Process for manufacturing combined micro-electro-mechanical device and corresponding combined micro-electro-mechanical device

Abstract

The invention relates to a process for manufacturing a combined micro-electro-mechanical device and a corresponding combined micro-electro-mechanical device. A process for manufacturing a combined micro-electro-mechanical device envisages: forming at least a first micro-electro-mechanical structure and a second micro-electro-mechanical structure in a sensor wafer at a major surface; forming at least a first cavity and a second cavity in the capping wafer at the respective major surfaces; an air suction area is formed in the first cavity; the main surfaces of the sensor wafer and the capping wafer are bonded through a bonding region, thereby defining a first sealing environment and a second sealing environment for the micro-electro-mechanical structure at different pressure values. Before the bonding step, a raised frame is formed in a manner to be positioned around the first cavity; the bonding region determines to bond the sensor wafer and the capping wafer at the raised frame and defines a first sealed environment associated with the first cavity within a time interval prior to sealed closure of the second cavity.

Description

Technical Field

[0001] The present solution relates to a process for manufacturing a microelectromechanical (manufactured using MEMS - Micro Electro Mechanical Systems - technology) combined device, a so-called "combo", with reduced crosstalk; the present solution also relates to a corresponding combined microelectromechanical device. Background Art

[0002] Combined MEMS devices are known, i.e. comprising at least first and second microelectromechanical structures, e.g. first and second sensing structures defining first and second sensors, which sensing structures are arranged in the same semiconductor material die, typically side by side at the level of the main extension of the same die.

[0003] Using a combined MEMS device is particularly advantageous, for example in terms of optimization of area occupation and electrical connections (compared to the case where separate sensors are manufactured in respective semiconductor material dies, requiring electrical connections to be provided between the same die and coupling electronic circuits).

[0004] In particular, combined MEMS devices defining an inertial measurement unit (IMU) are known which comprise in the same semiconductor material die at least two different sensors with multiple detection axes (for example at least an accelerometer and a gyroscope), both of three-axis type, to provide information both about the acceleration and the angular velocity of the body or object to which they are applied.

[0005] For example, such devices are widely used in mobile or wearable devices (such as smartphones, tablets, smart watches, etc.) or in automotive or industrial applications.

[0006] In a known manner, accelerometers and gyroscopes comprise respective mobile structures elastically suspended relative to a common substrate formed in a die of semiconductor material and placed in respective sealed cavities, typically defined by bonding a cover to the same substrate; in particular, the cover defines the ceiling of the sealed cavity of the sensing structure of the sensor.

[0007] Furthermore, it is known that different operating conditions need to be defined for the microelectromechanical structures of the combined MEMS device, in particular with regard to different pressure values ​​inside the corresponding sealed cavities. For example, for its optimal operation, an accelerometer requires high pressure values ​​(of the order of several thousand Pa, for example about 0.01 MPa) to damp the corresponding structure, (which is mobile due to inertial effects); whereas a gyroscope requires low pressure values ​​(of the order of several hundred Pa, for example about 100 Pa), again for its optimal operation, to ensure effective actuation of the corresponding mobile structure. Therefore, in this case, the pressure inside the sealed cavity in which the accelerometer is arranged must be different from, in particular greater than, the pressure inside the corresponding sealed cavity in which the gyroscope is placed.

[0008] From the perspective of the manufacturing process, the above process requires defining different pressure values ​​inside the corresponding sealed cavities in the combined MEMS device, which may lead to some implementation problems.

[0009] In this respect, a first known solution envisages the use of a suction zone introduced into at least one sealed cavity (for example coupled to the ceiling of the cover) in order to adjust the pressure in the same sealed cavity in a desired manner.

[0010] Specifically, due to the bonding process and the processing gases used, after bonding the cap to the common substrate, the sealed cavities of the different MEMS structures are at the same pressure; in this case, activating the gettering zone allows reducing the pressure inside the cavity in which the gettering zone is inserted, thereby attracting non-inert gases present in the same cavity.

[0011] Although it is effective to form sealed cavities of a MEMS structure at different pressures, this solution suffers from the potential for crosstalk (ie, mutual interference) between identical sealed cavities.

[0012] In particular, during the bonding process of the cover and the substrate, the gettering zone may also draw gas from cavities where the same gettering zone is not present, thereby modifying the final pressure value of the same cavity.

