CN217808767U

CN217808767U - Combined micro-electromechanical device

Info

Publication number: CN217808767U
Application number: CN202221280850.8U
Authority: CN
Inventors: F·韦尔切西; L·塞吉齐; L·奥吉欧尼; L·科索
Original assignee: STMicroelectronics SRL
Current assignee: STMicroelectronics SRL
Priority date: 2021-05-26
Filing date: 2022-05-25
Publication date: 2022-11-15
Anticipated expiration: 2032-05-25
Also published as: CN115403001A

Abstract

Embodiments of the present disclosure generally relate to composite microelectromechanical devices. A method for fabricating a composite microelectromechanical device includes: forming at least a first microelectromechanical structure and a second microelectromechanical structure in a die of semiconductor material; performing a first bonding stage to bond the cover to the die via a bonding area or adhesive to define at least a first cavity and a second cavity at the first microelectromechanical structure and the second microelectromechanical structure, respectively, the cavities being under controlled pressure; forming an access passage through the cover in fluid communication with the first chamber for controlling pressure values in the first chamber in different ways with respect to corresponding pressure values in the second chamber; and performing a second bonding stage, after which the bonding area is deformed to hermetically close the first cavity with respect to the access passage. An embodiment of the utility model provides a combination micro electromechanical device that the cost of manufacture is cheap.

Description

Combined micro-electromechanical device

Technical Field

The present disclosure relates to a combined micro-electromechanical device.

Background

Composite MEMS devices are known and may include two microelectromechanical structures on the same substrate. The microelectromechanical structures of known composite MEMS devices may depend on different operating conditions, in particular with respect to different values of pressure within the respective structures. For example, the pressure in one structure may be greater than the pressure in another structure.

The above-mentioned need to define different pressure values within the corresponding structures in the combined MEMS device poses some implementation problems to the manufacturing process.

In this regard, a first known solution provides the use of a getter area which is introduced into one of the above-mentioned structures in order to regulate the pressure inside the same structure in a desired manner.

A second known solution (described in, for example, US 10,017,380B1 or US 9,919,919 B2) provides for the definition of a "chimney" or access passage through the structure at the location where the pressure needs to be regulated.

However, both of the above known solutions have drawbacks and have common problems associated with the difficulty of controlling process extensions and pressure set points and the complexity of the manufacturing process.

In particular, in the case of the first solution, the final pressure value at the location where the getter area is formed is affected by a series of factors including the tolerance of the pressure set point in the other chamber, the composition and concentration of the process gas, the activation of the getter and the ability to reduce the pressure inside the chamber.

Furthermore, integrating the getter area into the manufacturing process flow increases the manufacturing complexity of the device.

In the case of the second solution, the hermetic closure of the access passage in order to maintain the pressure requires complex additional operations, in particular with respect to laser melting, which require an increase in the cost and time of the manufacturing process.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present invention is directed to a combined micro-electro-mechanical device.

According to one or more aspects of the present disclosure, there is provided a combined microelectromechanical device, including: a first microelectromechanical structure on the die; a second microelectromechanical structure on the die; a lid coupled to the die; an adhesive between the lid and the die, the adhesive including a first adhesive portion; a first cavity corresponding to the first microelectromechanical structure, the first cavity having a controlled pressure value within the first cavity; a second chamber corresponding to the second microelectromechanical structure, the second chamber having a controlled pressure value within the second chamber that is different from the controlled pressure value within the first chamber; and an access passage through the cover proximate to the first cavity, the first cavity being hermetically sealed with respect to the access passage, the access passage having a first end open to the external environment and a second end opposite the first end, the second end of the access passage being sealed by a first adhesive portion of the adhesive.

In one or more embodiments, the first adhesive portion of the adhesive extends laterally across the access channel and extends beyond the access channel toward the first cavity.

In one or more embodiments, the first adhesive part of the adhesive is arranged externally and proximate to the first microelectromechanical structure with respect to the first microelectromechanical structure, and wherein the adhesive further comprises a second adhesive part arranged externally and proximate to the second microelectromechanical structure with respect to the second microelectromechanical structure, and a third adhesive part arranged at a separate part of the die between the first microelectromechanical structure and the second microelectromechanical structure, and wherein the first cavity is laterally bounded by the first adhesive part and the third adhesive part of the adhesive and comprises a first recess in a die-facing surface of the cover, and the second cavity is laterally bounded by the second adhesive part and the third adhesive part of the adhesive and comprises a second recess in a die-facing surface of the cover.

