (12) may further comprise third and fourth detection portions (12 c,12 d) extending from the frame (15) within the window (16), suspended with respect to the substrate (14), facing the third and fourth stator elements (28 c,28 d), respectively; and the movable mass (12) may be elastically coupled to a single anchoring structure (20) by a further anchoring elastic element (18), creating a torsion around the first horizontal axis (x).

The anchoring elastic element (18) may have a linear extension along a first or second horizontal axis (x, y) of the horizontal plane (xy) and also be curved in the horizontal plane (xy).

The gyroscope may further comprise a first and a second driving mass (22 a,22 b) arranged outside the frame (15) of the moving mass (12) and coupled to the frame (15) by coupling elastic elements (27 a,27 b) so as to bend in the horizontal plane (xy); the drive masses (22 a,22 b) define respective frames, the first drive electrodes (23) being coupled in an interdigitated arrangement to the second drive electrodes (24) inside thereof, the second drive electrodes (24) being fixed and integral with the substrate (14) and being elastically coupled to the substrate (14) to perform a linear translational drive movement in response to the bias of the first and second drive electrodes (23, 24).

The electronic device (40) may be summarized as including a microelectromechanical gyroscope (10) and a sensor coupled to the microelectromechanical gyroscope (10) and configured to receive an indication of the first angular velocity (Ω _x ) A processing unit (44) of the detection signal of (a).

The present solution aims at providing a MEMS gyroscope with improved stability and reduced drift of electrical characteristics with respect to external stimuli, such as thermal variations, or mechanical or environmental stresses or other various types of external stimuli.

The present disclosure relates to a microelectromechanical gyroscope that includes a substrate having a top surface and a movable mass suspended above the substrate. The first stator element and the second stator element are coupled to the movable mass and are located between the movable mass and the top surface of the substrate. A central mechanical anchor structure coupling the movable mass to the substrate, and a resilient element coupling the movable mass to the central mechanical anchor structure.

The various embodiments described above may be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A microelectromechanical gyroscope, comprising:

a substrate having a top surface;

a movable mass suspended above the substrate;

a first stator element and a second stator element suspended between the movable mass and the top surface of the substrate;

a central mechanical anchoring structure coupled to the substrate, the central mechanical anchoring structure comprising a first portion coupled to the substrate, the first portion being located between the first stator element and the second stator element in a first direction, the central mechanical anchoring structure comprising a second portion coupled to the first stator element and the second stator element, the first portion being located between the second portion and the substrate in a second direction, the second direction being transverse to the first direction; and

a resilient element coupling the movable mass to the central mechanical anchoring structure.

2. The gyroscope of claim 1, wherein the movable mass comprises:

a frame having a window; and

a first detection portion and a second detection portion extending from the frame to the window, the first stator element and the second stator element having respective detection portions facing the first detection portion and the second detection portion of the movable mass, respectively.

3. The gyroscope of claim 2, comprising a first structural layer and a second structural layer on top of each other, the first structural layer being a smaller distance from the top surface of the substrate in the second direction than the second structural layer, the first and second detection portions of the movable mass being in the second structural layer, and the first and second stator elements being in the first structural layer.

4. A gyroscope according to claim 3, wherein the first and second stator elements comprise respective connection portions between the respective detection portions of the first and second stator elements and the central mechanical anchoring structure, the connection portions being coupled to the second portion of the central mechanical anchoring structure in the second structural layer by respective dielectric regions.

5. The gyroscope of claim 4, wherein the first portion is in the first structural layer, the first portion being coupled to the second portion and mechanically and electrically coupled to a rotor connecting conductive element on the top surface of the substrate, the connecting portions of the first stator element and the second stator element being separated from the first portion by a trench.

6. The gyroscope of claim 5, wherein the detection portions of the first and second stator elements extend toward a wall of the frame of the movable mass, the wall having a circular arc shape.

7. The gyroscope of claim 5, comprising an electrical connection element in the second structural layer having a first end mechanically and electrically coupled to the connection portions of the first and second stator elements, and a second end connected to a respective electrical anchor mechanically and electrically coupled to a respective stator connection conductive element on the top surface of the substrate.

8. The gyroscope of claim 7, comprising first and second conductive paths for electrical connection of the first and second stator elements, the respective electrical anchors, the respective stator connecting conductive elements, the respective electrical connection elements, and the respective connection portions; and

and a third conductive path for electrical connection of the movable mass, the mechanical anchoring structure, the rotor connecting conductive element and the elastic element.

9. A microelectromechanical device, comprising:

a substrate;

a central anchor, a first portion of the central anchor coupled to the substrate in a central region of the substrate, the central anchor having a second portion opposite the first portion;

a movable mass, comprising:

a first outer edge opposite the second outer edge;

a central opening between the first outer edge and the second outer edge, the central anchor in the central opening, the movable mass coupled with the second portion of the central anchor;

a protrusion extending into the central opening from the first outer edge toward the central anchor, the protrusion having a first end spaced apart from and adjacent the central anchor;

a stator element suspended between the protrusion and the substrate, the stator element coupled to the central anchor by a dielectric region on a first surface of the central anchor facing the substrate;

an electric anchor on the substrate and in the central opening of the movable mass, the electric anchor being coupled to the stator element;

a first resilient element coupling the movable mass to the central anchor in the central opening, the first resilient element extending from the second portion of the central anchor to the movable mass;

A drive mass coupled to the substrate; and

a second elastic element couples the driving mass to the movable mass.

10. The device of claim 9, wherein the movable mass has a first surface facing the substrate, the first surface having a wall facing the central opening, the wall having a concave curvature, the protrusion extending from the wall.

11. The device of claim 10, wherein a first side of the stator element extends toward the wall in the first surface of the movable mass and has substantially the same shape as the wall.

12. The device of claim 11, wherein the first and second elastic elements are separated from each other by the movable mass.

13. The device of claim 12, wherein the second portion of the central anchor includes a first side coupled with the movable mass, the first side being transverse to a second side of the central anchor, the second side facing the protrusion of the movable mass.

14. The device of claim 13, wherein a portion of the stator element is located in the central opening of the movable mass.

15. A microelectromechanical device, comprising:

a substrate;

fixing the mechanical structure;

a movable mass, comprising:

an opening comprising a body aligned with the fixed mechanical structure and a plurality of extensions away from the body;

a first surface opposite a second surface, the first surface of the movable mass facing the substrate, a first side of the movable mass between a first and a second one of the plurality of extensions of the opening, and a second side of the movable mass between a third and a fourth one of the plurality of extensions of the opening; and

a first stator element and a second stator element coupled to the fixed mechanical structure, the first stator element located between the first side of the movable mass and the substrate, and the second stator element located between the second side of the movable mass and the substrate.

16. The device of claim 15, comprising a connecting element coupled between the stator element and an electrical anchor on the substrate, and the connecting element is located in the opening of the movable mass.

17. The device of claim 16, comprising a spring assembly, a first of the spring assemblies coupling the movable mass to the fixed mechanical structure.

18. The device of claim 17, comprising a drive mass coupled to the movable mass via a second one of the elastic assemblies, the drive mass being located at an opposite end of the movable mass.

19. The device of claim 18, wherein the drive mass comprises first and second drive electrodes secured to the substrate, the first and second drive electrodes being adjacent to each other in a pattern.

20. The device of claim 19, wherein the drive mass is elastically coupled to the substrate via a folded elastic element.