[0013] In essence, the final pressure value in the cavity may have a certain degree of tolerance relative to the desired pressure set point, and during operation, such tolerance may result in low accuracy of the sensing signal provided by the micro-electromechanical structure.

[0014] A second known solution, described for example in US 10,017,380 B1 or US 9,919,919 B2, envisages defining a "chimney" or access channel through the cover corresponding to at least one sealed cavity (after its bonding to a common substrate), the pressure of which is desired to be controlled differently relative to at least one other cavity.

[0015] Via this access channel, the pressure inside the cavity is adjusted in a desired manner, for example by introducing a gas flow with controlled pressure; thereafter, the same access channel is suitably sealed in the same pressure-controlled environment, for example by deposition or laser melting techniques.

[0016] However, this solution also has some problems. For example, sealing the access channel requires complex additional operations, especially with regard to the laser melting step, which increases the cost and time of the manufacturing process. Summary of the invention

[0017] The present disclosure aims to provide a manufacturing process for a combined micro-electromechanical device that allows to overcome and solve the problems previously highlighted.

[0018] According to the present disclosure, a process for manufacturing a combined micro-electromechanical device and a corresponding combined micro-electromechanical device are provided.

[0019] For example, in at least one embodiment of the manufacturing process disclosed herein, it is summarized as including: forming a sensor wafer of semiconductor material, which has a main surface and at least a first microelectromechanical structure and a second microelectromechanical structure at the main surface; forming a capping wafer, which has a corresponding main surface and at least a first cavity and a second cavity on the corresponding main surface; forming an air suction zone in a local manner inside the first cavity; bonding the corresponding main surfaces of the sensor wafer and the capping wafer in a facing position through an inserted bonding area, so that the first cavity and the second cavity define a first sealed environment and a second sealed environment for the first microelectromechanical structure and the second microelectromechanical structure respectively, and the first sealed environment and the second sealed environment are set to a first pressure value and a second pressure value different from each other, wherein the air suction zone helps to define a first pressure value inside the first sealed environment defined by the first cavity, including: before the bonding step, forming a raised frame so that it is located around the first cavity; wherein during the bonding step, within a time interval before sealing and closing the second cavity, the bonding area determines that the sensor wafer is bonded to the capping wafer at the raised frame and defines a first sealed environment associated with the first cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a better understanding of the present disclosure, preferred embodiments thereof will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0021] Figures 1A to 1G is a schematic cross-sectional view of a combined micro-electromechanical device in successive steps of a corresponding manufacturing process according to an embodiment of the present solution;

[0022] Figure 2 A schematic plan view showing a possible layout of a capping wafer incorporating a micro-electromechanical device;

[0023] FIG. 3A to FIG. 3E are schematic cross-sectional views of a combined micro-electromechanical device in successive steps of a corresponding manufacturing process according to an embodiment of the present solution; and

[0024] Figure 4 is a schematic block diagram of an electronic device including a combined micro-electromechanical device. DETAILED DESCRIPTION

[0025] Generally speaking, and as will be described in detail below, one aspect of the present solution contemplates forming a raised frame at, and particularly around, the cavities where pressure is desired to be controlled by an intake zone, prior to bonding a common substrate having different microelectromechanical structures formed therein to a corresponding cover (which helps define the cavities associated with the microelectromechanical structures).

[0026] In this way, when the cover is coupled to the common substrate, bonding first occurs at the raised frame, thereby sealing the above-mentioned cavity (wherein the other cavities are still open to the external environment); therefore, the air intake zone is activated in a localized manner inside the cavity, thereby reducing the possibility of interference (crosstalk) with other cavities.

[0027] A first embodiment of a combined micro-electromechanical (MEMS) device is now described, envisaging forming the above-described raised frame on a cover before coupling the same cover to a common substrate.

[0028] in this regard, Figure 1A A capping wafer 1 of a semiconductor material (particularly silicon) is shown, which has: a first main surface 1a, which extends parallel to a horizontal plane xy; and a second main surface 1b, which extends in a corresponding horizontal plane, is parallel to the above-mentioned first main surface 1a and is separated from the first main surface 1a along a vertical axis z (this defines a three-dimensional Cartesian reference system with a horizontal plane xy).

[0029] The manufacturing process initially envisages (as a first processing step of the above-mentioned capping) forming a raised frame on the first main surface 1a of the capping wafer 1, around the location that will subsequently be occupied by a first cavity associated with a first microelectromechanical structure of the combined MEMS device. In particular, this first microelectromechanical structure (for example defining a gyroscope) has the need for low operating pressure relative to at least one other microelectromechanical structure of the same combined MEMS device.