In one or more embodiments, the first microelectromechanical structure is a gyroscope and the second microelectromechanical structure is an accelerometer, and wherein a controlled pressure value in a first cavity associated with the gyroscope is less than a controlled pressure value in a second cavity associated with the accelerometer.

In one or more embodiments, the binder is a frit material.

In one or more embodiments, the access channel is arranged laterally with respect to the first microelectromechanical structure and externally with respect to the first microelectromechanical structure.

According to one or more aspects of the present disclosure, there is provided a combined micro-electromechanical device including: a first microelectromechanical structure on the die; a second microelectromechanical structure on the die; a lid coupled to the die; an adhesive between the lid and the die, the adhesive including a first adhesive portion, a second adhesive portion, and a third adhesive portion; a first cavity defined at least in part by the cover, the first adhesive portion, and the third adhesive portion, the first cavity corresponding to the first microelectromechanical structure and having a first pressure value within the first cavity; a second cavity defined at least in part by the cover, the second adhesive portion, and the third adhesive portion, the second cavity corresponding to the second microelectromechanical structure and having a second pressure value within the second cavity that is different from the first pressure value; and an access passage through the cap, the first and second cavities each hermetically sealed about the access passage, the access passage having a first open end and a second end opposite the first end, the second end of the access passage sealed by one of the first and second adhesive portions of the adhesive.

In one or more embodiments, the access channel is proximate to the first cavity, wherein the second end of the access channel is sealed by the first adhesive portion of the adhesive.

In one or more embodiments, the second end of the access channel is sealed by a first adhesive portion that extends laterally across and beyond the second end of the access channel and terminates prior to the first lumen.

In one or more embodiments, the first microelectromechanical structure is a gyroscope and the second microelectromechanical structure is an accelerometer, the first pressure value being less than the second pressure value.

In one or more embodiments, the lid includes a first recess and a second recess in a die-facing surface of the lid, the first cavity being at least partially defined by the first recess and the second cavity being at least partially defined by the second recess.

By using embodiments according to the present disclosure, at least part of the aforementioned problems may be solved and corresponding effects achieved, such as providing a combined microelectromechanical device that is inexpensive to manufacture.

Drawings

For a better understanding of the present solution, preferred embodiments thereof are now described, by way of non-limiting example only, and with reference to the accompanying drawings, in which:

FIGS. 1A-1E are schematic cross-sectional views of successive steps in an embodiment of a manufacturing process for a combined microelectromechanical device according to the present disclosure;

FIG. 2 is a schematic cross-sectional view of an embodiment of a composite microelectromechanical device resulting from a manufacturing process according to the present disclosure; and

FIG. 3 is a schematic block diagram of an embodiment of an electronic device including a combined microelectromechanical device of the present disclosure.

Detailed Description

A composite MEMS device according to the present disclosure may include at least first and second microelectromechanical structures, e.g., first and second detection structures defining first and second sensors, arranged in the same semiconductor material die. The use of these combined MEMS devices is particularly advantageous, for example in terms of area occupation and optimization of the electrical connections.

In particular, the combined MEMS device may define an inertial measurement unit, a so-called IMU, comprising a plurality of different sensors in the same semiconductor material die and having a plurality of sensing axes, for example at least one accelerometer and one gyroscope, both of which are triaxial, in order to provide acceleration and angular velocity information of the object or subject to which they are applied.

For example, these devices are widely used in mobile or wearable devices (such as smartphones, tablets, smartwatches, etc.) or in automotive or industrial applications.

The accelerometers and gyroscopes comprise respective movable structures elastically suspended with respect to a common substrate formed in the semiconductor material die and housed in respective closed cavities, typically defined by bonding a lid to the same substrate.

In one or more embodiments, a method for fabricating a composite microelectromechanical device is provided that overcomes the previously highlighted problems of conventional composite MEMS devices.

As shown in fig. 1A, a process for manufacturing a combined microelectromechanical (MEMS) device initially provides for forming a first microelectromechanical structure 2a and a second microelectromechanical structure 2b in a die 1 of semiconductor material, in particular silicon.

The first microelectromechanical structure 2a and the second microelectromechanical structure 2b are formed in a first portion 1' and a second portion 1 ″ of the die 1, respectively, are different from each other and are separated by a separation portion 3. In a non-limiting example, the separation portion 3 may be generally located in the center of the die 1, but the location of the separation portion 3 may be selected based on the size of the

MEMS structures

2a, 2b.

In the embodiment schematically illustrated in fig. 1A, in which the combined MEMS device defines an inertial measurement unit, the first microelectromechanical structure 2a is a detection structure defining a capacitive gyroscope, for example of the triaxial type; while the second microelectromechanical structure 2b is a detection structure defining a capacitive accelerometer, for example also of the triaxial type.

Specifically, the die 1 includes a substrate 4 having a top surface 4a, with a dielectric layer 5 formed on the top surface 4 a; the aforementioned first and second

microelectromechanical structures

2a, 2b are formed above the top surface 4a of the substrate 4.

In the embodiment shown, the first microelectromechanical structure 2a and the second microelectromechanical structure 2b comprise respective suspension elements, schematically indicated with 7 (for example inertial mass, detection and/or actuation electrodes, elastic elements), defined in the same structural layer 6 above the substrate 4; these suspension elements 7 are coupled to respective anchoring elements 8, the anchoring elements 8 being integral with respect to the substrate 4, also defined starting from the same structural layer 6.

Furthermore, a conductive layer 9, for example of polycrystalline silicon, is arranged and suitably shaped on the dielectric layer 5 so as to define suitable electrical connections between the first and second

microelectromechanical structures

2a, 2b and contact pads accessible from outside the combined microelectromechanical device (in a manner not illustrated here), for example for biasing of the same structures and acquisition of corresponding detection signals.

In the example shown, the aforementioned separate portion 3 of the die 1 comprises a portion of the structural layer 6 interposed between the respective anchoring elements 8 of the first and second

microelectromechanical structures

2a, 2b. In fig. 1A, the separation portion 3 may correspond to a central portion of the anchoring element 8 positioned between the first microelectromechanical structure 2a and the second microelectromechanical structure 2b.

The manufacturing process also provides for bonding of the lid 10 over the structural layer 6 of the die 1, as shown in fig. 1B.

The cover 10 is treated so as to define a first recess 12a and a second recess 12b in the surface 11 of the same cover 10 facing the structural layer 6 of the die 1. The surface 11 may also be referred to herein as the engagement surface 11 of the cover 10.

In particular, the first recess 12a is placed at the first detection structure 2a, while the second recess 12b is placed at the second detection structure 2b.

A bonding region 14 of a suitable material for ensuring an airtight bond, in particular a glass frit material, which may also be referred to herein as an adhesive 14, is bonded to the engagement face 11 of the cover 10 to couple the cover 10 to the structural layer 6.

In particular, the bonding region 14 comprises a first bonding portion 14a and a second bonding portion 14b (which may also be referred to herein as first adhesive portion 14a and second adhesive portion 14 b) (similar to the first portion 1' and second portion 1 ″ of the die 1, respectively) arranged externally and in proximity to the first detection structure 2a and the second detection structure 2b, respectively; and a third bonding portion 14c (which may also be referred to herein as a third adhesive portion 14 c) disposed at the above-described separation portion 3 of the same die 1. The third bonding portion 14c is interposed between the first bonding portion 14a and the second bonding portion 14b along a first horizontal axis X including a horizontal plane XY of the bonding face 11.

In one embodiment, the bonding region 14 may define a ring around the first and second recesses 12a, 12B in the horizontal plane XY, in which case the first and third bonding

portions

14a, 14c and the second and third bonding portions 14B, 14c are connected to each other (in a manner not shown in fig. 1B).

The bonding region 14 has a first or initial height h along the vertical axis Z ₁ The vertical axis Z is perpendicular to the engagement surface 11 of the cover 10 lying in the horizontal plane XY. As shown in FIG. 1b, in some embodiments, the first height h ₁ Between the structural layer 6 and the joint face 11 of the cover 10.

As shown in fig. 1B, a spacer or stop element (so-called "stop") 16 may be coupled to the same engagement face 11 of the lid 10, for example a first engagement portion 14a close to the engagement area 14, the first engagement portion 14a having a smaller initial height h with respect to the engagement face 11 than the aforementioned one ₁ Second or separation height h _s 。

The stop element 16 may be integral with the cover 10 and defined at the same time as the above-mentioned first and

second recesses

12a, 12b are defined. The stop element 16 may also be referred to herein as extending a separation height h from the engagement surface 11 of the lid _s A protrusion 16 or a projection 16.