[0030] In detail, the above Figure 1A The first step of the manufacturing process shown in provides for forming an etching mask 4 (so-called "hard mask") on the above-mentioned first main surface 1a. For example, this hard mask 4 is defined by forming a silicon oxide (e.g. TEOS) layer on the first main surface 1a, the formation process having an oxidation process and subsequent patterning of the same silicon oxide layer by wet etching.

[0031] Through the hard mask 4, the first main surface 1a of the cap wafer 1 is wet-etched with an anisotropic etching solution (for example, with TMAH (tetramethylammonium hydroxide)).

[0032] like Figure 1BAs shown in , after such etching, a raised frame 6 is formed above the above-mentioned first main surface 1 a at the location of the hard mask 4 , the raised frame 6 having a height, for example, comprised between 3 μm and 5 μm along the vertical axis.

[0033] As will also be discussed below, the raised frame 6 has an annular shape in a cross section parallel to the horizontal plane xy, such as a square, rectangular or generally polygonal annular shape.

[0034] It should be emphasized that Figure 1B (and other figures) only show the portion of the capping wafer 1 dedicated to forming the structure of what will be the first combined MEMS device. Obviously, by means of a sawing operation, the capping wafer 1 is intended to define a plurality of combined MEMS devices, so that for each of said combined MEMS devices, a plurality of raised frames 6 are typically formed above the first main surface 1a during this step of the manufacturing process.

[0035] like Figure 1C As shown in , the manufacturing process then envisages: forming the above-mentioned first cavity, represented here by 8 (designed to be associated with a first microelectromechanical structure of the combined MEMS device (for example defining a gyroscope)) in the capping wafer 1 by dry etching starting from the first main surface 1a; and in addition forming a second cavity 9 (designed to be associated with a second microelectromechanical structure of the combined MEMS device (for example defining an accelerometer)).

[0036] As previously mentioned, the first micro-electromechanical structure is configured to operate at a pressure having a different value (in particular a lower value) relative to an operating pressure of the second micro-electromechanical structure.

[0037] The first cavity 8 and the second cavity 9 extend along the vertical axis z to a desired depth (e.g. equal to 30 μm) inside the capping wafer 1 and are arranged side by side and separated on the horizontal plane xy by a separating portion 7 of the same capping wafer 1 .

[0038] Specifically, Figure 2 As shown in the schematic layout of , the first cavity 8 is formed inside the above-mentioned raised frame 6, which completely surrounds the same first cavity 8 in the horizontal plane xy. In contrast, the second cavity 9 is not surrounded by the raised frame (except for a possible side common to the above-mentioned first cavity 8 if the separation part 7 has a small width in the horizontal plane xy).

[0039] In a manner not illustrated here, structural elements such as, for example, stoppers etc. can possibly be defined inside the first cavity 8 and / or the second cavity 9 by dry etching as described above.

[0040] like Figure 1DAs shown in , the process then envisages depositing, on the first main surface 1 a of the cap wafer 1 , bonding areas 10 of a suitable material for ensuring a hermetic coupling, in particular a paste of a glassy material, the so-called “frit”.

[0041] The bonding area 10 (also as Figure 2 ) is deposited at the side walls of the first cavity 8 and the second cavity 9 to completely surround the same first cavity 8 and the second cavity 9, thereby presenting an annular shape such as a square, a rectangle or a generally polygonal shape on the horizontal plane xy, which surrounds these first cavity 8 and the second cavity 9, as described above Figure 2 As shown in the figure.

[0042] In particular, the bonding area 10 is deposited around the first cavity 8 on the previously formed raised frame 6 , presenting a shape that follows and replicates the shape of the underlying raised frame 6 .

[0043] Therefore, around the aforementioned first cavity 8 , the bonding area 10 has a raised portion 11 (arranged directly above the aforementioned raised frame 6 ) and its overall height along the vertical axis z is therefore greater than the height that the bonding area 10 presents around the second cavity 9 .

[0044] Afterwards, if Figure 1E As shown in FIG. 1 , a getter zone 12 is formed inside the first cavity 8 (the getter zone 12 is confined in the first cavity 8 and does not exist in the second cavity 9). The getter zone may be made of a mixed oxide (eg, zirconium oxide).