As previously illustrated in fig. 1B and with reference to fig. 1C, when the cover 10 is placed in contact with the die 1, the bonding area 14 is in contact with the structural layer 6 of the same die 1, defining the following interposed between the same structural layer 6 and the bonding face 11 of the cover 10: a first cavity 20a, arranged at the first microelectromechanical structure 2a, laterally delimited (in the direction of the above-mentioned first horizontal axis X) by a first bonding portion 14a and a third bonding portion 14c of the bonding area 14, and comprising a first recess 12a of the cover 10; and a second cavity 20b arranged at the second microelectromechanical structure 2b, laterally delimited by a second bonding portion 14b and a third bonding portion 14c of the same bonding area 14, and comprising the second recess 12b of the aforementioned cover 10.

As shown in FIG. 1C, a first bonding stage (by thermocompression) is then performed, wherein the processing environment is at a first value P ₁ At a controlled pressure of (1), a first value P ₁ For example corresponding to a desired operating pressure of the second microelectromechanical structure 2b (in this embodiment, a higher pressure suitable for the operation of the accelerometer, for example of the order of a few tens of mBar, for example equal to 100 mBar).

Due to the first pressure P ₁ Reflow of the bonding material under, in particular the frit, which first bonding stage requires a deformation, in particular a flattening or "pinching" (height reduction and widening), of the bonding region 14; thus, the bonded region 14 exhibits less than the initial height h ₁ Middle or third height h of ₂ 。

In the embodiment shown, this intermediate height h ₂ Corresponding to the separation height h of the stop element 16 _s In this case, it practically defines the separation distance between the lid 10 and the structural layer 6 of the die 1 at the end of the first bonding stage described above. In other words, the pressure P ₁ The separation element 16 is brought into contact with the structural layer 6, as shown in fig. 1C, so that the height of the bonding region 14 is from the initial height h in fig. 1B ₁ Reduced and widened to a separation height h _s 。

As shown in fig. 1D, the manufacturing process provides the possibility of thinning the lid 10 starting from the outer surface 11' opposite the engagement surface 11. Subsequently, starting from the outer surface 11' (possibly resulting from a thinning operation or from a separate and distinct operation) and close to the first joining portion 14a of the joining region 14, an etching is performed on the same lid 10, internally with respect to the arrangement of the first recess 12 a. Etching may be performed on the cover 10 between the first bonding region 14a and the first recess 12 a.

This etching results in the definition of an access channel 22, the access channel 22 extending completely through the cover 10 (from the outer surface 11' to the engagement surface 11) so as to be in fluid communication with the first cavity 20a. In one embodiment, the access channel 22 may extend through the cover 10 in fluid communication with the second cavity 20b instead of the first cavity 20a, with a corresponding aspect of the device (i.e., the anchor 8, etc.) adapted to receive the access channel 22 adjacent the second cavity 20 b. In such embodiments, the manufacturing process and the final composite microelectromechanical device 30 may generally be the same as the processes and devices described herein, except that the access channels 22 are formed on the other side of the device 30 that is sealed by the second adhesive portion 14 b.

In the case where the stop element 16 has been previously formed, the etching is performed at this stop element 16, so that the same stop element 16 is completely removed after the etching.

As previously shown in fig. 1D, the etching may continue through a surface portion of the structural layer 6 of the die 1 in case, as in the example shown, no etch stop layer has previously been formed, resulting in the formation of an indentation 25 vertically at the above-mentioned channel 22.

The pressure in the first chamber 20a is then regulated in a suitable manner by the inlet channel 22, for example by a gas flow having the desired pressure. The second cavity 20b is hermetically sealed by the second and

third bonding areas

14b, 14c and the additional structure of the combined MEMS device, so that the second cavity 20b maintains a higher pressure from the previous manufacturing step and is not affected by the regulation of the pressure in the first cavity 20a by the access channel 22.

As shown in fig. 1E, then has a second value P ₂ Is performed under a controlled pressure, a second value P ₂ For example corresponding to a desired operating pressure of the first microelectromechanical structure 2 a. In one embodiment, the second value P ₂ Is less than a first value P ₁ And corresponds to a lower pressure suitable for the operation of the gyroscope, for example of the order of a few mBar, for example equal to 1mBar. However, in some embodiments, the second pressure P ₂ Is equal to or greater than the first pressure P ₁ Depending on the desired operating conditions of the

microelectromechanical structure

2a, 2b.