[0045] Then, if Figure 1F As shown in , the manufacturing process envisages bonding the cap wafer 1 to the sensor wafer 14 by thermocompression in the direction of the vertical axis z, wherein the above-mentioned first and second microelectromechanical structures have previously been formed in a manner not described in detail here.

[0046] For example, the combined MEMS device defines an inertial measurement unit, the first microelectromechanical structure is a sensing structure defining a capacitive gyroscope (e.g. of the three-axis type), and the second microelectromechanical structure is a sensing structure defining a capacitive accelerometer (e.g. also of the three-axis type).

[0047] The sensor wafer 14 of semiconductor material, for example silicon, has a respective first main surface 14a extending parallel to a horizontal plane xy and a second main surface 14b extending in a respective horizontal plane, parallel to the first main surface 14a and separated therefrom along a vertical axis z.

[0048] When the above-mentioned bonding between the sensor wafer 14 and the cover wafer 1 is performed, the corresponding first main surface 14 a faces the first main surface 1 a of the sensor wafer 1 .

[0049] exist Figure 1F The first and second microelectromechanical structures schematically indicated by 16 , 17 are formed in a first part 14 ′ and a second part 14 ″, respectively, of the sensor wafer 14 , which parts differ from each other at the first main surface 14 a and are separated by a separation part 18 of the same sensor wafer 14 .

[0050] Specifically, after the above-mentioned bonding of the cover wafer 1 to the sensor wafer 14, the first micro-electromechanical structure 16 is arranged at the first cavity 8; similarly, the second micro-electromechanical structure 17 is arranged at the second cavity 9. In a manner known per se, the first cavity 8 and the second cavity 9 contribute to forming a housing cavity, in which the moving elements (e.g. inertial mass blocks) of the above-mentioned first micro-electromechanical structure 16 and the second micro-electromechanical structure 17 are free to move.

[0051] According to one aspect of the present solution, due to the presence of the raised frame 6 and the provision of the bonding area 10 with the raised portion 11 at the same raised frame 6, the above-mentioned bonding of the cover wafer 1 and the sensor wafer 14 is achieved in two steps.

[0052] As mentioned above Figure 1F As shown in FIG. 1 , in the first step, bonding occurs only at the raised frame 6 due to the fact that the first main surface 14 a of the sensor wafer 14 is first brought into contact with the raised portion 11 of the bonding area 10 .

[0053] Thus, a hermetic closure (sealing) of the first cavity 8 is obtained and the getter zone 12 is activated in a sealed environment inside the same first cavity 8 , while the second cavity 9 is still open (bonding around the same second cavity 9 has not yet taken place).

[0054] Advantageously, interference, crosstalk between the first cavity 8 and the second cavity 9 is thus avoided; in other words, the above-mentioned suction zone 12 helps to control the pressure value inside the first cavity 8, but in this case does not affect the pressure value inside the second cavity 9.

[0055] Only in the second step of the bonding, when the first cavity 8 has been sealed and the desired pressure value therein has been determined due to the action of the gettering area 12, the first main surface 14a of the sensor wafer 14 contacts the portion of the bonding area 10 arranged around the second cavity 9.

[0056] like Figure 1G As shown in , therefore, a sealed closure of the second cavity 9 also occurs (wherein the pressure value in the sealed environment inside the same second cavity 9 is completely determined by the operating environment in which the bonding process is performed and is not affected by the above-mentioned gettering zone 12), wherein the two cavities of the combined MEMS device are completely sealed.

[0057] For example, the pressure of the environment in which the bonding process is performed has a high value (for example of the order of thousands of Pa, for example equal to 0.01 MPa), suitable for operating the accelerometer defined by the second micro-electromechanical structure 17 .

[0058] The manufacturing process ends with sawing the stack defined by the bonding of the cap wafer 1 and the sensor wafer 14 to form a combined MEMS device, one of which is Figure 1G In the figure, it is shown and indicated by 20.

[0059] Specifically, the combined MEMS device 20 includes a sensor die 140, which advantageously has both a first microelectromechanical structure 16 and a second microelectromechanical structure 17 therein; and further includes a cover 100 coupled to the sensor die 140, the cover 100 having corresponding first cavities 8 and second cavities 9, which help to define a sealed environment for the above-mentioned first microelectromechanical structure 16 and second microelectromechanical structure 17, which are set to a first pressure and a second pressure, respectively, and the values ​​of the first pressure and the second pressure are different and are optimized for corresponding operations.