This second bonding stage requires further deformation, in particular by planarization or pressing (height reduction and widening) of the bonding region 14, due to reflow of the bonding material. As a result of the second bonding stage in fig. 1E, the bonding region 14 exhibits a fourth or final height h between the lid 10 and the structural layer 6 of the die 1 ₃ The fourth or final height h ₃ Less than the intermediate height h ₂ . Final heightDegree h ₃ Less than the intermediate height h ₂ Since the stop element 16 was removed in a preceding process step and no longer prevents the cover 10 from being moved to a specific separation height h _s Closer to the structural layer 6. Although deforming the bonding area 14, the second bonding stage does not affect the pressure in the second cavity 20b, the second cavity 20b remaining hermetically sealed during the second bonding stage. In some embodiments, reducing the volume of the second cavity 20b from the second bonding stage via planarization of the bonding region 14 may produce a negligible increase in pressure in the second cavity 20b, although any increase is not expected to affect the operation of the combined MEMS device.

In particular, according to a particular aspect of the present solution, the joining zone 14 (more particularly, the corresponding first joining portion 14 a) extends laterally below the access channel 22 and beyond the same access channel 22 towards the first cavity 20a, closing the access channel 22 at the bottom and at the second pressure P ₂ The same first chamber 20a is hermetically sealed with respect to the external environment. Thus, in the second bonding stage, the same first bonding area 14a is reflowed to extend beyond and seal the access passage 22. In one embodiment, the first bonding region 14a terminates before reaching the first cavity 20a to prevent the first bonding region 14a from interfering with the operation of the first microelectromechanical structure 2 a. The extent of the first bonding region 14a during the bonding stage can be controlled depending on various factors including, but not limited to, the amount and type of bonding material, the pressure during each bonding stage, and the length of time of each bonding stage.

In summary, at the end of the above-mentioned second bonding phase, a final combined MEMS device (COMBO MEMS) 30 is thus obtained as shown in fig. 2 (it should be noted that in this fig. 2, the indentation 25 is not shown, by way of example).

Thus, in this combined MEMS device 30, advantageously a first microelectromechanical structure 2a and a second microelectromechanical structure 2b are provided, the respective first cavity 20a and second cavity 20b being hermetically closed and respectively set to a first pressure P ₁ And a second pressure P ₂ With different values optimized for the respective operations of the same first and second

microelectromechanical structures

2a, 2b.

In particular, in the combined MEMS device 30, the access passage 22 is provided through the cover 10, arranged laterally outside with respect to the first microelectromechanical structure 2a, the first end 22a being open to the outside of the combined MEMS device 30, and the second end 22b, opposite the first end 22a, along the vertical axis Z, being closed by a first bonding portion 14a of the bonding area 14, the first bonding portion 14a bonding the cover 10 to the die 1, wherein identical first and second

microelectromechanical structures

2a, 2b are formed.

In other words, the aforesaid first coupling portion 14a of the coupling zone 14 therefore extends under the cover 10 so as to extend beyond the aforesaid access channel 22, towards the first cavity 20a.

The advantages of the present solution are clear from the foregoing description.

In any case, it is emphasized that the present solution is cheap to manufacture, since it does not use additional complex and expensive process steps to obtain a closed cavity at different pressures of the microelectromechanical structure of the combined MEMS device.

As discussed in detail previously, the present solution provides a bonding process (in particular by frit bonding) that is divided into two distinct stages. The first stage of the bonding process provides a bonding cap and a sensor die with a controlled final thickness of bonding area therebetween (which can be achieved by controlling the amount of bonding material and/or bonding pressure and/or using stop elements). The second phase of the bonding process is performed after defining the access channel at one of the cavities (for example, one of the gyroscopes), to allow controlling the pressure in that cavity and to provide an airtight closure of the access channel at the end of the same second phase, using the same bonding material (closing the opening of the access channel at the bottom due to its flattening).

It is therefore emphasized that the process uses a single bonding process (divided into two distinct stages), and therefore does not require the special or additional processing associated with conventional composite MEMS devices.

The solution in question is advantageously applied to electronic devices, for example of the portable type (such as smartphones, tablets, smartwatches), as schematically shown in figure 3.

The electronic device denoted by 40 therefore comprises: a combined MEMS device 30, the combined MEMS device 30 for example serving as an inertial measurement unit; and a control unit 42, the control unit 42 being operatively coupled to the combined MEMS device 30 and configured to receive detection signals provided by the same combined MEMS device 30 for controlling the general operation of the electronic apparatus 40.

Finally, it is clear that modifications and variations can be made to what has been described and illustrated, without thereby departing from the scope of the present invention, as defined in the appended claims.

It is particularly emphasized that the solution in question may find advantageous application in all MEMS devices having at least two structures with respective different closed cavities, where different pressure values are advantageous (for example, in the case of a combined MEMS device comprising two accelerometers or two gyroscopes or any other closed cavity structure, such as a microphone or a pressure sensor).

Furthermore, in a possible embodiment, the first value P of the controlled pressure in the first bonding stage ₁ May alternatively be greater than the second value P of the controlled pressure in the second joining phase ₂ (in the case where the pressure in the first chamber 20a should be lower than the pressure in the second chamber 20 b).

As previously mentioned, it is again emphasized that the stop element 16 may not be used in the manufacturing process, for example in case the thickness of the bonding area 14 is only controlled by controlling the amount of material and/or the bonding pressure.

Furthermore, the etching used to form the access channel 22 may not result in the definition of the indentation 25 (and therefore it does not appear in the final MEMS device, as shown on the other hand in the example of fig. 2), for example under the same access channel 22, in the previous case of defining an etch stop layer on the surface of the structural layer 6 facing the cap 10.

One or more embodiments of a method for fabricating a composite microelectromechanical device (30) may be summarized as including: forming at least a first microelectromechanical structure (2 a) and a second microelectromechanical structure (2 b) in a die (1) of semiconductor material; the cover is connected by a connecting region (14)(10) Is bonded to the die (1) so as to define at least a first cavity (20 a) and a second cavity (20 b) at the first microelectromechanical structure and at the second microelectromechanical structure, respectively; -forming an inlet channel (22) through said cover (10) in fluid communication with the first chamber (20 a) for controlling the pressure value inside said first chamber (20 a) in a different manner with respect to the corresponding pressure value inside said second chamber (20 b); -closing said first chamber (20 a) hermetically with respect to said inlet passage (22), the coupling comprising having a first value (P) before forming said inlet passage (22) ₁ ) Under a controlled pressure of (a) to achieve a first binding phase, a first value (P) ₁ ) Is a function of the pressure value in said second chamber (20 b) and, after the formation of said inlet channel (22), has a second value (P) ₂ ) Is carried out at a corresponding controlled pressure, a second value (P) ₂ ) Is a function of the value of the pressure inside said first chamber (20 a), wherein, as a result of said second coupling phase, the coupling zone (14) deforms so as to hermetically close said first chamber (20 a) with respect to said inlet passage (22).

The method may further comprise: the first bonding stage comprises the extrusion of a bonding area (14), the bonding area (14) exhibiting a median height (h) ₂ ) The intermediate height (h) ₂ ) Less than the initial height (h) ₁ ) (ii) a And the above-mentioned second bonding stage may require further pressing of the bonding area (14), the bonding area (14) exhibiting a final height (h) ₃ ) The final height (h) ₃ ) Less than the above-mentioned intermediate height (h) ₂ ) And further extends laterally below the access passage (22) and beyond the access passage (22) towards the first chamber (20 a), closing the access passage (22) at the bottom and hermetically sealing said first chamber (20 a).

The method may further comprise: the bonding region (14) comprises a first bonding portion (14 a), the first bonding portion (14 a) being arranged externally with respect to the first detection structure (2 a) and close to the first detection structure (2 a), and the forming of the access passage (22) through said cover (10) may comprise performing an etching over the entire thickness of the cover (10) close to said first bonding portion (14 a); and the second bonding stage requires further pressing of the first bonding portion (14 a) to hermetically close the first cavity (20 a).

The method may further comprise: the cover (10) comprises a spacer element (16), the spacer element (16) extending from a bonding face (11) of the cover (10) facing the die (1) towards said die (1), being arranged close to a first bonding portion (14 a) of the bonding area (14), and having a separation height (h) _s ) (ii) a And, in the first bonding stage, the spacer element (16) determines the median height (h) of the bonding area (14) ₂ ) The above-mentioned intermediate height (h) ₂ ) Equal to the above separation height (h) _s )。

The method may further comprise: -etching for forming said access passages (22) to completely remove said spacer elements (16); etching stops in the structural layer (6) of the die (1) facing the lid (10) to form an indentation (25) therein; the bonding region (14) comprises a frit material; the first microelectromechanical structure (2 a) defines a gyroscopic sensor and the second microelectromechanical structure (2 b) defines an acceleration sensor; wherein the above-mentioned first value (P) corresponding to the controlled pressure in the first cavity (20 a) associated with the gyroscopic sensor ₁ ) May be lower than the above-mentioned second value (P) corresponding to the controlled pressure in the second chamber (20 b) associated with the acceleration sensor ₂ )。