[0060] A different embodiment of a process for manufacturing a combined MEMS device is now described, in which the above-mentioned raised frame 6 is not formed on the cover wafer 1 but is formed on the sensor wafer 14 .

[0061] in this regard, Figure 3A An already advanced step of a process for manufacturing the above-described sensor wafer 14 is shown (here shown in more detail with respect to the previous figures).

[0062] Specifically, the sensor wafer 14 includes a substrate 24 having an upper surface 24 a and a dielectric layer 25 formed thereon, and the first micro-electromechanical structure 16 and the second micro-electromechanical structure 17 are to be formed above the substrate 24 .

[0063] A conductive layer 26 (e.g. made of polysilicon) is arranged on the dielectric layer 25 and is suitably patterned so as to define suitable electrical connections between the first microelectromechanical structure 16 and the second microelectromechanical structure 17 and contact pads (not shown here) accessible from the outside of the combined MEMS device, which contact pads are used, for example, for biasing the same structures and for acquiring corresponding sensing signals.

[0064] A sacrificial layer 27 of dielectric material is suitably patterned on the conductive layer 26; a structural layer 28 (e.g. of epitaxially grown polysilicon) is formed above the sacrificial layer 27. The upper surface 28a of the structural layer 28, which is arranged at a certain distance from the substrate 24, defines the above-mentioned corresponding main surface 14a of the sensor wafer 14, which is designed to face the cap wafer 1 after bonding.

[0065] As the same Figure 3B As shown in , a metal layer has previously been deposited above the upper surface 28a and patterned (for example by wet etching) for forming the above-mentioned contact pads, indicated by 30, in the horizontal plane xy at positions outside the area to be occupied by the above-mentioned first microelectromechanical structure 16 and the second microelectromechanical structure 17.

[0066] According to aspects of this embodiment, Figure 3B As shown in , therefore, in this case, a hard mask (again indicated by 4 ) is formed on the above-mentioned upper surface 28 a of the structural layer 28 .

[0067] like Figure 3C As shown in FIG. 2 , the upper surface 28 a of the structural layer 28 of the sensor wafer 14 is then wet-etched with an anisotropic etching solution, for example with TMAH (tetramethylammonium hydroxide), through the hard mask 4 .

[0068] After this etching, a raised frame (again indicated by 6) is formed where the hard mask 4 was located.

[0069] like Figure 3D As shown in , here a trench etch is performed through the entire thickness of the structural layer 28 , which also requires removal of a large part of the underlying sacrificial layer 27 .

[0070] Thus, the formation of the first microelectromechanical structure 16 and the second microelectromechanical structure 17 is completed, these structures including corresponding suspended elements defined in the same structural layer 28, schematically indicated by 29 (for example, inertial mass blocks, sensing electrodes and / or actuating electrodes, elastic elements); these suspended elements 29 are coupled to corresponding anchoring elements 31, which are integral with the substrate 24 and are also defined starting from the same structural layer 28.

[0071] In the illustrated example, the separated portion 18 of the sensor wafer 14 includes a portion of the structural layer 28 .

[0072] In this case, the raised frame 6 having a (square, rectangular or generally polygonal) annular shape therefore directly surrounds the first microelectromechanical structure 16 in the horizontal plane xy.

[0073] The manufacturing process then continues by bonding the sensor wafer 14 to the cap wafer 1, as shown in FIG. Figure 3E As shown in the figure.

[0074] This capping wafer 1 has been previously processed for forming the first and second cavities 8, 9 as previously described and for forming the gettering zone 12 inside the first cavity 8 (unlike previously discussed, the processing of the capping wafer 1 did not envisage defining a raised frame).

[0075] Furthermore, a bonding area 10 has been deposited on the first main surface 1 a of the capping wafer 1 , completely surrounding both the first cavity 8 and the second cavity 9 .

[0076] Likewise, in this case, similar to what was discussed previously, the bonding process provides: a first step in which the bonding area 10 initially contacts the raised frame 6, thereby initially determining the sealing of the first cavity 8 and activating the gettering area 12; and a second step in which the same bonding area 10 contacts the upper surface 28a of the structural layer 28 around the second cavity 9, thereby also determining the sealing of the second cavity 9.

[0077] As previously described, the manufacturing process ends with sawing the stack formed by the sensor wafer 14 and the cap wafer 1 to define individual combined MEMS devices 20, each of which includes a sensor die 140 and also includes a cap 100 coupled to the sensor die 140 (as described above). Figure 3E ).

[0078] The advantages of the present solution are clear from the preceding description.

[0079] In any case, it is emphasized that the described solution allows to reduce (in particular substantially eliminate) the crosstalk between the microelectromechanical structures 16, 17 of the combined MEMS device 20, without requiring substantial changes to the manufacturing process flow. In general, the described solution actually requires the addition of a single hard mask to define the raised frame 6 at the first cavity 8 associated with the first microelectromechanical structure 16.

[0080] The described process is therefore simple and inexpensive to implement, without requiring complex and expensive additional process steps to achieve different pressure values ​​for the sealed cavities of the microelectromechanical structures 16 , 17 of the combined MEMS device 20 .

[0081] The discussed solution is advantageously applicable to electronic devices, for example portable type electronic devices (such as smartphones, tablets, smart watches), such as Figure 4 As shown schematically in FIG.

[0082] The electronic device (indicated by 40 ) comprises: a combined MEMS device 20 , for example acting as an inertial measurement unit; and a control unit 42 operatively coupled to the combined MEMS device 40 for receiving sensing signals provided by the same combined MEMS device 20 , thereby controlling the general operation of the electronic device 40 .

[0083] Finally, it is evident that modifications and variations may be made to what has been described and illustrated without thereby departing from the scope of the present disclosure as defined in the appended claims.

[0084] In particular, it is emphasized that the described solution may find advantageous application in all MEMS devices in which it is necessary to provide at least two structures with corresponding different sealed cavities in which different pressure values ​​are to be defined (for example the solution may be applied in the case of a combined MEMS device comprising two accelerometers or two gyroscopes and / or any other sealed cavity structure, such as a microphone or a pressure sensor).

[0085] At least one embodiment of a process for manufacturing a combined microelectromechanical device (20) of the present disclosure is summarized as comprising: forming a sensor wafer (14) of semiconductor material having a main surface (14a) and at least a first microelectromechanical structure (16) and a second microelectromechanical structure (17) at the main surface (14a); forming a capping wafer (1) having a corresponding main surface (1a) and at least a first cavity (8) and a second cavity (9) at the corresponding main surface (1a); forming a gettering area (12) in a localized manner inside the first cavity (8); bonding the corresponding main surfaces (14a, 1a) of the sensor wafer (14) and the capping wafer (1) in a facing position through an interposed bonding area (10) so that the first cavity and the second cavity (8, 9) are respectively A first sealed environment and a second sealed environment are defined for the first micro-electromechanical structure and the second micro-electromechanical structure (16, 17), and the first sealed environment and the second sealed environment are respectively set to first pressure values ​​and second pressure values ​​different from each other, wherein the suction area (12) helps to define a first pressure value inside the first sealed environment defined by the first cavity (8), and the embodiment is characterized in that it includes: before the bonding step, a raised frame (6) is formed so that it is located around the first cavity (8); wherein during the bonding step, within a time interval before the second cavity (9) is sealed and closed, the bonding area (10) determines that the sensor chip (14) is bonded to the cover chip (1) at the raised frame (6) and defines a first sealed environment associated with the first cavity (8).

[0086] In at least one embodiment, the process includes: forming a bonding area (10) to completely surround both the first cavity (8) and the second cavity (9); wherein the bonding step includes: a first phase, in which the bonding area (10) determines the sealed closure of the first cavity (8) and the subsequent activation of the gettering area (12); and a second phase, temporally consecutive to the first phase, in which the bonding area (10) brings the corresponding main surfaces (14a, 1a) into contact around the second cavity (9), thereby determining the sealed closure of the second cavity (9) and the definition of a second sealed environment.

[0087] In at least one embodiment, a second pressure value inside the second sealed environment defined by the second cavity (9) is greater than a first pressure value inside the first sealed environment defined by the first cavity (8).

[0088] In at least one embodiment, the second pressure value is limited only by the pressure of the operating environment associated with the bonding step.

[0089] In at least one embodiment, the raised frame (6) is formed by etching the capping wafer (1) through a mask (4) on the main surface (1a) in such a way as to be located around the first cavity.

[0090] In at least one embodiment, the process includes: forming the bonding area (10) around the first cavity (8) at least partially above the raised frame (6); thereby, around the first cavity (8), the bonding area (10) has a configuration having a raised portion (11) arranged on the raised frame (6) and a total height along a vertical axis (z) orthogonal to the main surface (1a) of the cover wafer (1), which is greater than the height of the bonding area (10) presented around the second cavity (9).