The method may further comprise: the binding region (14) comprises: a first binding portion (14 a) and a second binding portion (14 b) arranged externally and in proximity to the first detection structure (2 a) and the second detection structure (2 b), respectively, with respect to the first detection structure (2 a) and the second detection structure (2 b); and a third bonding portion (14 c) arranged at the separation portion (3) of the die (1), the separation portion (3) separating the first and second detection structures; and wherein said first cavity (20 a) may be laterally delimited by first and third joining portions (14 a, 14 c) of the joining area (14) and may comprise a first recess (12 a) formed in the cover (10) starting from the joining face (11) facing said die (1); and the aforementioned second cavity (20 b) may be laterally delimited by the second and third joining portions (14 b, 14 c) of the joining area (14) and may comprise a second recess (12 b) formed in the cover (10) starting from the aforementioned joining face (11) facing the die (1). .

A combined microelectromechanical device (30) may be summarized as including: a die (1) of semiconductor material housing at least a first microelectromechanical structure (2 a) and a second microelectromechanical structure (2 b); a cover (10) bonded to the die (1) by means of a bonding area (14) and defining at least a first cavity (20 a) and a second cavity (20 b) at the first microelectromechanical structure and at the second microelectromechanical structure, respectively, wherein the first cavity (20 a) has a controlled pressure value therein that is different from a corresponding controlled pressure value within the second cavity (20 b); and an access passage (22) through the lid (10) proximate to the first cavity (20 a), the first cavity (20 a) being hermetically closed about the access passage (22), the access passage (22) having a first end (22 a) open to an environment external to the combined MEMS device (30) and a second end (22 b) opposite the first end (22 a), the second end (22 b) being closed by a first bonding portion (14 a) of the bonding region (14).

The device may further comprise: a first joining portion (14 a) of the joining area (14) extends laterally under the access passage (22) and beyond the same access passage (22) towards the first chamber (20 a), closing the access passage (22) at the bottom and hermetically sealing said first chamber (20 a); and the first binding portion (14 a) of the above-mentioned binding area (14) is arranged externally with respect to the first detection structure (2 a) and close to the first detection structure (2 a); and the bonding region (14) may further include: with respect to a second bonding portion (14 b) of the second detection structure (2 b) arranged externally and close to the second detection structure (2 b), and a third bonding portion (14 c) arranged at a separation portion (3) of the die (1), the separation portion (3) separates the above-mentioned first detection structure from the above-mentioned second detection structure; and said first cavity (20 a) may be laterally delimited by first and third joining portions (14 a, 14 c) of the joining area (14) and may comprise a first recess (12 a) formed in the cover (10) starting from the joining face (11) facing said die (1); and the aforementioned second cavity (20 b) may be laterally delimited by the second and third joining portions (14 b, 14 c) of the joining area (14) and may comprise a second recess (12 b) formed in the cover (10) starting from the aforementioned joining face (11) facing the die (1).

The device may further comprise: a first microelectromechanical structure (2 a)) -defining a gyroscopic sensor and the above-mentioned second microelectromechanical structure (2 b) defines an acceleration sensor; wherein the controlled pressure in the first chamber (20 a) associated with the gyrosensor has a first value (P) ₁ ) The first value (P) ₁ ) A second value (P) lower than the controlled pressure in a second chamber (20 b) associated with the acceleration sensor ₂ ) (ii) a The bonding region (14) comprises a frit material; and the access channel (22) is arranged laterally outside with respect to the first microelectromechanical structure (2 a).

One or more embodiments of an electronic device (40) may be summarized as including a combined microelectromechanical device (30) and a control unit (42) operatively coupled to the combined microelectromechanical device (30).

One or more embodiments of a combined micro-electromechanical device can be summarized as including: a first microelectromechanical structure on the die; a second microelectromechanical structure on the die; a lid coupled to the die; an adhesive between the lid and the die, the adhesive including a first adhesive portion, a second adhesive portion, and a third adhesive portion; a first cavity defined at least in part by the cover, the first adhesive portion, and the third adhesive portion, the first cavity corresponding to the first microelectromechanical structure and having a first value of pressure within the first cavity; a second cavity defined at least in part by the cover, the second adhesive portion, and the third adhesive portion, the second cavity corresponding to the second microelectromechanical structure and having a second pressure value within the second cavity that is different from the first pressure value; and an access passage through the cap, the first and second cavities both being hermetically sealed with respect to the access passage, the access passage having a first open end and a second end opposite the first end, the second end of the access passage being sealed by one of the first and second adhesive portions of the adhesive.