[0091] In at least one embodiment, the raised frame (6) is formed by etching the sensor wafer (14) through a mask (4) on the main surface (14a) in such a way as to be located around the first sensing structure (16).

[0092] In at least one embodiment, the sensor wafer (14) includes a substrate (24) and a structural layer (28) above the substrate (24), the structural layer (28) having an upper surface (28a) defining the corresponding main surface (14a) of the sensor wafer (14); wherein the raised frame (6) is formed on the upper surface (28a) of the structural layer (28), and the step of forming the second sensing structure (17) includes: etching the structural layer (28) from the upper surface (28a) to the inside of the raised frame (6) to form a suspended element (29) above the substrate (24).

[0093] In at least one embodiment, the bonding area (10) includes a glass frit material.

[0094] In at least one embodiment, the first microelectromechanical structure (16) defines a gyroscope sensor and the second microelectromechanical structure (17) defines an accelerometer sensor.

[0095] At least one embodiment of the combined micro-electromechanical device (20) of the present disclosure is summarized as comprising: a sensor die (140) of semiconductor material, having a main surface (14a) and integrating at least a first micro-electromechanical structure (16) and a second micro-electromechanical structure (17) at the main surface (14a); a cover (100) having a corresponding main surface (1a), wherein at least a first cavity (8) and a second cavity (9) are formed at the corresponding main surface (1a), and a gettering area (12) is arranged in a local manner inside the first cavity (8); wherein the corresponding main surfaces (14a, 1a) of the sensor die (140) and the cover (100) are connected by an interposed bonding area (1 0) are bonded in a facing position so that the first cavity and the second cavity (8, 9) define at least a first sealed environment and a second sealed environment for the first micro-electromechanical structure and the second micro-electromechanical structure (16, 17), respectively, and the first sealed environment and the second sealed environment are respectively set to a first pressure value and a second pressure value different from each other, and the embodiment is characterized in that it also includes a raised frame (6) located around the first cavity (8); wherein the bonding area (10) is inserted between the main surfaces (14a, 1a) of the sensor die (14) and the cover (100) at the raised frame (6) to define the first sealed environment associated with the first cavity (8).

[0096] In at least one embodiment, the bonding area (10) completely surrounds the first cavity (8) and the second cavity (9).

[0097] In at least one embodiment, the bonding area (10) includes a portion inserted around the first cavity (8) between the raised frame (6) and one of the main surface (14a) of the sensor die (14) and the main surface (1a) of the cover (1).

[0098] In at least one embodiment, the bonding area (10) includes a glass frit material.

[0099] In at least one embodiment, the first microelectromechanical structure (16) defines a gyroscope sensor and the second microelectromechanical structure (17) defines an accelerometer sensor; and a second pressure value inside a second sealed environment defined by the second cavity (9) is greater than a first pressure value inside a first sealed environment defined by the first cavity (8).

[0100] The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to provide further embodiments using concepts of various patents, applications, and publications.

[0101] 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 interpreted to limit the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full range of equivalents to which such claims are entitled. Therefore, the claims are not limited to the present disclosure.

Claims

1. A method for manufacturing a combined micro-electromechanical device, comprising: forming a sensor wafer of semiconductor material having a major surface and at least a first microelectromechanical structure and a second microelectromechanical structure at the major surface; forming a capping wafer having respective major surfaces and at least a first cavity and a second cavity at the respective major surfaces; locally forming a suction zone within the first cavity; The corresponding main surfaces of the sensor wafer and the cover wafer are bonded in a facing position by interposing a bonding area, so that the first cavity and the second cavity define a first sealed environment and a second sealed environment for the first micro-electromechanical structure and the second micro-electromechanical structure, respectively, the first sealed environment and the second sealed environment are set to a first pressure value and a second pressure value different from each other, wherein the getter area helps to define the first pressure value inside the first sealed environment defined by the first cavity, The method comprises: before the bonding step, forming a raised frame so that the raised frame is located around the first cavity; Wherein during the bonding step, within a time interval before sealingly closing the second cavity, the bonding area determines bonding of the sensor wafer to the cover wafer at the raised frame and defines the first sealed environment associated with the first cavity.