The combined microelectromechanical device may further include: the access channel is proximate to the first cavity, wherein a second end of the access channel is sealed by a first adhesive portion of the adhesive; the second end of the access channel is sealed by a first adhesive portion that extends laterally across and beyond the second end of the access channel and terminates before the first lumen; the first micro-electromechanical structure is a gyroscope and the second micro-electromechanical structure is an accelerometer, and the first pressure value is smaller than the second pressure value; and the lid includes a first recess and a second recess in a die-facing surface of the lid, the first cavity being at least partially defined by the first recess and the second cavity being at least partially defined by the second recess.

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. 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 disclosure.

Claims

1. A composite microelectromechanical device, comprising:

a first microelectromechanical structure on the die;

a second microelectromechanical structure on the die;

a lid coupled to the die;

an adhesive between the lid and the die, the adhesive comprising a first adhesive portion;

a first cavity corresponding to the first microelectromechanical structure, the first cavity having a controlled pressure value within the first cavity;

a second cavity corresponding to the second microelectromechanical structure, the second cavity having a controlled pressure value within the second cavity that is different from the controlled pressure value within the first cavity; and

an access passage through the cover proximate the first chamber,

the first chamber is hermetically sealed with respect to the access passage,

the access channel has a first end open to an external environment and a second end opposite the first end, the second end of the access channel being sealed by the first adhesive portion of the adhesive.

2. The composite microelectromechanical device of claim 1, characterized in that the first adhesive portion of the adhesive extends laterally across the access channel and beyond the access channel towards the first cavity.

3. The combined microelectromechanical device of claim 1, characterized in that the first adhesive part of the adhesive is arranged externally and close to the first microelectromechanical structure with respect to the first microelectromechanical structure, and

wherein the adhesive further comprises a second adhesive portion arranged externally with respect to and in proximity to the second microelectromechanical structure and a third adhesive portion arranged at a separate portion of the die between the first and second microelectromechanical structures, and

wherein the first cavity is laterally bounded by the first and third adhesive portions of the adhesive and includes a first recess in a surface of the cover facing the die, and the second cavity is laterally bounded by the second and third adhesive portions of the adhesive and includes a second recess in the surface of the cover facing the die.

4. The combined microelectromechanical device of claim 1, characterized in that the first microelectromechanical structure is a gyroscope and the second microelectromechanical structure is an accelerometer, and

wherein a controlled pressure value in the first cavity associated with the gyroscope is less than a controlled pressure value in the second cavity associated with the accelerometer.

5. The composite microelectromechanical device of claim 1, characterized in that the adhesive is a frit material.

6. Combined microelectromechanical device of claim 1, characterized in that the access channel is arranged laterally with respect to the first microelectromechanical structure and externally with respect to the first microelectromechanical structure.

7. A composite microelectromechanical device, comprising:

a first microelectromechanical structure on the die;

a second microelectromechanical structure on the die;

a lid coupled to the die;

an adhesive between the lid and the die, the adhesive comprising a first adhesive portion, a second adhesive portion, and a third adhesive portion;

a first cavity defined at least in part by the cover, the first adhesive portion, and the third adhesive portion, the first cavity corresponding to the first microelectromechanical structure and having a first pressure value within the first cavity;

a second cavity defined at least in part by the cover, the second adhesive portion, and the third adhesive portion, the second cavity corresponding to the second microelectromechanical structure and having a second pressure value within the second cavity that is different from the first pressure value; and

an access passage through the cover, the first and second chambers each being hermetically sealed about the access passage,

the access channel has a first open end and a second end opposite the first end, the second end of the access channel being sealed by one of the first and second adhesive portions of the adhesive.

8. The composite microelectromechanical device of claim 7, characterized in that the access channel is proximate to the first cavity, wherein the second end of the access channel is sealed by the first adhesive portion of the adhesive.

9. The composite microelectromechanical device of claim 7, characterized in that the second end of the access channel is sealed by the first adhesive portion that extends laterally across and beyond the second end of the access channel and terminates before the first cavity.

10. The combined microelectromechanical device of claim 7, characterized in that the first microelectromechanical structure is a gyroscope and the second microelectromechanical structure is an accelerometer, the first pressure value being smaller than the second pressure value.

11. The composite microelectromechanical device of claim 7, characterized in that the cover comprises a first recess and a second recess in a surface of the cover facing the die, the first cavity being at least partially defined by the first recess and the second cavity being at least partially defined by the second recess.