2. The method according to claim 1, comprising: forming the bonding region to completely surround the first cavity and the second cavity; wherein said bonding step comprises: a first phase wherein said bonding zone determines said hermetic closure of said first cavity and subsequent activation of said getter zone; and a second phase, temporally consecutive to said first phase, in which said bonding zones bring said corresponding main surfaces into contact around said second cavity, thereby determining the hermetic closure of said second cavity and said definition of said second sealed environment. 3 . The method of claim 1 , wherein the second pressure value inside the second sealed environment defined by the second cavity is greater than the first pressure value inside the first sealed environment defined by the first cavity. The method of claim 3 , wherein the second pressure value is limited only by the pressure of an operating environment associated with the bonding step. 5 . The method according to claim 1 , wherein the raised frame is formed by etching the capping wafer through a mask on the main surface in such a manner as to be located around the first cavity.

6. The method according to claim 5, comprising: forming the bonding area around the first cavity at least partially over the raised frame; Thus, around the first cavity, the bonding area has a configuration having a raised portion arranged on the raised frame and a total height along a vertical axis orthogonal to the major surface of the cover wafer, the total height being greater than the height presented by the bonding area around the second cavity. 7 . The method according to claim 1 , wherein the raised frame is formed by etching the sensor wafer through a mask on the main surface in such a manner as to be located around the first sensing structure.

8. The method of claim 7, wherein the sensor wafer comprises a substrate and a structural layer above the substrate, the structural layer having an upper surface defining the corresponding major surface of the sensor wafer; wherein the raised frame is formed on the upper surface of the structural layer, and the step of forming the second sensing structure comprises: The structural layer is etched from the upper surface to the inside of the raised frame to form a suspended element above the substrate.

9. The method of claim 1, wherein the bonding region comprises a frit material.

10. The method of claim 1, wherein the first microelectromechanical structure defines a gyroscope sensor and the second microelectromechanical structure defines an accelerometer sensor.

11. A combined micro-electromechanical device comprising: a sensor die of semiconductor material, the sensor die having a main surface and integrating at least a first microelectromechanical structure and a second microelectromechanical structure at the main surface; a cover having respective major surfaces at which at least a first cavity and a second cavity are formed, a getter zone being arranged in a localized manner inside the first cavity; wherein the respective main surfaces of the sensor die and the cover are bonded in a facing position via an interposed bonding region so that the first cavity and the second cavity define at least a first sealed environment and a second sealed environment for the first micro-electromechanical structure and the second micro-electromechanical structure, respectively, the first sealed environment and the second sealed environment being set to first and second pressure values ​​different from each other, respectively, wherein by further comprising a raised frame located around said first cavity; Wherein the bonding area is interposed between the major surface of the sensor die and the major surface of the cover at the raised frame to define the first sealed environment associated with the first cavity.

12. The apparatus of claim 11, wherein the bonding region completely surrounds both the first cavity and the second cavity. 13 . The apparatus of claim 11 , wherein the bonding area includes a portion around the first cavity interposed between the raised frame and one of the major surface of the sensor die and the major surface of the cap.

14. The apparatus of claim 11, wherein the bonding region comprises a frit material.

15. The device of claim 11, wherein the first microelectromechanical structure defines a gyroscope sensor and the second microelectromechanical structure defines an accelerometer sensor; and wherein the second pressure value inside the second sealed environment defined by the second cavity is greater than the first pressure value inside the first sealed environment defined by the first cavity.

16. A method comprising: forming a sensor wafer of semiconductor material having a first major surface and at least a first microelectromechanical structure and a second microelectromechanical structure at the first major surface; forming a raised frame on the second major surface of the cover wafer; After forming the raised frame, forming at least a first cavity and a second cavity, the first cavity and the second cavity extending into the second major surface of the capping wafer, the raised frame extending around the first cavity; After forming at least the first cavity and the second cavity, forming a bonding area on a remaining portion of the second major surface and on the raised frame; After forming the bonding region, forming a getter region lining a corresponding surface of the capping wafer, the surface defining the first cavity; as well as The sensor wafer is coupled to the bonding area, the first microelectromechanical structure is aligned with the first cavity, and the second microelectromechanical structure is aligned with the second cavity.

17. The method of claim 16, wherein forming the raised frame comprises: A corresponding portion of the raised frame is formed between the first cavity and the second cavity. The method of claim 16 , wherein the first cavity is devoid of the suction zone.

19. The method of claim 16, wherein the suction zone helps define a first pressure value inside a first sealed environment defined by the first cavity, the first pressure value inside the first sealed environment being different from a second pressure value inside a second sealed environment defined by the second cavity.

20. The method of claim 19, wherein the second pressure value is greater than the first pressure value.

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